Trait changes in a species.

I was at the St. Louis Zoo last weekend checking out the chimps and got to see the hairless one again. http://www.stlzoo.org/yourvisit/thingstoseeanddo/...
{Shortened display form of URL, to restore page width to normal. - Adminnemooseus}Now, this chimp is hairless from the disease alopecia universalis(says the website), not a genetic mutation. But I would still like to discuss how major changes occur in a species. I would like to discuss how a population of hairless chimps could come about. I’ll explain how I think it could happen and I would like people to help me by pointing out my errors or adding new information.In order for this hairless trait to occur in many chimps, it would have to be a result of a genetic mutation. And this mutation would have to dominate the hair gene, and be passed on to offspring, of which some would be hairless and some would not. Then we could get a few hairless chimps that could breed and make more hairless chimps. If the environment allowed these chimps to survive, we could have a population of a species in which some had hair and some didn’t. To make a transition to a hairless species, the environment would have to be more favorable for chimps without hair, perhaps deadly for chimps with hair. Or, there could be sexual selection involved in which hairless chimps were preferred mates. After many generation of selection, the population could move to totally hairless.Make sense?This message has been edited by Adminnemooseus, 06-05-2005 03:09 PM

Thread moved here from the Proposed New Topics forum.This thread was missed; sorry it took so long to promote. Gentle and helpful responses please.This message has been edited by AdminSylas, 05-26-2005 08:07 AM

Totally. The other possibility is that one trait or other might be lost, even if they have no effect on fitness, simply by genetic drift. The fixation of a trait, especially in a small population, doesn't neccessarily imply any selective pressure is active.TTFN,WK

So you're saying that the hairful trait could be lost "simply by genetic drift" resulting in a population of hairless individuals?I thought genetic drift affects allele frequencies, but doesn't change any traits of a species without environmental pressure. Yes, it seems that the fixation of a trait is the default. RM and NS do the changing and without them there is none (besides the change in allele frequencies from genetic drift).

So, I feel comfortable with my understanding of the changes of traits in species(even though there was only one reply), but I don't know how humans became hailess. I've read the Aquatic Ape Theory but it seems very speculative.Are humans the only hairless apes?
Is there any fossil record of non-human hairless apes?
Did we become human before we became hailess, or visa versa? (possibly poor wording)
Or did we become hairless during the transition to modern human?
What does the TOE suggest about such a transition?please respond

What makes you think we're hairless? Humans (yes, even women - take a good close look if one will let you) have just as many hair follicles as the rest of the primates; its just that the hairs that grow out of them are finer and lighter.I don't know what would be in the fossil record, body parts like hair don't really fossilize.

The opposite. It is random loss / fixation of genes due to the simple fact that not all individuals reproduce successfully in a population. It is a 'pure chance' phenomenon that becomes increasingly important in small populations. No selection of any sort is required. Only if that trait is either beneficial under selection, or neutral without it, relative to the alternative allele. In larger populations, random loss of one or the other allele will be far less probable unless slection is involved, but will still occur at some loci over long periods of reproductive isolation.This message has been edited by EZscience, 05-26-2005 08:25 PM

see the {Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution} thread
EvC Forum: Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolutionthere is also one problem with apes just becoming hairless (and I'm curious how the zoo specimen gets around this): heat control. hair helps keep a mammal from getting too hot or too cold (it 'buffers' the temperatures) and so there must be some mechanism to take care of that.{{added by 2nd edit: she is kept in a temperature controled invironment}}there is also a "running ape" theory that attempts to explain the finer hair on humans, but it has some sever problems (this was discussed in the {evolution of clothes} thread - now closed){{added by 1st edit}}May I suggest you keep this topic to more {general\genertic} trait changes and pursue the 'hairless' question on the existing thread?This message has been edited by RAZD, 05*26*2005 09:29 PMThis message has been edited by RAZD, 05*26*2005 09:49 PM

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we are limited in our ability to understand
by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}

RazD and myself have already had an extensive discussion here on the evolution of hairlessness in humans, that happens to be particularly exaggerated in women. It leads to the conclusion that forces of sexual selection, rather than natural selection, are strongly implicated, in particular reciprocal mate choice where both females and males gain reproductive success by choosing mates on the basis of specific criteria. A model demonstrating this was mathematically feasible (at least for female choice) was formulated by Fisher in 1938. It shows that intersexual selection can exaggerate traits beyond the boundaries determined by natural selection alone.Bottom line is this:
You can gain fitness by being hairless if this feature renders you preferential access to high quality mates, PROVIDED the survival costs (imposed by natural selection) are not too high.Damn you Razd ! - you posted five seconds ahead of me ! This message has been edited by EZscience, 05-26-2005 08:45 PM

Yes, and it looks like a good time to move to the next issue on that thread: thermal regulation. Hope I have time this weekend to put it together.{{you snooze you loose?}} LOLThis message has been edited by RAZD, 05*26*2005 09:48 PM

deletedThis message has been edited by RAZD, 05*26*2005 09:56 PM

Cashfrog:Once again you seem to miss the whole point of the post and choose to just pick apart the mistakes someone has made in the way they express the idea. You’ll remain ignored.EZ:I don’t understand this one either. which to me would be: genetic drift does change some traits of a species.But you follow with: ‘It is random loss / fixation of genes because not all individuals reproduce successfully in a population. It is a 'pure chance' phenomenon that becomes increasingly important in small populations. No selection of any sort is required.’Is this with respect to hairlessness? I don’t think ‘pure chance’ could be the result. Some sort of pressure seems to be requires be it environmental or sexual.And: To which you replied: right after you just said: Maybe I’m reading you wrong or maybe I’m stupid but I just couldn’t make sense of that post.RAZD and EX:Thanks for the links, looks like I’ll have some reading up to do. But these threads seem to deal with hairlessness after humans already exist.Is it assumed that we only became hairless after we became human?
(probably could be worded better but I hope you understand the question)Are there any non-human hairless apes that have existed?

Lets try and sort this out.In reply to my post you said... You are completely right here, drift doesn't change the traits at all. It does however change their frequency and it can do so to the extent that the frequency of a trait becomes 0 and is lost from the population. It cannot introduce novel variation but it can remove variation from a population. Not if you accept that drift can fix alleles regardless of fitness, which it can. Drift would also work against the hairless trait when it was at low frequency however so you could argue that some positive selection would be needed to allow the trait to reach a reasonable frequency in the first place. It depends to a large extent on the size of population at the time the trait arose.It has also been suggested that hairloss would be beneficial in avoiding ectoparasites.I don't think there are any currently extant hairless apes other than man, and as Crashfrog pointed out we have no fossil record of how hairy the various fossil species of Homo are.TTFN,WK

see http://EvC Forum: Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution -->EvC Forum: Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolutionthis is part of my next installment on that thread (maybe this weekend)

You made critical errors in how you chose to frame the question. If you can't be bothered to truly understand what you're asking, how will you hope to understand the answer?I'm sorry that you'd prefer to remain ignorant; I'll continue to point out your errors whenever you make them.