Mystery solved. How and why human ancestors became hairless.

[mistermack]

Click link below to see how we lost our fur. (According to me that is).

(Link)



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[Gawdzilla Sama]

too long, didn't click.

[Tero]

It had a lot of words. I think it was the wimmin, got tired of picking lice. Less hair, less lice.

[Gawdzilla Sama]

It had a lot of words. I think it was the wimmin, got tired of picking lice. Less hair, less lice.

We know rather closely when pubic lice diverged from head lice. The lack of cover between the two areas was most likely responsible for that divergence.

[Rob]

Why the fuck is it written in different colors?

[Azathoth]

AARGH MY FUCKING EYES!!! Do you seriously expect anyone to be able to read that shit?

[piscator]

[Pappa]

Click link below to see how we lost our fur. (According to me that is).

(Link)



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There's a fatal flaw in the reasoning. We lost our fur a long time before we started wearing clothes.

[Trolldor]

Sounds oddly familiar...

YOU ARE EDUCATED STUPID.

[GenesForLife]

There has been great attention paid to man’s comparative hairlessness, when compared to other apes. The reason we find it striking is that this is the difference that most catches the eye. However, appearances are very deceptive. When you examine the facts, it is a tiny and rather insignificant difference.

I never found it most striking at all, so you may want to change 'we' to I , as far as insignificance et cetera is concerned, it is a subjective viewpoint

To begin with, man is very definitely not naked. We have a great deal of hair, but most of the strands are very short and fine. So the difference is actually a question of the degree of development of the existing hair. Yet most people seem to think ‘apes are hairy, we are not’, but the truth is we are all hairy. Some modern people can be extremely hairy, usually those with ancestry leading back to a northern race.

Citation please, especially when you talk about what people seem to think, for one, and secondly the stats for those people, backed by peer reviewed literature citations.

We have no way of proving when man started to lose his ‘coat’. This is because hair does not fossilise well, or often, and we have no fossil evidence from ancient times to give us even a clue. So we don’t know when or why man became less hairy. There has, however, been much speculation on the subject, and many fanciful hypotheses have been put forward in an attempt to explain why man is so relatively hairless.

FFS, you never learn, the reason why a phenotype manifests is NOT the reason a phenotype is selected for.

This is a bit of a mystery to me. It has always seemed perfectly obvious to me why we are comparatively hairless. It’s because we don’t need body hair! It’s because we wear clothes, and we can make a shelter! Why look for complicated reasons, what’s wrong with the obvious? We all know that we could not survive as we are, even in Africa, without any clothes or shelter.

Hairyness was lost as a trait because there was nothing deleterious in losing it, there was therefore no selective pressure acting on it to keep it in the gene pool, and now it will get tricky, were hairs lost first or was clothmaking discovered first, was there an overlapping decending-ascending double variable continuum involved?

If we had no clothes or shelter, we would need body hair. Body hair has many functions, but the most basic is to keep the body warm and dry. Animals such as mammals and birds, which are warm blooded, need to maintain a constant high body temperature to survive. Each species evolves its own strategy to achieve this, and there are many factors involved, including body size, behaviour and metabolic rate, as well as the quality of the coat of feathers or hair. Environment is also a big factor, and how a creature interacts with its environment is often crucial.

Evolution is not a voluntary process, and your statement gives me that impression, again, hair loss first or clothes first? ane the evidence for this would be?

Whatever you've mentioned are the parameters that may affect selection, selection shapes variation into adaptive traits.

Speculation on human ‘nakedness’ has usually centred around what possible advantage we gained from losing a thick coat of hair, but it’s far more likely that it was the overcoming of the disadvantages of hairlessness that was the real spur.[/quotes]

Assumption of strong adaptationism, it could very well be that an early genotype change was neutral and spread by drift alone, to assume everything is either beneficial and thus likely to be placed under strong adaptive selection or deleterious is a false dichotomy, get yourself copies of Mootoo Kimura's work, please.

To illustrate this, consider the Chimpanzee. There may be many potential advantages to a Chimp, if he were to lose his coat. The main ones are a reduction of parasites and more efficient cooling, and these could have led to a more hairless Chimpanzee, but they haven’t. This is because Chimpanzees with thin coats must suffer in cooler, wetter periods, especially at night.

The current lineage hasn't had the necessary genotypic change, end of, if only selection were to be of concern, then we'd expect to see variations, do you have a citation to back your point up?

So a coat of hair is a mixed blessing to Chimps. Sometimes it’s a problem, as it makes them hot in hot weather, and provides a home for parasites, but at other times it is a lifesaver, as it prevents hypothermia. If a Chimp could take off its hairy coat, and just put it on when it needed it, it would have the best of both worlds. They have never found a way to do this, so today we have hairy chimps.

Evidence please, especially to the end that hairyness in chimps is under positive selection.

Once our ancestors came down from the trees, and began to walk upright and hunt, they were able to carry things with them such as animal skins or large leaves, which could help to keep them warm and dry until the weather improved. So they achieved what the Chimpanzee never did, the best of both worlds. In a hot place like Africa, once the thick coat became non-essential, losing it became a real possibility.

Losing it would have been possible regardless of whether it was non-essential or not, especially if phenotypic change could be neutral, the Phenotype does not dictate the genotype or the changes to the latter, phenotypes only dictate selection.

In fact, it is quite normal for mammals that don’t suffer from the cold and wet to lose their hair. Large mammals are the most obvious examples, especially those with the most rounded shape. This is because their surface area is small in relation to their body mass. Elephants, Rhino and Hippos are obvious examples. A Giraffe on the other hand has retained its coat, even though it is very large. This is because of its shape. It has long thin legs and neck, and a deep flattened body, and so has a relatively large surface area, which means it would quickly lose heat in cold wet conditions, if it had no coat.

No selection pressure = free to mutate, no shit, Sherlock.

Our hairy ancestors were varied in the degree of individual hairiness, just as we are today. But they began to find new ways of keeping warm and dry during the cold wet periods, by carrying an animal skin or large leaf, and throwing it on until the weather improved. They also began building crude shelters, and a probable combination of these two strategies meant that cold wet periods were no longer such a problem. The less hairy then became better off than their more hairy brothers and sisters, as they were more comfortable in the heat, and less prone to parasites. At least one population then made the change and became smooth skinned.

Citations please, again, especially with the varying degrees of phenotypic variance you are proposing, and what about testable predictions.

So to sum up, a hairy coat in a hot climate has advantages and disadvantages. Once our ancestors found a new way of gaining these advantages, they were just left with the disadvantages, and so hairiness could be bred out of an isolated population.

Evidence please for that happening, and also the proposition that said thing happened after the invention of clothing et cetera.

This process could never have happened in a cold climate, as the benefits of losing the hair would be so much less. It is virtually certain, then, that it happened in Africa. It is also very unlikely that it happened in a place that had marked differences in the seasons. If there are extremes of temperature, then you are unlikely to lose a fur coat. So the most likely place for hairlessness to come about is near the equator, in tropical Africa. Somewhere where extreme cold is rare or unknown.

Citation please

The actual behaviour of shelter building and clothing wearing could, and probably did, arise elsewhere, somewhere where the cold and wet were more of a problem. It would not inevitably lead to hairlessness, far from it. It would just be another aid to comfort and survival, and would expand the range of areas that our ancestors could inhabit.

Without the apposite genotypic changes it means fuck all.

However, beneficial behaviour can spread and migrate in a population of intelligent creatures, especially apes, which have an inborn instinct to copy and learn from each other. When this behaviour reached an area that had a very consistent warm climate, where night and day were both warm, and the seasons varied very little, then conditions would have been very suitable for a smooth skinned human to evolve. Somewhere near the equator, at low altitude, fits the bill very well.

Conditions would have been suitable for hairlessness to be neutral/adaptively beneficial as a trait.

So when our direct ancestors eventually spread to colder parts of the world, they must have been already smooth skinned, and they adapted to the cold by becoming more skilled in the art of making clothing and shelters, and by living in caves in the very worst weather. And as we had already learned to make fire, we had the tools we needed to survive in much colder parts of the world. We have retained body hair around the genitals, on the head and armpits, and it seems likely that these are sexual signals whose benefits have outweighed their disadvantages.

Citation please.

However, just because conditions became suitable for hairlessness, that doesn’t mean it was bound to happen. Regular interbreeding with the rest of the population would ensure that a coat of fur was retained, even in areas where there was little need for it. In fact it’s likely that this theoretical population that became hairless became physically isolated in some way, from their cousins on the rest of the continent. This could have been due to some natural barrier, such as a mighty river, that prevented the majority hairy population from interbreeding with the isolated population that were losing their coats. Outbreeding would have to be prevented for a significant period, for a new, relatively hairless species to emerge.

Is this consistent with mtDNA divergence showing the establishment of founder effects? Can we see indications of a bottleneck at the postulated time? Remember that drift alone can result in the spread of mutations, or, once there is no selection pressure for retention, several different mutations can produce the phenotype.

This situation can and does often arise in nature, and today we can see a similar situation in Africa, where common Chimpanzees are geographically separated from Bonobos, sometimes by no more than a wide river, but this physical separation has led to marked differences in two closely related species of ape.

For your assertion to be true for this example , you must establish that Chimpanzees and Bonobos both descended from two halves of the concestral population.

In the case of our own ancestors, hairlessness would have been an extremely visible difference between individuals. Genetically, it may be a tiny difference, but mentally, to the individual, it is striking. Cover a modern human with hair, and let him walk along a beach in a swimming costume, and everybody would stare. He would certainly be looked on as a freak, and it’s very doubtful if he would appeal to the opposite sex! Conversely, if you shaved a Neanderthal man all over, and gave him a modern haircut, he would probably not get a second look on the same beach. Appearance is that important to our human mind.

Sexual selection can alter what traits are deemed attractive or determine mate choice, big deal, point being?

So it’s highly likely that, once an isolated population of our ancestors had lost their coats, they were then most unlikely to interbreed with their furry cousins when they later encountered each other, after the period of isolation ended. The visual difference would have been just too much, and enough to convince both parties that the other was a totally different creature. Interbreeding may have been genetically perfectly possible, but culturally impossible. Nowadays, hair is an extremely important sexual signal, and it must have been just the same back then. A man or woman with a full coat of fur would struggle to find a partner today, and why should it be any different back then, to either party?

Erm, that either implies that the hairy population completely died out (1) or that the furry must have found the hairless attractive (which is required to, in the absence of (1) spread the trait in the gene pool) AND the hairless would've mated with the furry, which could render bare the validity of your sexual selection hypothesis. It would appear to me that until SOME stage at least interbreeding would be possible between the hairy and the not hairy, otherwise the smoothies would have been driven to a bottleneck mediated extinction event.

We humans are extremely visual in selecting sexual partners, and also in how we react to strangers. Other animals use scent, or elaborate rituals to identify their own species, but we use our eyes. The instinct is still within us to fear those who look different, and to attack them if they move into our neighbourhood. We suppress these instincts nowadays, but they are still there. Forty or fifty thousand years ago, our ancestors had none of these civilised inhibitions, and such a drastic visible difference as a full coat of hair would almost certainly lead to violence, rather than interbreeding. This is especially true of a time and place where clothing, if it existed, was rudimentary, and only required infrequently.

See my last post and understand why immediate reproductive isolation is such a blind assertion.

Trying to put a date on our loss of a coat of hair is interesting, but difficult, because of the lack of fossil evidence. If one accepts that it was becoming upright that was the spur, then it could possibly go back five or six million years. If it was the availability of the skins of larger animals that made the difference, then it could still date from two or three million years ago.

Molecular divergence.

If it occurred later that this, then it is possible that homo erectus and all early homo sapiens were fully covered with hair, and that it was only our own variety, homo sapiens sapiens, who became smooth skinned.

Yup, point being? Still doesn't help your sexual selection hypothesis.

This raises the interesting possibility that the first European and Asian humans were actually as hairy as Chimpanzees, and their Neanderthal descendants would certainly have been similar. When smooth skinned modern humans later spread to Europe and Asia, it may have been this highly visible difference that made interbreeding between the two so uncommon. (Genetic studies indicate that modern humans replaced all the other human lines, including Neanderthals, rather than interbreeding with them). The latest work on dna extracted from Neanderthal bones indicates that our own ancestors split from those of Neanderthals about half a million years ago, without any significant subsequent interbreeding.

Citations please.

In fact, recent work on human genetics indicates that all the humans now on the planet can be traced back, through an unbroken female line, to one individual female in Africa that existed roughly 170,000 years ago. Also, there is evidence that the total size of the population dropped as low as 40,000 about 40,000 years ago. The natural assumption has been that our ancestors almost became extinct, but this is not necessarily so. It may also be that this small population became physically isolated, lost their coat of hair, and then subsequently never interbred with the majority population when the isolating conditions disappeared. Instead they kept to themselves, competed successfully, and eventually replaced all their hairy cousins all over the world.

erm, fail, if you are isolating a small population, to the tune of extremely few humans, you're putting them at risk of extinction by bottleneck effects, there MUST have been interbreeding for the trait to spread through the gene pool.

While some of this is just interesting speculation, it is a certainty that the human race did go through this process at some period for some reason, or we would all still be covered with fur. It’s also virtually certain that it happened in Africa, as most of the rest of the world experiences cold periods that would have prevented it. And given the way it ties in so well with the genetic evidence, there must be a strong chance that this is how our ancestors did evolve.

The art of stating the bleeding obvious.

However, it will be very difficult to confirm any of this, unless scientists can somehow identify the ‘hairy’ genes from the remains of Neanderthals, or other ancient humans.

Comparative analysis of hair development and expression pathways in modern humans and our ape cousins will be enough.

Edit- fuck the quoting.

[GenesForLife]

And do please understand,despite how dramatic it may seem, that to assert that a mystery is solved when it actually is just a load of speculative codswallop that may have critical flaws is intellectually dishonest, Mack.

[mistermack]

Why the fuck is it written in different colors?

Who gives a toss? Not me. The ones I hate are black background with white writing.

AARGH MY FUCKING EYES!!! Do you seriously expect anyone to be able to read that shit?

Lots of people can read these days. This was really aimed at them. There are websites with lots of pictures and cartoons, you should get a grown-up to find them for you.

[GenesForLife]

FFS, Mack, readers give a toss, your color scheme really does make some of the cretinist ones I've seen look gorgeous, a stylish looking site can add weight of perceived legitimacy in readers.
Ghatanothoa, you could have easily copied the text into word and read it without the appalling colour scheme.

[mistermack]

I never found it most striking at all, so you may want to change 'we' to I , as far as insignificance et cetera is concerned, it is a subjective viewpoint

Genes, you're arguing with one word for the sake of it here, rather than looking at the meaning of what's said.
I wrote "we", meaning "most people". The meanings pretty clear.

We (sorry, most people) don't walk around naked in public today. If we did, WE would find anybody covered with a coat of fur like Chimpanzees and Gorillas rather striking.
Shave a chimp and dress it in clothes and they are weirdly human. That's why I said WE find it STRIKING. The complete covering of hair is the most eyecatching difference.

Citation please, especially when you talk about what people seem to think, for one, and secondly the stats for those people, backed by peer reviewed literature citations.

Fuck me Genes, this is a chat forum. If you're going to write "citation please" after every statement, you're trying to treat it like a dissertation. This is a piece of opinion, for peoples amusement.

FFS, you never learn, the reason why a phenotype manifests is NOT the reason a phenotype is selected for.

Genes, have you swallowed a dictionary? For fuck's sake talk English.

Hairyness was lost as a trait because there was nothing deleterious in losing it, there was therefore no selective pressure acting on it to keep it in the gene pool, and now it will get tricky, were hairs lost first or was clothmaking discovered first, was there an overlapping decending-ascending double variable continuum involved?

Oh Jaysus spit that dictionary out. It really doesn't add any weight to what you say. It may bluff some people, but it really just makes what you are saying unintelligible.
re the first part, that's what I said.

The bit about which came first shows you're not understanding how evolution happens. You just don't have a first and second. You have a VARIED population, carrying different genes. Some are extremely hairy, some are less so. The EXTREMELY GRADUAL AND VARIED beginning of clothes and shelter-using would gradually reduce the advantage of "hairy" genes and favour "less hairy" genes, over a long period.

A noticeable change in the characteristics of the population as a whole emerges from an extremely blurry soup. Saying "this happened first, then that happened" doesn't tell the true story at all.

Evolution is not a voluntary process, and your statement gives me that impression, again,

Ok, I wrote the word strategy. People do it all the time, but it's wrong. Mechanism any better?

Assumption of strong adaptationism, it could very well be that an early genotype change was neutral and spread by drift alone, to assume everything is either beneficial and thus likely to be placed under strong adaptive selection or deleterious is a false dichotomy, get yourself copies of Mootoo Kimura's work, please.

Chimpanzees, Gorillas, Bonobos, Orangutans, Gibbons, Baboons, etc etc etc, etc. etc. etc. ALL fully hairy. Man NOT.
Does that look like it's "neutral and spread by drift alone" to you?

The current lineage hasn't had the necessary genotypic change, end of, if only selection were to be of concern, then we'd expect to see variations, do you have a citation to back your point up?

Genetic variation is fundamental to evolution. I'm making an ASSUMPTION that, as our ancestors had enough genetic variation to change, Chimps would too. Sometimes you just have to assume things, otherwise you would never get anywhere. I think it's a safe enough assumption to make.

Evidence please, especially to the end that hairyness in chimps is under positive selection.

Chimps are hairy. Nearly ALL mammals are hairy. There are THOUSANDS AND THOUSANDS of hairy mammal species, there are how many hairless?
Sometimes you have to go with the bleedn obvious.

Losing it would have been possible regardless of whether it was non-essential or not, especially if phenotypic change could be neutral, the Phenotype does not dictate the genotype or the changes to the latter, phenotypes only dictate selection.

See the above answer. Where are all the hairless thirty kilo mammals?

No selection pressure = free to mutate, no shit, Sherlock.

You've really lost me now. Mutations happen all the time.
Do they spread in the population, or die out? Selection determines that. The need for mammals to keep their temperature constant is a BIG, CONSTANT SELECTION PRESSURE.

Citations please, again, especially with the varying degrees of phenotypic variance you are proposing, and what about testable predictions.

That's my opinion I'm offering. That's crystal clear.
I assume variance, because we evolved. Cause and effect.
How the fuck to you predict evolution, and then verify it?
It's not physics. Or do you mean, make some fake predictions, and match them to what happened? Any fool can do that, it's hardly a genuine prediction when you know what happened.

Genes, I'm taking a break here, or giving up here. Thanks for your comments. BUT :
Constantly writing "citation needed" after an obvious opinion is a waste of time. And please dump that fuckin dictionary. It's what you say, not bullshit terminology that makes a difference in the end.
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[Gawdzilla Sama]

"Tell me which words you don't understand and I won't use them."