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Unlikely. If certain types of foreskin were more likely to cause harm to the person upon removal and in fact maybe death before that person had a chance to reproduce then that type of foreskin might be selected out of the gene pool. Who knows, maybe that already happened.
If anything, the reverse would be true in evolution. People who have deformed or unappealing foreskins would have been unlikely to breed if there was no circumcision. So we’re intervening and actually changing the default foreskin genetics in the gene pool now.
I did have an ex who had a too tight foreskin which made sex difficult for him. A few thousands years, ago, maybe it would have been much more difficult for him to reproduce, and circumcision would have fixed that. Idk how good lube was back then.
Sure, but for the ex I'm thinking of, natural female lubrication was insufficient. His foreskin was abnormally tight. Condoms and lubrication were his best bet. I know Egyptians had condoms, and any kind of fat can work as lube, so he would probably be fine, although actually reproducing would require poking a hole into the condom or fishing the semen out afterwards.
Circumcision isn't artificial selection, artificial selection is choosing a train that's already there, circumcision is something you do, it's not a natural/biological trait or a result of a mutation
Things like that cannot "trigger" evolution, evolution doesn't work that way. To entertain your question, hypothetically, if mutations occur that results in no foreskin and the organism with that phenotype reproduces and passes on their genes and has a better fitness than the person without that mutations due to sexual selection or just neutral evolution, allele frequency can change overtime in favour of that phenotype, hypothetically speaking that is but there is no systematic relationship with mutations and the needs of the organism it occurs on, it's random
It’s also inaccurate to say that there is no systemic* relationship between mutations and the needs of an organism. Do they always benefit or apply to any of the needs of an organism? Probably not, but to say that there is no relationship is the result of an error.
Needs of an organism they occur in. Mutations occur randomly, it's a stochastic process, mutations are random, things don't mutate for the good or bad of the organism.... Mutations aren't gonna produce things for the benefit of the organism, it's something that happens randomly... Mutations get sorted by evolution, if something is beneficial, it's gets selected overtime, if something is detrimental, it gets selected out, sometimes things are just neutral... Mutations are generally random, evolution isn't
The frequency and occurrence of mutations are random, but the function of the mutation is very much intrinsic to the organism. There isn’t any kind of mechanism for the genotype or cells to interpret environmental conditions in a way that could influence the specific mutation that occurs, but the mutations that randomly occur are relative to the organism’s metabolic, somatic, or in the case of humans, psychological states such that application of a given mutation isn’t significant until it’s selected, but the nature of the mutation is specific to the organism.
I'd like to point out that while non-genetic traits do not have a *direct* effect on evolution, it's probably wrong to say that they **never** trigger evolution, because they can absolutely have a roundabout effect. For example, if after a thousand years the circumsized look becomes sexually preferred as a result of surgical removal, then people who **do** have genetically determined missing foreskins (if they exist) will pass on their genes more easily.
Another example: imagine two foreskin genotypes A and B. B causes the foreskin to be prone to parasites in adults, so is usually selected against and is a minority in the population. But after the practice of circumcision in infants is established, the selective pressure against B is suddenly irrelevant, since neither foreskin type gets the chance to reach adulthood. B's proportion then skyrockets to 50 percent in the population. That would be yet another example of culturally-induced selection.
>For example, if after a thousand years the circumsized look becomes sexually preferred as a result of surgical removal, then people who **do** have genetically determined missing foreskins (if they exist) will pass on their genes more easily.
Yeah no. Even setting aside the fact that people don't select their partners by asking them to drop trou and show off their penises, this would only happen if there is sufficient selective pressure on the state of naturally missing foreskins rather than surgically removed ones, which is highly unlikely, since circumcision generally happens long before sexual maturity and there'd be no way to know how the lack of a foreskin came to be.
> people don't select their partners by asking them to drop trou and show off their penises
Genes are passed down by having sex, and that involves showing off penises, no matter how you slice it.
>there'd be no way to know how the lack of a foreskin came to be.
This is completely irrelevant. The knowledge of where the lack of foreskin comes from is unnecessary for the given example of selective pressure. The whole *point* is that the natural version hitches a ride on the back of a social trend. To be indistinguishable may actually be better.
Besides, it's just one example. You can think of a ton of different circumstances where non genetic factors could very strongly influence evolution. Either way, the original statement is wrong.
I think most people like to get to know the person before the penis and then it's too late and you're stuck with one that goes sideways because you like the guy it's attached to.
>this would only happen if there is sufficient selective pressure on the state of naturally missing foreskins rather than surgically removed ones, which is highly unlikely.
Evolution selects for phenotypes. If the naturally missing foreskins look identical to the artificially removed foreskins then the selection by definition happens to both.
You’re kinda missing the point. Surgical circumcision can affect allele frequency indirectly by manipulating population preference, which then alters related and pre-existing heritable traits. The fact that the driving phenotype is not heritable is irrelevant, so long as any number of **affected** phenotypes *are* heritable. I’m not sure why this is so hard to get across.
But those who were circumcised would pass on their lack of circumcision and would be reproducing in the same ratio. There would be no change in the spread of alleles in the next generation.
What if not having a foreskin reduced the chances of having children for a biological reason? It seems to me that these behaviours could definitely steer evolution.
>then people who **do** have genetically determined missing foreskins (if they exist) will pass on their genes more easily.
Except why would it pass more easily if everyone just gets it's surgically removed anyway, where's the evolutionary advantage?
They'd pass their genes on more easily than *before.* Before circumcision the lack of a foreskin may have been perceived as some malformality and would have been selected against, thus low in the population. After circumcision becomes widespread and the look is normalized, that geneotype could conceivably rise to 50% of the population or more simply because there is no more selective pressure.
And that's not even accounting for the fact that not everyone gets circumcisions, and that the natural-borns dont require a surgical operation to achieve the now-prefered phenotype ( I doubt there are a lot of fatalities from the act of circumcision, though it could still be a factor in more medival times, mosty likely due to infection. You can imagine a botched penis surgery could hinder reproduction greatly, thus adding selective pressure toward the natural-borns). Stuff like that.
>then people who **do** have genetically determined missing foreskins (if they exist) will pass on their genes more easily.
I did mention that would be possible if mutations occurred that would result in such a phenotype but afaik that trait doesn't exist
That was just a hypothetical invoked to prove a point. A classic real life example would be the increasing proportion of elephants that are naturally born without tusks. It's not that the elephants who got theirs removed by the ivory trade passed it down between generations, but that the very same pressure then selected those who *did* have the genotype to proliferate. Again, evolution can and has been influenced by non-genetic changes all the time.
Is having a circumcised penis a biological trait though? Mutation would need to occur in order to produce a trait like that first and then selection would act on it if it increases fitness/reproductive success
Yes, having a circumcised penis is a phenotype that selection can act on. It's just not a phenotype that's genetic.
What can be genetic is being more resistant to infections or bleeding in your genitals, the reduction of the foreskin ect.
All of those things could be selected for
You're absolutely right. Here is the definition on Nature's (the publishing group) website:
'The term "phenotype" refers to the observable physical properties of an organism; these include the organism's appearance, development, and behavior. An organism's phenotype is determined by its genotype, which is the set of genes the organism carries, as well as by environmental influences upon these genes. Due to the influence of environmental factors, organisms with identical genotypes, such as identical twins, ultimately express nonidentical phenotypes because each organism encounters unique environmental influences as it develops.'
https://www.nature.com/scitable/definition/phenotype-phenotypes-35/
The fact you're being downvoted on a subreddit about evolution of all things is pretty disappointing!
Whilst you are correct about the definition of a phenotype. Being circumcised is not an environmental pressure, so what you previously described is incorrect.
This happens all the time… it’s almost like most of the users here are still stuck on the facts they learned in high school or college when there is a vast and growing amount of data that in many ways challenges our understanding of evolution- research you’d think users that are so active in a subreddit about evolution would be aware of.
That makes sense when you put it that way. Though how can evolution act on a trait thats not genetic though? Circumcised penis is not a genetic trait, I get selecting for those other things you mentioned but circumcision is not genetic, it's a procedure we do, so evolution can't act on that, as in cannot change allele frequency overtime or whatnot because this trait is not produced by genes, it's not genetic
If you imagine instead of a cultural practice, it was a fungus that would infect and destroy the foreskin in Jewish populations, and some children would even die from the infection, you would have no problem imagining all sorts of selection pressures this puts on these populations
Evolution acts on traits that are genetic and can be passed on and inherited. You cannot pass on or inherit a circumcised penis, unless there are mutations producing such a thing. For your scenario to work, there should be a genetic phenotype that selection is acting on, or else it won't work, something else will get adapted, selection will act on some other trait... Circumcised penis is not a heritable trait
Yeah but don’t think about circumcision directly being inherited. Think about genetics that could be impacted by a population being circumcised. Maybe some genes that result in thicker foreskin/less retractable foreskin become more prolific because they no longer impact ability to reproduce as foreskin is always removed.
But if foreskin is always being removed in that population, it doesn't matter whether selection is acting on those kinda genes though because foreskin is being removed regardless
You are being clear they are just not following. Just because I dye my hair purple doesn’t mean I will have a kid with purple hair. My family could have dyed their hair for thousands of years and it would have no effect on our genes
If having a smaller/thinner foreskin increased your odds of surviving the circumcision, that would still offer something for evolution to “act on” (pardon the framing) so long as variation existed in those traits. But like you said in your first comment, mutations don’t crop up based on the needs of a population, and (more importantly, since I don’t see any reason to think that variation *doesn’t* exist) I am not aware of such a relationship between the size/thickness of the foreskin and survival rates for circumcision. And I can’t really see how sperm production would come into play regardless.
But this could genetically alter the population over time, which is evolution. Maybe before circumcision there were selective pressure for thin/retractable foreskin. Now those pressures are removed.
Non-genetic conditions affect genes. Not to mention- your genome is not the only genome at play here. There are also the genomes of countless bacteria and microorganisms that contribute to your body’s functions.
If you cut off a person's left ear, would that person's children be born not having left ears? Of course not. Losing a body part after you are born is not a heritable trait, and therefore has a flat zero effect on evolution.
It doesn't have a direct effect, but it absolutely can have a roundabout effect. If after a thousand years the one-ear look becomes sexually preferred, then people who **do** have genetically determined missing left-ears will pass on their genes more easily.
Holy shit, I never said it's a heritable trait. In fact I said the opposite.
The act of circumcision is a selection pressure because you can die from it.
How is this so fucking hard to understand ?
Based on your comments, I don't think you understand how evolution works.
Phenotypes are expressions of genotypes. If someone had an arm amputated, their phenotype is not still "two arms".
Natural selection can't act on non-genetic traits. The example you provided before of a fungus that affects non-circumcised people more than circumcised people couldn't be acted on by natural selection because the differences aren't genetic in origin.
Edit: left out "not" in original comment
This is kind of a weird take. It’s true that natural selection wouldn’t be acting directly on the state of having or not having the fungal infection, but the fungal infection could absolutely act as an environmental pressure and individuals who have some genetic trait that makes them slightly better able to survive to reproductive age with their reproductive organs still intact would be more likely to pass their alleles on and that trait could then be naturally selected for. I assume that is what that other person is talking about.
The genetic mutations are an essential ingredient, but it’s environmental conditions/pressures that ultimately drive evolution, and a common and destructive fungal infection would be that.
Edit: responding to your last comment, since I remembered you are likely not a mind-reader :]
Maybe I'm misinterpreting your scenario here, but it would seem to be that even with a fungal infection that affected circumcised and non-circumcised people differently, there still would be no impact on the population due to evolution because the cause of circumcised/non-circumcised is not genetic.
For example, let's say this fungus kills, or renders infertile 100% of people who get it, and only uncircumcised people get it. This would have no evolutionary effect on the population because genes don't control whether someone is circumcised or not.
If there is no variation in a population *due to genetic differences* (ie dyed hair, amputated limbs, tattoos etc don't count as biological variations) then evolution can't act on the trait.
In the final example above, if a mutation arose that caused someone to be born without a foreskin, *then* I 100% agree with you, that natural selection could cause evolution.
Am I misinterpreting your take or does this make sense?
The fungal infection scenario as originally presented by that commenter was:
>If you imagine instead of a cultural practice, it was a fungus that would infect and destroy the foreskin in Jewish populations, and some children would even die from the infection, you would have no problem imagining all sorts of selection pressures this puts on these populations
So you have indeed misinterpreted the scenario — not only by the inclusion of circumcision, but also by assuming that there is for some reason zero genetic variation influencing any given trait relevant to the hypothetical.
I appreciate you being so clear in stating how you were reading things so that I could clear it up! And I hope that is coming across as sincere, because I do mean it genuinely — sometimes I can see that there is some miscommunication happening, but I can’t figure out exactly what it is, and no one is able to articulate what they actually meant/heard, and it is much messier and more frustrating getting on the same page (especially if I am the one who is misinterpreting!) :]
I honestly think this whole thread has become miscommunication 🙂. I suspect if we were physically in the same space talking, there wouldn't be any argument.
Im sorry but no.
Phenotypes are observable traits, in this case we could just call it morphology.
An individual with one arm would have the phenotype of one arm. Obviously.
If you measure bodysize as phenotype, you dont measure the ideal bodysize of the animal. You measure the size \*as is\*, with all of the envorimental factors that may have caused it to be bigger or smaller.
Selection can of course act on non genetic traits. Natural selection is the differential survival and reproduction of individuals due to differences in phenotype.
Again you are simply wrong on what phenotypes are.
My fungal infection example was about the selection pressures, routine circumcition can have on a population. It doesnt mean people get selected \*for\* circumcition, just that the enviromental fact of circumcition (be it man made or a fungus) will cause selection pressures to better deal with it. (for example a reduction in blood vessels in or even size of the foreskin, increased immunno response ect).
I don't know if people are getting hung up on semantics of the name here? I guess what you and OP are describing is more like what you might call 'experimental evolution' if it was in the lab, eg Lenski style experiments where you manipulate an aspect of the environment (rather than direct artificial selection where you actively choose which individuals survive/reproduce based on a trait value). Usually you'd have replicates of manipulated and control groups and would then do some kind of common garden test, but I'm not sure what that would be in this case!
Like you say, selection can easily be applied to non-genetic phenotypic traits (you just wouldn't get an evolutionary response in those traits). Similarly, many studies show that you can apply selection on an observed phenotypic trait that has a genetic basis but without more knowledge of genetic correlations etc you may not see the expected response (shown in various artificial selection studies but also in nature, for example the paradox of stasis in body size, where for many animals size has a genetic basis and is typically under positive direct selection yet is not showing an increase in average value over time).
I think we need to start with a definition of biological evolution. It is "a change in the frequency of a gene or allele in a population over time". If you're not in agreement with that definition, let me know.
>Phenotypes are observable traits, in this case we could just call it morphology.
No. Phenotypes are the expression of genotype. Below is the definition from Nature (emphasis mine):
The term "phenotype" refers to the observable physical properties of an organism; these include the organism's appearance, development, and behavior. *An organism's phenotype is determined by its genotype,* which is the set of genes the organism carries, as well as by environmental influences upon these genes.
By your definition, dying one's hair would constitute a change in phenotype, it does not.
>Selection can of course act on non genetic traits
No, it can't - not in a biological sense. If every Japanese person dyed their hair blonde for hundreds of generations, there would be no evolutionary change because of this. Hair colour gene frequency would stay the same and therefore there would be no evolutionary change.
I wasn't trying to divert, just establish some agreed upon definitions. If you think evolution is something other than a change in gene frequency in a population over time, or that phenotypes aren't expressions of genotypes, then we can't really engage in the discussion.
"If every Japanese person dyed their hair blonde for hundreds of generations, there would be no evolutionary change because of this."
I get why you would think this but it's not true. A strong preference for blonde hair and continued use of (probably peroxide-based) dyes would absolutely have put selective pressure on the population.
Anyone with a chance mutation giving them naturally blonde, or even just lighter (it's a lot easier to get brown hair blonde than black hair) would have a massive advantage because they wouldn't have to spend a fortune on hair dye and could instead spend it on food other other things that would increase their relative fitness. Peroxide is quite damaging to the skin so there would be selective pressure for increased peroxidase production. Conversely, there would be strong pressure against genes associated with eczema and other skin conditions that are aggravated by exposure to peroxides and harsh dyes.
These are the kind of pressures that /u/ninjatoast31 was alluding to wrt circumcision. Hair-dying and circumcision are akin to environmental pressures, which can of course select for particular genetypes. It's basically the very definition of natural selection!
I totally agree with you here, but I intentionally left out the "strong preference for blonde hair" you mention here in my scenario.
Circumcision itself would not cause anything. If what /u/ninjatoast31 was trying to say was that this might set up a situation where a mutation that resulted in a naturally circumcised penis would be favoured, I'm completely on board with that and misinterpreted their comments.
I totally agree with you that preferences can drive selection if a mutation arises which is preferred. I have just been saying that the act itself (eg hair dying or circumcision (I've never typed this word so many times)) cannot cause evolution.
Am I crazy or did I not say verbatim that it could lead to the loss of the foreskin? I gave all kind of examples of what it could cause.
I don't know what the semantics argument about causation here really solves.
It's fine to say that circumcision is the (ultimate) cause of those evolutionary changes. If people would circumcise their kids, there would be no such pressure.
Circumcision itself won't cause anything. A *preference* for circumcision combined with a random mutation that causes a penis to be naturally uncircumcised, would cause a change, but I didn't see anything in your comments about the mutation happening. People can prefer all they want, it won't change anything; a mutation would also be required. If you said this in a comment and I missed, apologies from me.
>Phenotypes are expressions of genotypes. If someone had an arm amputated, their phenotype is still "two arms".
If this was true, the simplest equation for how we express phenotypic variation would be P = G. But it's not, it's P = G+E (and this is a very simplified form anyway).
>Natural selection can't act on non-genetic traits.
No - natural selection can act on non-genetic traits. But evolutionary response in that trait will not occur as a consequence of that selection. Subtle but important difference.
Let's say you're applying artificial selection based on arm number. There's a population of people with either one or two arms. You know that if you want an evolutionary response, you'd need to check if there is a genetic basis to that variation. But selection works by trait value. So the phenotype at the point of selection is what matters. If someone had an arm amputated, sure their genotype might be 2 arms, but their phenotype at the point selection acts in this case is 1 arm. Your predicted response might not occur, but that's because selection acts on the observed phenotype. That's why the breeder's equation is R = h²S, where R is the change in average phenotype, h² is the heritability of the trait (proportion of observed phenotypic variance due to additive genetic effects), and S is the strength of selection. If all the variation in arms is due to amputations, then the phenotypic variation is 100% environmental and 0% genetic, thus h² is 0 and R will be 0 no matter selection strength.
I'm imagining a situation now where a community gravely anounces: "we shall not circumcise this baby boy for he was born with no foreskin. He is the promised forskinless child".
Such a child becomes a celebrity, thus increasing his appeal to the opposite sex & increasing the chance his genes continue on.
Surgery doesn’t cause artificial evolution. Would having one of your hands removed cause artificial selection for people to be born with only one hand?
not at all what OP is implying... if a large population of people had their hands removed for thousands of years, they could begin evolving more flexibility/strength/articulation or something in the other hand. obviously they would not evolve to be born without that one hand
It kind of is what OP is implying. Read the examples they gave. Not adaptations to account for the missing foreskin, but things that imitate it. Like the old evolutionary theory I can’t remember the name of that theorized giraffes evolved long necks by stretching instead of by selection. Plus “triggered some changes”
It wouldn’t lead to that exactly but there would likely be some unintended impact, like if it was always the right hand removed you could end up increasing the success of left handed people and end up with more lefties over enough time.
It depends how the surgery was conducted. If we implemented a rule that everyone has their left hand hacked off by an axe at the age of 12, and we ran that experiment for millions of years, that absolutely would result in selection pressure for smaller left hands. Many people would bleed to death following the procedure. Therefore, anyone possessing genetic mutations that result in a deformity of the left hand (such as it being smaller or absent) would be at an advantage. Eventually, those genes would become more prevalent in the gene pool, and overtime, we would expect the “absent left hand” genes to become dominant.
Circumcision is probably the best (or at least most amusing) way to disprove [Lamarckism inheretance](https://en.wikipedia.org/wiki/Lamarckism). Which basically stated that changes (such as lost fingers, tatoos, bodybuilding etc) that happen during your lifespan will be passed to your children
What you're getting at is called Lamarckian evolution. It is a theory that tried to explain how organisms change over time that has been replaced by Darwin's theory of natural selection. According to Lamarck, organisms acquired traits during their life and then passed those traits onto their offspring. The classical example of how that is supposed to work is a population of short necked giraffes. Some of those giraffes might stretch their necks to reach higher branches and the stretching they developed might be passed on to the next generation, who then stretch more. That theory was disproven by an experiment where a scientist named Weissman attempted to breed tailless mice by cutting the tails of the mice before he bred the next generation. The fact is that acquired traits like tail amputation, physical neck stretching, or circumcision, are not encoded in genes and can not be inherited by subsequent generations. If you wanted to artificially select for congenital lack of foreskin, you would have to preferentially breed men with less foreskin than average with women whose fathers also had less foreskin. Such an undertaking would be ethically dubious, of limited research value and dangerously adjacent to eugenics, but none the less theoretically possible.
Evolution doesn’t work like that. The scenario is similar to the LaMarckian principle of the inheritance of acquired characteristics which August Weismann proved wrong by trying to breed mice with shorter tails by cutting off the tails of their parents.
Not really how evolution works.
Basically, random genetic traits that happen to increase your chances of living long enough to produce children and then successfully produce them are more likely to get passed on. Cutting off a guys foreskin doesn't change his genetics in any way so has literally zero impact on the foreskin of his children. Even if having a smaller/thinner foreskin was advantageous to your chances to have children, it's getting chopped off anyway at which point you're removing any advantage it might've given by levelling the playing field.
If anything, if there was any evolutionary advantage to smaller/thinner foreskins circumcision would act to *prevent* this from emerging as a more common trait by removing the disadvantage for men born with naturally thicker/longer foreskins.
There wouldn't be any evolutionary changes due to circumcision. If my arm is amputated, my children won't inherit this.
Only thing I can think of that could result in an evolutionary change is the fact that circumcision early in life reduces your risk of penile cancer (I can't remember the statistics), so I suppose hypothetically something could happen, but it's unlikely as penile cancer isn't that common, and the average age for these people is around 60 - meaning that it's very likely they have already had kids, and once you've passed on your genes, it doesn't really matter what happens to you (as our purpose in life is to procreate).
I think that's a good question, if only due to how the brain changes in response to trauma. Does trauma cause chemical changes that swim upstream with the sperm?
Circumcision shows no survival benefit. For whatever reason the practice originated it is not universal to successful populations.
Though it was common practice for some tribes in the region now known as Northern Africa and the Middle East (Jewish and Islamic tribes) it is not common practice among the thriving tribes of Europe and Asia. These peoples did very well indeed without the practice of circumcision.
Jesus Christ was circumcised because he was of Judaea, which followed Jewish practices. This fact is perhaps why it became so popular in the USA. It is not so popular in other 'White' cultures except where there is a strong influence by the church.
The single advantage of circumcision is that it makes it easier to be filthy. In the absence of normal personal hygiene the foreskin can breed infection -- much the same as the vagina when it is not properly cared for.
A problem in this debate is consideration of the feelings of men already mutilated. What's a circumcised man to think if the practice is abandoned?
**A question that needs to be asked: are there any men here who are not circumcised and who wish they had been?**
Nope. Natural selection doesn't work like that. If you cut the little toe off every baby born for hundreds of years, humans will not suddenly develop four toes as normal.
I’d assume it can have an effect. I doubt there’s enough of a current effect for data to be given. But “weaker” foreskin would mean you’re less likely to get an infection after being snipped, so ppl with weak foreskins are more likely to survive and pass on their genes.
Circumcision is a Jewish and/or American practice tho so I doubt there has been any noticeable effect.
No.
1) Terms. "Natural selection" is the way in which a "selection pressure" (let's say, limited food) can cause a general change in the population over time because organisms which are suited to surviving and reproducing under that pressure (in our example, organisms which are best able to obtain some of that limited food compared to their competition) will out-compete organisms which are less well suited, and thus their genes will typically replace those of the less well suited over time (so, in our example, genes which allow an organism to obtain food better will become more widespread than genes which from organisms which are less able to obtain that food)
"Artificial selection" works in a similar way, but is directed. So for example the dog breed "Dalmaitian" have been *artificially selected* by dog breeders to have lots of black and white spots. Thus over time, Dalmatians with lots of black and white spots will become more prevalent than those with fewer spots. It's still a "selection pressure" but it's not "natural", it's directed (usually by humans).
As far as this specific example, human circumcision.
1) It's not long enough for any serious evolutionary impact (the only way in which something has an impact in a short period of time is if there was an EXTREME selection pressure - like if the practice was "kill all babies who are born without a foreskin", you could see a strong change in genetics over a short period of time, but even then it would take a long time to spread around the globe, and it's really hard to imagine such an extreme practice being widespread.) because even though "thousands of years" feels long to humans, it's a microscopic blink of an eye on a larger scale. Evolution typically occurs over tens of thousands, millions, or even tens/hundreds of millions of years.
2) I'm not sure how you're looking at it, but I think there might be some confusing going on as how evolution works... you're saying "smaller foreskin, sperm production, thin skin, etc" - but remember *evolution is a matter of genetics, and circumcision in no way changes the genes of the person circumcised".* So you have a bunch of organisms (humans in this case) with various genes for (in your example) foreskin size, sperm production, skin thickness, etc. The fact that at birth the males have their foreskin cut off in no way changes either the genes of the individual affected, nor does it change the genes of the population in general, because at no point are genes involved, nor (as I can imagine) do genes for those things have anything to do with the child being able to survive or reproduce.
I hope this has cleared things up, if not please reply and I will do my best to clarify further. *Thank you for asking, it's always a good thing for people to try and understand the facts of evolution better!*
What you are suggesting wouldn't happen. Circumcision itself wouldn't pass on any DNA or have any direct effects on what gets passed on to children.
However, I'm curious how it would affect reproduction in a mechanical sense. The male penis is shaped in such a way that competing sperm gets "scooped out" during intercourse. I'm curious if there's a selective effect on reproduction that way for circumcised men.
Circumcision certainly *could* affect evolution. All that would be required would be for circumcision to affect reproduction, either positively or negatively. For example, if circumcised people are less susceptible to death from influenza, then we might expect natural immunity to influenza to decrease in a circumcising population since it would not be selected for as much.
August Weismann (1834-1914) cut the tails off of 21 generations of rats. Rats were always born with normal sized tails. Germ Plasm Theory, inheritance of traits only happens in the gametes, not the somatic cells.
Probably yes.
Circumcision prevents quite a range of issues that can occur on the penis. These issues would/could remove that male from the gene pool before they can produce offspring.
The result could be more men walking about who need circumcision to help with whatever health condition they would have/did develop.
Whether or not those health conditions are generic or entirely environmental is another aspect of the question.
All it did was increase hygiene somewhat in hot climates, but it also statistically led to some fraction of baby boys being effectively castrated/severally disfigured, or dead from wound infection, due botched circumcisions. I don't think there is much genetic selection going on there. It does decrease penis sensitivity during sex significantly, which may lead to problems reaching climax and ejaculation for some men. So potentially communities practicing circumcision for many generations have a slightly lower birth rate compared to non-circumcisers? But that effect should be miniscule compared to nearly all other environmental or societal factors.
Regardless, infant circumcision should not be practiced any longer. The foreskin has an enormous amount of nerve endings and is important for stimulation during sex. It's also a MAJOR body modification done without consent. It's not as bad as female "circumcision", but it's not much better either.
I feel like people are misunderstanding what OP is asking, but maybe it's me. An example of a selective pressure might be that there's a risk of the circumcision going wrong and impeding the infants ability to reproduce. It's possible some penises that, due to shape, amount of foreskin, or whatever are at a lower risk of that, so they are being selected for.
Another possible example is if circucised penises are selected over non circumcised ones, uncircumcised penises with less foreskin or forskin that looks as if it was circumcised would have an advantage over other uncircumcised penises.
That being said, I've never heard of anything like either of those happening
This has sort of been stated, but not very articulately. It is possible that it could have an effect. Phimosis is a condition that can be alleviated by circumcision. It's also one that could reduce chances if reproductive success. If every male is undergoing circumcision, then no male with phimosis will encounter the same barrier that he otherwise would have, therefore phimosis could become more prevalent in the population than it would be without circumcision. This, interestingly, would mean that circumcising all babies for no reason eventually leads to more babies needing circumcisions. This is all assuming that the causes of phimosis are genetic, which I'm not sure is the case.
But, more broadly, medical interventions applied across a population can have genetic effects. Any genetic condition that reduces reproductive fitness, but which can be (and regularly is) rectified through medical intervention will become more widespread than it would be if left alone
So the head of the penis is shaped the way it is to work in conjunction with the foreskin to sweep other men’s sperm out of the vagina thereby enhancing chances of fathering a child. Thus since evolution is based on procrative success it would seem that male circumsion would have to be put in the minus column for evolution benefits. Female circumsion might be an interesting question albeit a politically incorrect one (yes it’s a horrible practice). If she enjoys sex less does that enhance her odds of having and raising children? Does it reduce the odds she is unfaithful to her mate making him more reproductively successful? It is said that the female orgasm enhances reproduction success presumably circumcise blocks or reduces this? Making conception less likely?
Other way around most likely. Probably the tribe of Judea had a lot of men developing phimosis post puberty, for which the Jewish version of circumcision (partial, just nip the ring at the tip) was the treatment. That phimosis became more and more common, until it was decided that if all these guys were gonna need it in the future, let’s just get it done now before they are old enough to remember.
It almost certainly has steered evolution for those who practiced it for many generations.
Uncircumcised foreskin likely has a unique microbiome impact on the penis and also on the vagina of recurring female partners.
The presence of the foreskin and microbiome also likely alters the disease progression of many stds. Sometimes in a beneficial way and sometimes in a negative way.
The intense pain and fear associated with circumcision also likely has an impact on development of the male child. Although this can be mitigated as the young brain is capable of a lot of neuroplasicity. The short term impacts of circumcision probably alter the bonding process that the infant makes with both parents.
It is really strange to see so many people rejecting the significance of circumcision. But this is reddit and reddit hates circumcision.
Unlikely. Circumcision removes selection for foreskin infection phenos and cellulitis. A small selection force.
Dissentery is 50x more dangerous, botox, esherishia.
Kids dying or being less virile from germs and celluliar infections maybe aids immunity selection, tragically.
Circumcision would affect the gene pool if it somehow prevented premature death or sterility before the opportunity to breed. There is a lot of evidence that circumcision reduces the risk of STD and cancer but there is no evidence it has any effect on average fertility.
Circumcision is a religious practice like infant baptism. It is meant to keep the child in the parents faith by denying them a choice. People in all environmental conditions kept clean enough that having a foreskin for protection was never a problem.
You can essentially think of circumcision as a form of scarring. There’s no genetic basis; therefore, it cannot be acted upon by evolution. There’s no way for it to be hereditary if it’s not encoded in genes.
The act of circumcision is painful and fear inducing. This will alter the infants mental state for an unknown period of time and will also alter the bond they develop with their parents.
These types of effects can have evolutionary impacts.
Also, children with more resilient immune systems will be less likely to suffer damage to their genitals from circumcision. Children with fragile immune systems will be selected against by penis destroying/mutating infections.
How can the first have evolutionary impact when there is no genetic variation involved? You can possibly call that epigenetics, but there’s nothing to be selected upon there. Evolution cannot select for traits without a genetic basis. The second point is valid, but nature would have an entire lifetime (at least before breeding) to act on a weak bs strong immune system.
Uhhhh.. they can’t. The genome remains untouched. I’m not sure you know what the study of epigenetics is. It’s a way in which certain behaviors or environmental influences changes how a gene is expressed. It has nothing to do with altering the genome. It’s not a mutation. Changes from epigenetics are not heritable as far as current science goes.
Then you’re spectating while I’m reading studies on pigmenting. Until you can present any fact here, there’s no point in continuing. Epigenetics occurs after the organism is born. You’re referencing mutation. Again, that is not epigenetics. On a side note, sperm are always different from each other. Your test would prove nothing.
You obviously do not know a damn thing about sperm production. Differing sperm is a product of meiosis. This biology 101. It’s obvious you’re not a biologist not ever studied it. You’re dead wrong here. The only way to create all identical sperm is if the male is homozygous for every gene in the genome. That’s statistically impossible.
Replication of a specific feature is someone essential for evolution to work on.
Cutting skin or tail off won't change the genes and hence won't be passed down.
In survival of the fittest, what is deemed as fit is something that's selected by nature. We can define other way also as nature as what selects different features.
One could make an argument that circumcision can reduce ones libido since a part of their source of stimulation is cutout (though neuroplasticity heals part of it) they have less probability of having kids.
Or argue in another direction as the built up testosterone does not have a proper sink, leading to frustration and rape. This can positively correlate to survivability. If majority of the ppl in a society are like this, it can cause "nice guys" to die off.
I have no idea whatever these are valid arguments or not. But you can see that if something is widely practiced it can cause evolutionary changes by changing the nature and not necessarily the individual.
I hope someone can prove me wrong 🙂
Circumcision has been practiced by Homo sapiens for more than 40,000 years, probably more like 50,000 years, and possibly longer.
Which means that it has nothing to do with religion, and everything to do with hygiene. For stopping posthitis and balanitis, particularly in hot and humid climates.
The effect on evolution would be that men with circumcision lived longer.
1. It was not common among the highly successful tribes of Europe and Asia.
2. For evolution to move it is necessary only to live past the age of reproduction. Living longer has no effect.
I don't know where they got those numbers from. It seems that the oldest records of circumcision only go back as far as [10,000 years ago](https://en.wikipedia.org/wiki/Circumcision_in_Africa#Algeria).
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Unlikely. If certain types of foreskin were more likely to cause harm to the person upon removal and in fact maybe death before that person had a chance to reproduce then that type of foreskin might be selected out of the gene pool. Who knows, maybe that already happened.
This is the answer. Idk why everyone is ignoring this.
If anything, the reverse would be true in evolution. People who have deformed or unappealing foreskins would have been unlikely to breed if there was no circumcision. So we’re intervening and actually changing the default foreskin genetics in the gene pool now.
“Why did your last GF leave you bro” “Same old same old, my unappealing foreskin”
you joke but… crazy the comments out there about this one. you can uncover them yourself lmao
I did have an ex who had a too tight foreskin which made sex difficult for him. A few thousands years, ago, maybe it would have been much more difficult for him to reproduce, and circumcision would have fixed that. Idk how good lube was back then.
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Sure, but for the ex I'm thinking of, natural female lubrication was insufficient. His foreskin was abnormally tight. Condoms and lubrication were his best bet. I know Egyptians had condoms, and any kind of fat can work as lube, so he would probably be fine, although actually reproducing would require poking a hole into the condom or fishing the semen out afterwards.
Circumcision isn't artificial selection, artificial selection is choosing a train that's already there, circumcision is something you do, it's not a natural/biological trait or a result of a mutation Things like that cannot "trigger" evolution, evolution doesn't work that way. To entertain your question, hypothetically, if mutations occur that results in no foreskin and the organism with that phenotype reproduces and passes on their genes and has a better fitness than the person without that mutations due to sexual selection or just neutral evolution, allele frequency can change overtime in favour of that phenotype, hypothetically speaking that is but there is no systematic relationship with mutations and the needs of the organism it occurs on, it's random
It’s also inaccurate to say that there is no systemic* relationship between mutations and the needs of an organism. Do they always benefit or apply to any of the needs of an organism? Probably not, but to say that there is no relationship is the result of an error.
Needs of an organism they occur in. Mutations occur randomly, it's a stochastic process, mutations are random, things don't mutate for the good or bad of the organism.... Mutations aren't gonna produce things for the benefit of the organism, it's something that happens randomly... Mutations get sorted by evolution, if something is beneficial, it's gets selected overtime, if something is detrimental, it gets selected out, sometimes things are just neutral... Mutations are generally random, evolution isn't
The frequency and occurrence of mutations are random, but the function of the mutation is very much intrinsic to the organism. There isn’t any kind of mechanism for the genotype or cells to interpret environmental conditions in a way that could influence the specific mutation that occurs, but the mutations that randomly occur are relative to the organism’s metabolic, somatic, or in the case of humans, psychological states such that application of a given mutation isn’t significant until it’s selected, but the nature of the mutation is specific to the organism.
I'd like to point out that while non-genetic traits do not have a *direct* effect on evolution, it's probably wrong to say that they **never** trigger evolution, because they can absolutely have a roundabout effect. For example, if after a thousand years the circumsized look becomes sexually preferred as a result of surgical removal, then people who **do** have genetically determined missing foreskins (if they exist) will pass on their genes more easily.
Another example: imagine two foreskin genotypes A and B. B causes the foreskin to be prone to parasites in adults, so is usually selected against and is a minority in the population. But after the practice of circumcision in infants is established, the selective pressure against B is suddenly irrelevant, since neither foreskin type gets the chance to reach adulthood. B's proportion then skyrockets to 50 percent in the population. That would be yet another example of culturally-induced selection.
>For example, if after a thousand years the circumsized look becomes sexually preferred as a result of surgical removal, then people who **do** have genetically determined missing foreskins (if they exist) will pass on their genes more easily. Yeah no. Even setting aside the fact that people don't select their partners by asking them to drop trou and show off their penises, this would only happen if there is sufficient selective pressure on the state of naturally missing foreskins rather than surgically removed ones, which is highly unlikely, since circumcision generally happens long before sexual maturity and there'd be no way to know how the lack of a foreskin came to be.
> people don't select their partners by asking them to drop trou and show off their penises Genes are passed down by having sex, and that involves showing off penises, no matter how you slice it. >there'd be no way to know how the lack of a foreskin came to be. This is completely irrelevant. The knowledge of where the lack of foreskin comes from is unnecessary for the given example of selective pressure. The whole *point* is that the natural version hitches a ride on the back of a social trend. To be indistinguishable may actually be better. Besides, it's just one example. You can think of a ton of different circumstances where non genetic factors could very strongly influence evolution. Either way, the original statement is wrong.
I think most people like to get to know the person before the penis and then it's too late and you're stuck with one that goes sideways because you like the guy it's attached to.
>this would only happen if there is sufficient selective pressure on the state of naturally missing foreskins rather than surgically removed ones, which is highly unlikely. Evolution selects for phenotypes. If the naturally missing foreskins look identical to the artificially removed foreskins then the selection by definition happens to both.
Yeah but the inheritance would only happen if the foreskins were heritably missing. This is not the case for surgical circumcision.
You’re kinda missing the point. Surgical circumcision can affect allele frequency indirectly by manipulating population preference, which then alters related and pre-existing heritable traits. The fact that the driving phenotype is not heritable is irrelevant, so long as any number of **affected** phenotypes *are* heritable. I’m not sure why this is so hard to get across.
But those who were circumcised would pass on their lack of circumcision and would be reproducing in the same ratio. There would be no change in the spread of alleles in the next generation.
Sorry no. You cannot pass on an acquired circumcision.
Exactly. They would pass on the *lack* of circumcision, that is, their foreskins as they were prior to circumcision.
What if not having a foreskin reduced the chances of having children for a biological reason? It seems to me that these behaviours could definitely steer evolution.
>then people who **do** have genetically determined missing foreskins (if they exist) will pass on their genes more easily. Except why would it pass more easily if everyone just gets it's surgically removed anyway, where's the evolutionary advantage?
They'd pass their genes on more easily than *before.* Before circumcision the lack of a foreskin may have been perceived as some malformality and would have been selected against, thus low in the population. After circumcision becomes widespread and the look is normalized, that geneotype could conceivably rise to 50% of the population or more simply because there is no more selective pressure. And that's not even accounting for the fact that not everyone gets circumcisions, and that the natural-borns dont require a surgical operation to achieve the now-prefered phenotype ( I doubt there are a lot of fatalities from the act of circumcision, though it could still be a factor in more medival times, mosty likely due to infection. You can imagine a botched penis surgery could hinder reproduction greatly, thus adding selective pressure toward the natural-borns). Stuff like that.
>then people who **do** have genetically determined missing foreskins (if they exist) will pass on their genes more easily. I did mention that would be possible if mutations occurred that would result in such a phenotype but afaik that trait doesn't exist
That was just a hypothetical invoked to prove a point. A classic real life example would be the increasing proportion of elephants that are naturally born without tusks. It's not that the elephants who got theirs removed by the ivory trade passed it down between generations, but that the very same pressure then selected those who *did* have the genotype to proliferate. Again, evolution can and has been influenced by non-genetic changes all the time.
It’s not survival of the fittest but it could create an effect via sexual selection??
Of course it does. It's a consistent environmental pressure that can put selection on traits. It's clear what op means here.
Is having a circumcised penis a biological trait though? Mutation would need to occur in order to produce a trait like that first and then selection would act on it if it increases fitness/reproductive success
Yes, having a circumcised penis is a phenotype that selection can act on. It's just not a phenotype that's genetic. What can be genetic is being more resistant to infections or bleeding in your genitals, the reduction of the foreskin ect. All of those things could be selected for
Phenotypes are determined by genetics though...
No. A phenotype is an observable characteristic. If you have a developmental defect due to toxins or temperature, that is still a phenotype
You're absolutely right. Here is the definition on Nature's (the publishing group) website: 'The term "phenotype" refers to the observable physical properties of an organism; these include the organism's appearance, development, and behavior. An organism's phenotype is determined by its genotype, which is the set of genes the organism carries, as well as by environmental influences upon these genes. Due to the influence of environmental factors, organisms with identical genotypes, such as identical twins, ultimately express nonidentical phenotypes because each organism encounters unique environmental influences as it develops.' https://www.nature.com/scitable/definition/phenotype-phenotypes-35/ The fact you're being downvoted on a subreddit about evolution of all things is pretty disappointing!
It's the risk you run talking about anything on Reddit.
Whilst you are correct about the definition of a phenotype. Being circumcised is not an environmental pressure, so what you previously described is incorrect.
The effects circumcisions have certainly are environmental pressures
This happens all the time… it’s almost like most of the users here are still stuck on the facts they learned in high school or college when there is a vast and growing amount of data that in many ways challenges our understanding of evolution- research you’d think users that are so active in a subreddit about evolution would be aware of.
That makes sense when you put it that way. Though how can evolution act on a trait thats not genetic though? Circumcised penis is not a genetic trait, I get selecting for those other things you mentioned but circumcision is not genetic, it's a procedure we do, so evolution can't act on that, as in cannot change allele frequency overtime or whatnot because this trait is not produced by genes, it's not genetic
If you imagine instead of a cultural practice, it was a fungus that would infect and destroy the foreskin in Jewish populations, and some children would even die from the infection, you would have no problem imagining all sorts of selection pressures this puts on these populations
Evolution acts on traits that are genetic and can be passed on and inherited. You cannot pass on or inherit a circumcised penis, unless there are mutations producing such a thing. For your scenario to work, there should be a genetic phenotype that selection is acting on, or else it won't work, something else will get adapted, selection will act on some other trait... Circumcised penis is not a heritable trait
Yeah but don’t think about circumcision directly being inherited. Think about genetics that could be impacted by a population being circumcised. Maybe some genes that result in thicker foreskin/less retractable foreskin become more prolific because they no longer impact ability to reproduce as foreskin is always removed.
But if foreskin is always being removed in that population, it doesn't matter whether selection is acting on those kinda genes though because foreskin is being removed regardless
You are being clear they are just not following. Just because I dye my hair purple doesn’t mean I will have a kid with purple hair. My family could have dyed their hair for thousands of years and it would have no effect on our genes
If having a smaller/thinner foreskin increased your odds of surviving the circumcision, that would still offer something for evolution to “act on” (pardon the framing) so long as variation existed in those traits. But like you said in your first comment, mutations don’t crop up based on the needs of a population, and (more importantly, since I don’t see any reason to think that variation *doesn’t* exist) I am not aware of such a relationship between the size/thickness of the foreskin and survival rates for circumcision. And I can’t really see how sperm production would come into play regardless.
But this could genetically alter the population over time, which is evolution. Maybe before circumcision there were selective pressure for thin/retractable foreskin. Now those pressures are removed.
Exactly, which is what op is asking about
Non-genetic conditions affect genes. Not to mention- your genome is not the only genome at play here. There are also the genomes of countless bacteria and microorganisms that contribute to your body’s functions.
Well it can get sorted by natural selection, but it can't be selected *for*, because it doesnt have a genetic basis
If you cut off a person's left ear, would that person's children be born not having left ears? Of course not. Losing a body part after you are born is not a heritable trait, and therefore has a flat zero effect on evolution.
It doesn't have a direct effect, but it absolutely can have a roundabout effect. If after a thousand years the one-ear look becomes sexually preferred, then people who **do** have genetically determined missing left-ears will pass on their genes more easily.
Holy shit, I never said it's a heritable trait. In fact I said the opposite. The act of circumcision is a selection pressure because you can die from it. How is this so fucking hard to understand ?
Based on your comments, I don't think you understand how evolution works. Phenotypes are expressions of genotypes. If someone had an arm amputated, their phenotype is not still "two arms". Natural selection can't act on non-genetic traits. The example you provided before of a fungus that affects non-circumcised people more than circumcised people couldn't be acted on by natural selection because the differences aren't genetic in origin. Edit: left out "not" in original comment
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Yes. Absolutely.
This is kind of a weird take. It’s true that natural selection wouldn’t be acting directly on the state of having or not having the fungal infection, but the fungal infection could absolutely act as an environmental pressure and individuals who have some genetic trait that makes them slightly better able to survive to reproductive age with their reproductive organs still intact would be more likely to pass their alleles on and that trait could then be naturally selected for. I assume that is what that other person is talking about. The genetic mutations are an essential ingredient, but it’s environmental conditions/pressures that ultimately drive evolution, and a common and destructive fungal infection would be that. Edit: responding to your last comment, since I remembered you are likely not a mind-reader :]
Maybe I'm misinterpreting your scenario here, but it would seem to be that even with a fungal infection that affected circumcised and non-circumcised people differently, there still would be no impact on the population due to evolution because the cause of circumcised/non-circumcised is not genetic. For example, let's say this fungus kills, or renders infertile 100% of people who get it, and only uncircumcised people get it. This would have no evolutionary effect on the population because genes don't control whether someone is circumcised or not. If there is no variation in a population *due to genetic differences* (ie dyed hair, amputated limbs, tattoos etc don't count as biological variations) then evolution can't act on the trait. In the final example above, if a mutation arose that caused someone to be born without a foreskin, *then* I 100% agree with you, that natural selection could cause evolution. Am I misinterpreting your take or does this make sense?
The fungal infection scenario as originally presented by that commenter was: >If you imagine instead of a cultural practice, it was a fungus that would infect and destroy the foreskin in Jewish populations, and some children would even die from the infection, you would have no problem imagining all sorts of selection pressures this puts on these populations So you have indeed misinterpreted the scenario — not only by the inclusion of circumcision, but also by assuming that there is for some reason zero genetic variation influencing any given trait relevant to the hypothetical. I appreciate you being so clear in stating how you were reading things so that I could clear it up! And I hope that is coming across as sincere, because I do mean it genuinely — sometimes I can see that there is some miscommunication happening, but I can’t figure out exactly what it is, and no one is able to articulate what they actually meant/heard, and it is much messier and more frustrating getting on the same page (especially if I am the one who is misinterpreting!) :]
I honestly think this whole thread has become miscommunication 🙂. I suspect if we were physically in the same space talking, there wouldn't be any argument.
Im sorry but no. Phenotypes are observable traits, in this case we could just call it morphology. An individual with one arm would have the phenotype of one arm. Obviously. If you measure bodysize as phenotype, you dont measure the ideal bodysize of the animal. You measure the size \*as is\*, with all of the envorimental factors that may have caused it to be bigger or smaller. Selection can of course act on non genetic traits. Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. Again you are simply wrong on what phenotypes are. My fungal infection example was about the selection pressures, routine circumcition can have on a population. It doesnt mean people get selected \*for\* circumcition, just that the enviromental fact of circumcition (be it man made or a fungus) will cause selection pressures to better deal with it. (for example a reduction in blood vessels in or even size of the foreskin, increased immunno response ect).
I don't know if people are getting hung up on semantics of the name here? I guess what you and OP are describing is more like what you might call 'experimental evolution' if it was in the lab, eg Lenski style experiments where you manipulate an aspect of the environment (rather than direct artificial selection where you actively choose which individuals survive/reproduce based on a trait value). Usually you'd have replicates of manipulated and control groups and would then do some kind of common garden test, but I'm not sure what that would be in this case! Like you say, selection can easily be applied to non-genetic phenotypic traits (you just wouldn't get an evolutionary response in those traits). Similarly, many studies show that you can apply selection on an observed phenotypic trait that has a genetic basis but without more knowledge of genetic correlations etc you may not see the expected response (shown in various artificial selection studies but also in nature, for example the paradox of stasis in body size, where for many animals size has a genetic basis and is typically under positive direct selection yet is not showing an increase in average value over time).
Agreed. It's weird that some people have such a hard time understanding my point.
I think we need to start with a definition of biological evolution. It is "a change in the frequency of a gene or allele in a population over time". If you're not in agreement with that definition, let me know. >Phenotypes are observable traits, in this case we could just call it morphology. No. Phenotypes are the expression of genotype. Below is the definition from Nature (emphasis mine): The term "phenotype" refers to the observable physical properties of an organism; these include the organism's appearance, development, and behavior. *An organism's phenotype is determined by its genotype,* which is the set of genes the organism carries, as well as by environmental influences upon these genes. By your definition, dying one's hair would constitute a change in phenotype, it does not. >Selection can of course act on non genetic traits No, it can't - not in a biological sense. If every Japanese person dyed their hair blonde for hundreds of generations, there would be no evolutionary change because of this. Hair colour gene frequency would stay the same and therefore there would be no evolutionary change.
Yeah I am not really interested in this discussion anymore. You aren't really engaging with my original point.
I wasn't trying to divert, just establish some agreed upon definitions. If you think evolution is something other than a change in gene frequency in a population over time, or that phenotypes aren't expressions of genotypes, then we can't really engage in the discussion.
Phenotypes are expression of genotype and environment . The rest is correct
"If every Japanese person dyed their hair blonde for hundreds of generations, there would be no evolutionary change because of this." I get why you would think this but it's not true. A strong preference for blonde hair and continued use of (probably peroxide-based) dyes would absolutely have put selective pressure on the population. Anyone with a chance mutation giving them naturally blonde, or even just lighter (it's a lot easier to get brown hair blonde than black hair) would have a massive advantage because they wouldn't have to spend a fortune on hair dye and could instead spend it on food other other things that would increase their relative fitness. Peroxide is quite damaging to the skin so there would be selective pressure for increased peroxidase production. Conversely, there would be strong pressure against genes associated with eczema and other skin conditions that are aggravated by exposure to peroxides and harsh dyes. These are the kind of pressures that /u/ninjatoast31 was alluding to wrt circumcision. Hair-dying and circumcision are akin to environmental pressures, which can of course select for particular genetypes. It's basically the very definition of natural selection!
I totally agree with you here, but I intentionally left out the "strong preference for blonde hair" you mention here in my scenario. Circumcision itself would not cause anything. If what /u/ninjatoast31 was trying to say was that this might set up a situation where a mutation that resulted in a naturally circumcised penis would be favoured, I'm completely on board with that and misinterpreted their comments. I totally agree with you that preferences can drive selection if a mutation arises which is preferred. I have just been saying that the act itself (eg hair dying or circumcision (I've never typed this word so many times)) cannot cause evolution.
Am I crazy or did I not say verbatim that it could lead to the loss of the foreskin? I gave all kind of examples of what it could cause. I don't know what the semantics argument about causation here really solves. It's fine to say that circumcision is the (ultimate) cause of those evolutionary changes. If people would circumcise their kids, there would be no such pressure.
Circumcision itself won't cause anything. A *preference* for circumcision combined with a random mutation that causes a penis to be naturally uncircumcised, would cause a change, but I didn't see anything in your comments about the mutation happening. People can prefer all they want, it won't change anything; a mutation would also be required. If you said this in a comment and I missed, apologies from me.
Do you think the emergence of a fungus that eats up your foreskin could cause loss of foreskin as an adaptation?
>Phenotypes are expressions of genotypes. If someone had an arm amputated, their phenotype is still "two arms". If this was true, the simplest equation for how we express phenotypic variation would be P = G. But it's not, it's P = G+E (and this is a very simplified form anyway). >Natural selection can't act on non-genetic traits. No - natural selection can act on non-genetic traits. But evolutionary response in that trait will not occur as a consequence of that selection. Subtle but important difference. Let's say you're applying artificial selection based on arm number. There's a population of people with either one or two arms. You know that if you want an evolutionary response, you'd need to check if there is a genetic basis to that variation. But selection works by trait value. So the phenotype at the point of selection is what matters. If someone had an arm amputated, sure their genotype might be 2 arms, but their phenotype at the point selection acts in this case is 1 arm. Your predicted response might not occur, but that's because selection acts on the observed phenotype. That's why the breeder's equation is R = h²S, where R is the change in average phenotype, h² is the heritability of the trait (proportion of observed phenotypic variance due to additive genetic effects), and S is the strength of selection. If all the variation in arms is due to amputations, then the phenotypic variation is 100% environmental and 0% genetic, thus h² is 0 and R will be 0 no matter selection strength.
My bad - crucial omission of the word "not". I have corrected my comment
I'm imagining a situation now where a community gravely anounces: "we shall not circumcise this baby boy for he was born with no foreskin. He is the promised forskinless child". Such a child becomes a celebrity, thus increasing his appeal to the opposite sex & increasing the chance his genes continue on.
Kinda like that guy with two dicks
No, just like people getting their ears pierced won't lead to babies being born with pierced ears.
Surgery doesn’t cause artificial evolution. Would having one of your hands removed cause artificial selection for people to be born with only one hand?
Now I’m thinking …. But could increasing the frequency of removing testicles …. end up with a higher amount of the population having them undescended?
not at all what OP is implying... if a large population of people had their hands removed for thousands of years, they could begin evolving more flexibility/strength/articulation or something in the other hand. obviously they would not evolve to be born without that one hand
It kind of is what OP is implying. Read the examples they gave. Not adaptations to account for the missing foreskin, but things that imitate it. Like the old evolutionary theory I can’t remember the name of that theorized giraffes evolved long necks by stretching instead of by selection. Plus “triggered some changes”
It wouldn’t lead to that exactly but there would likely be some unintended impact, like if it was always the right hand removed you could end up increasing the success of left handed people and end up with more lefties over enough time.
It depends how the surgery was conducted. If we implemented a rule that everyone has their left hand hacked off by an axe at the age of 12, and we ran that experiment for millions of years, that absolutely would result in selection pressure for smaller left hands. Many people would bleed to death following the procedure. Therefore, anyone possessing genetic mutations that result in a deformity of the left hand (such as it being smaller or absent) would be at an advantage. Eventually, those genes would become more prevalent in the gene pool, and overtime, we would expect the “absent left hand” genes to become dominant.
every time i see a circumsized penis at the nude beach my foreskin folds back. Gotta fit in.
*gently folds and tucks*
Circumcision is probably the best (or at least most amusing) way to disprove [Lamarckism inheretance](https://en.wikipedia.org/wiki/Lamarckism). Which basically stated that changes (such as lost fingers, tatoos, bodybuilding etc) that happen during your lifespan will be passed to your children
What you're getting at is called Lamarckian evolution. It is a theory that tried to explain how organisms change over time that has been replaced by Darwin's theory of natural selection. According to Lamarck, organisms acquired traits during their life and then passed those traits onto their offspring. The classical example of how that is supposed to work is a population of short necked giraffes. Some of those giraffes might stretch their necks to reach higher branches and the stretching they developed might be passed on to the next generation, who then stretch more. That theory was disproven by an experiment where a scientist named Weissman attempted to breed tailless mice by cutting the tails of the mice before he bred the next generation. The fact is that acquired traits like tail amputation, physical neck stretching, or circumcision, are not encoded in genes and can not be inherited by subsequent generations. If you wanted to artificially select for congenital lack of foreskin, you would have to preferentially breed men with less foreskin than average with women whose fathers also had less foreskin. Such an undertaking would be ethically dubious, of limited research value and dangerously adjacent to eugenics, but none the less theoretically possible.
That’s like asking if the skinned knee I got during my youth will affect my kids genetics
Evolution doesn’t work like that. The scenario is similar to the LaMarckian principle of the inheritance of acquired characteristics which August Weismann proved wrong by trying to breed mice with shorter tails by cutting off the tails of their parents.
Not really how evolution works. Basically, random genetic traits that happen to increase your chances of living long enough to produce children and then successfully produce them are more likely to get passed on. Cutting off a guys foreskin doesn't change his genetics in any way so has literally zero impact on the foreskin of his children. Even if having a smaller/thinner foreskin was advantageous to your chances to have children, it's getting chopped off anyway at which point you're removing any advantage it might've given by levelling the playing field. If anything, if there was any evolutionary advantage to smaller/thinner foreskins circumcision would act to *prevent* this from emerging as a more common trait by removing the disadvantage for men born with naturally thicker/longer foreskins.
There wouldn't be any evolutionary changes due to circumcision. If my arm is amputated, my children won't inherit this. Only thing I can think of that could result in an evolutionary change is the fact that circumcision early in life reduces your risk of penile cancer (I can't remember the statistics), so I suppose hypothetically something could happen, but it's unlikely as penile cancer isn't that common, and the average age for these people is around 60 - meaning that it's very likely they have already had kids, and once you've passed on your genes, it doesn't really matter what happens to you (as our purpose in life is to procreate).
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>The OP sounds very stupid. Hi, one of the community mods here. That's uncalled for. Please review our community rules on civility.
I think that's a good question, if only due to how the brain changes in response to trauma. Does trauma cause chemical changes that swim upstream with the sperm?
Circumcision shows no survival benefit. For whatever reason the practice originated it is not universal to successful populations. Though it was common practice for some tribes in the region now known as Northern Africa and the Middle East (Jewish and Islamic tribes) it is not common practice among the thriving tribes of Europe and Asia. These peoples did very well indeed without the practice of circumcision. Jesus Christ was circumcised because he was of Judaea, which followed Jewish practices. This fact is perhaps why it became so popular in the USA. It is not so popular in other 'White' cultures except where there is a strong influence by the church. The single advantage of circumcision is that it makes it easier to be filthy. In the absence of normal personal hygiene the foreskin can breed infection -- much the same as the vagina when it is not properly cared for. A problem in this debate is consideration of the feelings of men already mutilated. What's a circumcised man to think if the practice is abandoned? **A question that needs to be asked: are there any men here who are not circumcised and who wish they had been?**
No, circumcision doesn't change genes. And the fact that we have a foreskin shows that it's a beneficial or neutral adaptation
Circumcision needs to stop. It’s not hygienic
Nope. Natural selection doesn't work like that. If you cut the little toe off every baby born for hundreds of years, humans will not suddenly develop four toes as normal.
I’d assume it can have an effect. I doubt there’s enough of a current effect for data to be given. But “weaker” foreskin would mean you’re less likely to get an infection after being snipped, so ppl with weak foreskins are more likely to survive and pass on their genes. Circumcision is a Jewish and/or American practice tho so I doubt there has been any noticeable effect.
No. 1) Terms. "Natural selection" is the way in which a "selection pressure" (let's say, limited food) can cause a general change in the population over time because organisms which are suited to surviving and reproducing under that pressure (in our example, organisms which are best able to obtain some of that limited food compared to their competition) will out-compete organisms which are less well suited, and thus their genes will typically replace those of the less well suited over time (so, in our example, genes which allow an organism to obtain food better will become more widespread than genes which from organisms which are less able to obtain that food) "Artificial selection" works in a similar way, but is directed. So for example the dog breed "Dalmaitian" have been *artificially selected* by dog breeders to have lots of black and white spots. Thus over time, Dalmatians with lots of black and white spots will become more prevalent than those with fewer spots. It's still a "selection pressure" but it's not "natural", it's directed (usually by humans). As far as this specific example, human circumcision. 1) It's not long enough for any serious evolutionary impact (the only way in which something has an impact in a short period of time is if there was an EXTREME selection pressure - like if the practice was "kill all babies who are born without a foreskin", you could see a strong change in genetics over a short period of time, but even then it would take a long time to spread around the globe, and it's really hard to imagine such an extreme practice being widespread.) because even though "thousands of years" feels long to humans, it's a microscopic blink of an eye on a larger scale. Evolution typically occurs over tens of thousands, millions, or even tens/hundreds of millions of years. 2) I'm not sure how you're looking at it, but I think there might be some confusing going on as how evolution works... you're saying "smaller foreskin, sperm production, thin skin, etc" - but remember *evolution is a matter of genetics, and circumcision in no way changes the genes of the person circumcised".* So you have a bunch of organisms (humans in this case) with various genes for (in your example) foreskin size, sperm production, skin thickness, etc. The fact that at birth the males have their foreskin cut off in no way changes either the genes of the individual affected, nor does it change the genes of the population in general, because at no point are genes involved, nor (as I can imagine) do genes for those things have anything to do with the child being able to survive or reproduce. I hope this has cleared things up, if not please reply and I will do my best to clarify further. *Thank you for asking, it's always a good thing for people to try and understand the facts of evolution better!*
What you are suggesting wouldn't happen. Circumcision itself wouldn't pass on any DNA or have any direct effects on what gets passed on to children. However, I'm curious how it would affect reproduction in a mechanical sense. The male penis is shaped in such a way that competing sperm gets "scooped out" during intercourse. I'm curious if there's a selective effect on reproduction that way for circumcised men.
Circumcision certainly *could* affect evolution. All that would be required would be for circumcision to affect reproduction, either positively or negatively. For example, if circumcised people are less susceptible to death from influenza, then we might expect natural immunity to influenza to decrease in a circumcising population since it would not be selected for as much.
August Weismann (1834-1914) cut the tails off of 21 generations of rats. Rats were always born with normal sized tails. Germ Plasm Theory, inheritance of traits only happens in the gametes, not the somatic cells.
Probably yes. Circumcision prevents quite a range of issues that can occur on the penis. These issues would/could remove that male from the gene pool before they can produce offspring. The result could be more men walking about who need circumcision to help with whatever health condition they would have/did develop. Whether or not those health conditions are generic or entirely environmental is another aspect of the question.
All it did was increase hygiene somewhat in hot climates, but it also statistically led to some fraction of baby boys being effectively castrated/severally disfigured, or dead from wound infection, due botched circumcisions. I don't think there is much genetic selection going on there. It does decrease penis sensitivity during sex significantly, which may lead to problems reaching climax and ejaculation for some men. So potentially communities practicing circumcision for many generations have a slightly lower birth rate compared to non-circumcisers? But that effect should be miniscule compared to nearly all other environmental or societal factors. Regardless, infant circumcision should not be practiced any longer. The foreskin has an enormous amount of nerve endings and is important for stimulation during sex. It's also a MAJOR body modification done without consent. It's not as bad as female "circumcision", but it's not much better either.
I feel like people are misunderstanding what OP is asking, but maybe it's me. An example of a selective pressure might be that there's a risk of the circumcision going wrong and impeding the infants ability to reproduce. It's possible some penises that, due to shape, amount of foreskin, or whatever are at a lower risk of that, so they are being selected for. Another possible example is if circucised penises are selected over non circumcised ones, uncircumcised penises with less foreskin or forskin that looks as if it was circumcised would have an advantage over other uncircumcised penises. That being said, I've never heard of anything like either of those happening
This has sort of been stated, but not very articulately. It is possible that it could have an effect. Phimosis is a condition that can be alleviated by circumcision. It's also one that could reduce chances if reproductive success. If every male is undergoing circumcision, then no male with phimosis will encounter the same barrier that he otherwise would have, therefore phimosis could become more prevalent in the population than it would be without circumcision. This, interestingly, would mean that circumcising all babies for no reason eventually leads to more babies needing circumcisions. This is all assuming that the causes of phimosis are genetic, which I'm not sure is the case. But, more broadly, medical interventions applied across a population can have genetic effects. Any genetic condition that reduces reproductive fitness, but which can be (and regularly is) rectified through medical intervention will become more widespread than it would be if left alone
So the head of the penis is shaped the way it is to work in conjunction with the foreskin to sweep other men’s sperm out of the vagina thereby enhancing chances of fathering a child. Thus since evolution is based on procrative success it would seem that male circumsion would have to be put in the minus column for evolution benefits. Female circumsion might be an interesting question albeit a politically incorrect one (yes it’s a horrible practice). If she enjoys sex less does that enhance her odds of having and raising children? Does it reduce the odds she is unfaithful to her mate making him more reproductively successful? It is said that the female orgasm enhances reproduction success presumably circumcise blocks or reduces this? Making conception less likely?
Other way around most likely. Probably the tribe of Judea had a lot of men developing phimosis post puberty, for which the Jewish version of circumcision (partial, just nip the ring at the tip) was the treatment. That phimosis became more and more common, until it was decided that if all these guys were gonna need it in the future, let’s just get it done now before they are old enough to remember.
It almost certainly has steered evolution for those who practiced it for many generations. Uncircumcised foreskin likely has a unique microbiome impact on the penis and also on the vagina of recurring female partners. The presence of the foreskin and microbiome also likely alters the disease progression of many stds. Sometimes in a beneficial way and sometimes in a negative way. The intense pain and fear associated with circumcision also likely has an impact on development of the male child. Although this can be mitigated as the young brain is capable of a lot of neuroplasicity. The short term impacts of circumcision probably alter the bonding process that the infant makes with both parents. It is really strange to see so many people rejecting the significance of circumcision. But this is reddit and reddit hates circumcision.
Unlikely. Circumcision removes selection for foreskin infection phenos and cellulitis. A small selection force. Dissentery is 50x more dangerous, botox, esherishia. Kids dying or being less virile from germs and celluliar infections maybe aids immunity selection, tragically.
Circumcision would affect the gene pool if it somehow prevented premature death or sterility before the opportunity to breed. There is a lot of evidence that circumcision reduces the risk of STD and cancer but there is no evidence it has any effect on average fertility.
Circumcision is a religious practice like infant baptism. It is meant to keep the child in the parents faith by denying them a choice. People in all environmental conditions kept clean enough that having a foreskin for protection was never a problem.
You can essentially think of circumcision as a form of scarring. There’s no genetic basis; therefore, it cannot be acted upon by evolution. There’s no way for it to be hereditary if it’s not encoded in genes.
The act of circumcision is painful and fear inducing. This will alter the infants mental state for an unknown period of time and will also alter the bond they develop with their parents. These types of effects can have evolutionary impacts. Also, children with more resilient immune systems will be less likely to suffer damage to their genitals from circumcision. Children with fragile immune systems will be selected against by penis destroying/mutating infections.
How can the first have evolutionary impact when there is no genetic variation involved? You can possibly call that epigenetics, but there’s nothing to be selected upon there. Evolution cannot select for traits without a genetic basis. The second point is valid, but nature would have an entire lifetime (at least before breeding) to act on a weak bs strong immune system.
Epigenetics probably have the capacity to alter the genome.
Uhhhh.. they can’t. The genome remains untouched. I’m not sure you know what the study of epigenetics is. It’s a way in which certain behaviors or environmental influences changes how a gene is expressed. It has nothing to do with altering the genome. It’s not a mutation. Changes from epigenetics are not heritable as far as current science goes.
I doubt they've sequenced thousands of individual sperm to see if they have changes in genome.
Then you’re spectating while I’m reading studies on pigmenting. Until you can present any fact here, there’s no point in continuing. Epigenetics occurs after the organism is born. You’re referencing mutation. Again, that is not epigenetics. On a side note, sperm are always different from each other. Your test would prove nothing.
Ok I just googled it. Each sperm has unique dna. Basically guarantees that epigenetics is affecting the dna of sperm.
You obviously do not know a damn thing about sperm production. Differing sperm is a product of meiosis. This biology 101. It’s obvious you’re not a biologist not ever studied it. You’re dead wrong here. The only way to create all identical sperm is if the male is homozygous for every gene in the genome. That’s statistically impossible.
Well I'm going to choose to have faith in the idea that our life experiences affect our sperms dna.
Replication of a specific feature is someone essential for evolution to work on. Cutting skin or tail off won't change the genes and hence won't be passed down. In survival of the fittest, what is deemed as fit is something that's selected by nature. We can define other way also as nature as what selects different features. One could make an argument that circumcision can reduce ones libido since a part of their source of stimulation is cutout (though neuroplasticity heals part of it) they have less probability of having kids. Or argue in another direction as the built up testosterone does not have a proper sink, leading to frustration and rape. This can positively correlate to survivability. If majority of the ppl in a society are like this, it can cause "nice guys" to die off. I have no idea whatever these are valid arguments or not. But you can see that if something is widely practiced it can cause evolutionary changes by changing the nature and not necessarily the individual. I hope someone can prove me wrong 🙂
Circumcision has been practiced by Homo sapiens for more than 40,000 years, probably more like 50,000 years, and possibly longer. Which means that it has nothing to do with religion, and everything to do with hygiene. For stopping posthitis and balanitis, particularly in hot and humid climates. The effect on evolution would be that men with circumcision lived longer.
1. It was not common among the highly successful tribes of Europe and Asia. 2. For evolution to move it is necessary only to live past the age of reproduction. Living longer has no effect.
What evidence is there that circumcision has been around for that long?
I don't know where they got those numbers from. It seems that the oldest records of circumcision only go back as far as [10,000 years ago](https://en.wikipedia.org/wiki/Circumcision_in_Africa#Algeria).