Oolon Colluphid

A spandrel, as I understand it, is an accidental effect of something else: it's not meant to be there, it just happens to be because of other things.

But a spandrel may become, later, an adaptation, may it not as IIRC Gould and co propose -- painting the space that happens to be produced when two arches meet, or whatever? All the spandrel idea suggests is that stuff doesn't have to start off being for what it ends up being for.

But 'being for' something is an adaptation. I wonder whether, say, colour vision started off being for colour vision. Or whether the first photosensitive lightspot was originally for producing images.

Once again, it seems to me that Gould promoted an idea which sounds like it means more than it really does. So to flip Patrick's question around, I'm intrigued, rather, how one identifies a spandrel.

For unless we consider all apparent adaptations as not-adaptations-really, as spandrels (eyes, for instance)... if they are spandrels until proven guilty of adaptation... then we know that there's plenty of adaptive stuff out there. So on finding something, it is a reasonable question to ask 'what is is for?'. If that's adaptionism, then how does one go about non-adaptionist science?

TTFN, Oolon

KC

It seems to me that, if getting rid of ectoparasites was the purpose behind human hairlessness, then how does retention of pubic hair, which through coitus guarantees CONTACT between parasite-infected areas, help their case? Ick.

KC

pz

1. I think that is a very, very poor test. There is no reason or evidence to suggest that the 'divergence' of African/Asian and "hairy" lineages has any relationship to the emergence of hairlessness in the human species (and good reason to think they are unrelated). There are also so many confounding variables that the proposed test is useless.

2. What I object to is not hypothesizing, but publishing crap like this with vague and poorly defined 'tests'...that have not been done. And then they get written up as a praiseworthy in the popular press.

This is aquatic-ape level stuff. It taints the field, and baseless, sloppy science like that gives aid and comfort to creationists.

Peez

Keep in mind that "hairlessness"* is likely to influence natural selection acting through many different mechanisms, with possibly some favouring hairlessness and others favouring thicker fur. For example, thicker fur tends to keep one warmer in cool weather and provides some physical protection, but may interfere with heat loss (in a sweating animal like a human) and make it harder to find parasites (social flea-removal would be easier without it). A change in niche could easily change the balance between these mechanisms, resulting in either hairlessness or thicker fur gaining a net advantage. Of course, hairlessness is also selectively neutral in terms of many mechanisms, and may well have provided no advantage to individuals at all. The hypothesis given is an interesting one, but even if it is supported I doubt that any one mechanism was responsible for the evolution of hairlessness in us folk.

* "hairlessness" here meaning that the skin is readily visible and more or less unprotected by hair/fur.

Peez

KC

You are right: it sounds very much like the breathless kind of reasoning behind the aquatic ape theory.

'Humans have little body hair! Neither do whales! Human hairlessness is an aquatic adaptation!'

Otters and Polar Bears, both of whom are far-better adapted to an aquatic lifestyle than man, of course, are laughing at all of this.

KC

Peez

It is certainly not a strong test, but it is a test.I do not see how such is stated or implied by the hypothesis.Perhaps, perhaps not. As it happens, I tend to agree with you here.??? You do not object to hypothesizing (which, by definition, does not include testing), but you do object to publishing a hypothesis without having done well-defined tests. Well, you are entitled to your opinion, of course.The popular press has its own issues.Obviously there are a few scientists who disagree, myself included.

Peez

ps418

Except that unlike AAT, it doesn't require any dramatic revision of currently accepted views of human paleo-ecology, and there is a clearly at least a potential fitness benefit for any feature -reduced hair or whatever- that reduces the ectoparasite load, especially if it can do so at minimal cost.

Patrick

KC

But it ignores the obvious fact that many other primates are hairy and have parasites. I think it reasonable to say that, if there was such strong selection pressure for hairlessness to avoid parasitic infestation, then man would probably not be the exception here.

If we are to propose that man's hairlessness actually has a positive selective value, it seems to me we need to first find a plausible adaptation that accommodates man being the exception. Otherwise, man's hairlessness is more likely to be a spandrel.

KC

pz

This is a bit more than my opinion. I've reviewed a few papers in my time, and papers that are full of hypotheses and speculation, no matter how reasonable they might be, wouldn't slip past me. I'd reject it and tell the authors to come back when they've got some data.

That should be SOP everywhere. I know it isn't, but that doesn't mean we should all just shrug our shoulders when empty noise creeps into the literature.

ps418

No, it does not ignore that obvious fact. Man is in fact clearly the exception in the sense of being able to manipulate fire and do lots of other things to make up for the missing hair. It could be-- and yes I'm speculating-- that while missing hair in other primates would indeed have a net fitness cost, in humans it may result in a net fitness advantage. By the same logic, the absence of hair in the naked mole rat may be an adaptation, even if all other moles are not naked, becasue of other factors that are peculiar to naked mole rat ecology. The OP itself said:

Patrick