Re: Anyone disagree that body hair has sensory function?
This reminds of a time when a friend of mine who is mexican had a premature baby. When I went to see her at her home and saw the baby for the first time. My first reaction was this was a baby monkey because her baby had so much dark hair over the entire body that it resembled fur.
Of course, as the baby grew it lost its appearance of being furry and looks human now. This provided strong evidence to me of our ancestrial background of once being apes.
Lol, that very nearly sounded racist. That aside, I'll nitpick - technically we not only were we apes, we still are. Scratch that, technically not only were we monkeys, we still are (apes being a type of monkey).
But, and here's the key, we weren't ever chimps, or gorillas, or any other extant species of monkey or ape. We had an "ape-like" ancestor related to modern-days apes and monkeys (albeit it on reasonably distant branches). You probably knew that, but it pays to be sure.
At one point, I'm sure we were very, very hairy. I don't think it's been fur for a while, but we gradually lost that hair. We probably didn't need it. In the future, it's possible we'll evolve away from body-hair entirely if the overall consensus of our species is that hairless is prettier. If not, we won't. Hair being useless for maintaining body-temperature or keeping the sun off our heads doesn't automatically mean it's no longer useful and all our kids will be bald...and that's not how something which once had a function becomes superfluous to find itself no longer positively selected for.
If it doesn't do anything useful (or not so useful) it will no longer be selected for by natural selection, and in that case can change and morph rather freely, until it becomes something else (through many, many steps) or ceases to occur but for random chance (like whale legs).
Greyseal, you said "I don't think it's been fur for a while, but we gradually lost that hair. " I'm curious to know why you think it would have been gradual
I'm sorry, I should make it clear when I'm talking about an individual (and an individual mutation) and a population.
The reason I think it's gradual is because we all are relatively hairless, and modern-day apes are not. As far as I know, our joint ancestor several million years ago was more like the ape - quite probably very hairy.
Unless you think at, say, 5 million BCE there was a sudden rash of bald ape babies, then we have to assume that whatever happened, instantaneous hairloss in one generation in all members of the relevant population wasn't one of them.
You could be right though, and it suddenly appeared and very rapidly speaking became the norm for some reason - I don't know - but it seems unlikely. Most change is gradual, as large amounts of change tend to get selected against whether it's a good thing or not as the single offspring in question with it would probably be less desirable as a mate.
Greyseal, I think that, if a single furless mutant successfully reproduces and has furless descendents the trait could be established within a sub-group.
You don't get a sub-group of one. You don't get a breeding subgroup from one family...or if you do it'll probably die out from genetic disease, or just plain interbreeding.
It doesn't have to have provided any net benefit and could even have been an initial disadvantage, so long as it was not so disadvantageous that it prevented reproductive success. Of course if it did confer advantage that makes it more likely they would demonstrate fitness (as in fitness = reproductive success). I don't see why it takes more than one to start things off; the question then becomes why the fully furred lines failed whilst the furless ones succeeded.
yes. You got it.
Now, you're suggesting that this "non-hairy" mutation was large and that it occured in one generation in one specimen and was dominant. You're contesting it didn't happen again directly, but that it didn't need to as because it was dominant, all offspring had it, and slowly but surely there were more of these hairless monkeys until they could divide into a subgroup.
You could be correct, but you're probably wrong for a number of reasons
1) changes that large don't, afaik, usually occur 2) the trait you're talking about would probably not be quite so dominant even if it did happen 3) and once again, you don't get a population of one, and you don't get a breeding population of one family 4) so what you might get is hairless mutants popping up with increasing regularity until it "bred true"
this fits my description of "slowly" and "gradually", even if the mutation itself was sudden. I should have been more specific.
I don't believe in your "sudden in one generation from hairy to hairless ape" for a number of reasons, and I'm certainly not expert enough to say if we have the proof you're wrong - somebody here might, or of course I could google it and see.
Greyseal, I am engaged in speculation and don't insist this was how it must have happened.
You might be right, but for various reasons I think you're more likely to be wrong.
I still think that mutations must come from single progenitors
...is definitely wrong, at least with the application of the word "must", unless you know a hell of a lot more about genetics and mutation than I do, which admittedly wouldn't be difficult
I'm just not convinced it's purely natural selection at work. Natural selection works with what's already in the gene pool and, without some form of mutation, won't come up with new genetics.
well, I don't know how to convince you. It's natural selection working on random mutation that powers the engine of evolution. There is no destination, there is no one right way to do something, there is no pre-defined successful mutation list and I'm quite sure that a million million good mutations didn't make it just because.
that's why i say it takes a population to evolve, and why it takes time for a mutation to become so general that "everybody has it".
Greyseal - I don't see how mutations can derive from anything except individuals - whilst a specific mutation can occur independently the chances of that aren't high wheras a mutant gene will be passed to descendents and, as long as that line doesn’t die out, will almost certainly become part of the gene pool.
Hi Ken, I don't think you understand what I mean.
Firstly, mutations happen all the time. Every single child is a mutant since no child is an exact copy of one of the parents (at least not in humans). In addition to pure hereditry, mutations occur as well.
Finally, a particular (beneficial) mutation may originate with one individual, but for that mutation to become general it has to
a) propagate (i.e. there need to be descendants who can carry it hereditarily) b) be advantageous or at least not disadvantageous whilst doing so.
if you take humans (and this is my interpretation of the history of humans according to my limited understanding of the facts) then at some point there was a population of ape-like creatures. They separated into at least two groups.
One group set off for the plains of Africa, the other stayed in the jungle.
We will focus on the plains-group - mutations happened continuously by chance to individuals within this group (well, in the process of their conception). Those which were less hairy (either because or inspite of this!) faired in general better.
I think you agree with me there. If that's what you meant, you may as well stop here, because you are correct - although there is no reason that a mutation MUST occur in only one individual. The same random change could occur multiple times - certain changes are small enough, or the population big enough - or the same result could occur in more than one way.
unless they were immediately bald like us, chances are there will be further mutations reducing hairiness, which would again confer better survivability, which would once again mean that more and more of the population (over time) has this new-new gene change.
...and so on.
Now, my method is, to my understanding, what happened. The changes are random, and natural selection working on those changes favour, over time, certain mutations over others.