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Evolution of hair loss

Richard Jensen rjensen at SAINTMARYS.EDU
Wed Aug 20 12:43:26 CDT 2003 

One of the hardest things to teach students, especially non-majors, is that statements such as most of those cited below, in which it is implied that something evolved TO or FOR something else, are not consistent with evolutionary theory.  I am not surprised that the author of the article presented the material in this fashion.   I doubt (hope) that the persons being interviewed described things as presented by the writer.  But, if so, woe is us!

Dick

John Grehan wrote:

> Agreed - they can be viewed as hypotheses - although testing may be problematic. Evidently hair loss took place at some time so the hypothesis has an empirical foundation. Testing when it occured is one matter, why it occurred is another. It's the 'why' that gets problematic if the 'why' is presented in terms of purpose. As far as I am aware it is not possible to test 'purpose' in evolution other than by intentional activity and that's where it seems to be more metaphysics than science. I would view why theories as inherently untestable (open to correction on that).
>
> The criterion of 'advantage' is also untestable since it seems that it is self-defining. If something exists along with the existence of an organisms then it is inherently not a 'disadvantage'.
>
> Even though evolutionary theorists generally accept that there is more to evolutionary change than natural selection (even if they won't acknowledge orthogenetic processes such as molecular drive) - natural selection is all one generally hears about when positing the origin of a structure that has an assigned function. And yet it seems there is no way of empirically testing a natural selection claim for a past event (usually what one sees is a rhetorical argument).
>
> So a clear indication that statements are hypotheses does not necessarily eliminate the possibility that some hypotheses are inherently garbage to begin with (I doubt a lot of stuff circulating in evolution education would not stand up to cross examination in a court of law).
>
> John Grehan
>
> At 09:05 AM 8/20/2003 -0500, you wrote:
>
> > Your criticisms of the information as presented are sound.  But would you have any problem with these ideas if presented as HYPOTHESES to be tested?  That's what seems missing to me: a clear indication that these are merely hypotheses.
> >
> > At 09:32 AM 8/20/03 -0400, John Grehan wrote:
> >
> >> The following link is to a NY Times article on the evolution of hair loss in humans that was brought to my attention:
> >>
> >> http://www.nytimes.com/2003/08/19/science/19HAIR.html?ex=1062266528&ei=1&en=
> >> c83c18de852e76fd
> >>
> >> The following comprise some comments and opinions - unreasonable or not - on why most of the content seems to represent teleological garbage that is more metaphysics than science when one analyses the reasoning. And people wonder why evolution has such a poor public reception. Apart from religious issues people can tell a bad product when they see it.
> >>
> >> "their idea, if true, goes far toward explaining contemporary attitudes about hirsuteness. Humans lost their body hair, they say, to free themselves of external parasites that infest fur ? blood-sucking lice, fleas and ticks and the diseases they spread."
> >>
> >> This states that one 'explanation' is an 'explanation' of another 'explanation'. Not only an explanation, but an explanation of purpose - humans lost body hair TO free themselves.... This is stating that in order to meet a future need evolution took prior action to meet that need. Maybe most people can swallow this since it feeds on religious purpose, but its not empirical science.
> >>
> >> "Once hairlessness had evolved through natural selection"
> >>
> >> "became subject to sexual selection"
> >>
> >> "bare skin would have served, like the peacock's tail, as a signal of fitness"
> >>
> >>  Not an empirical observations.  Theoretical presumptions.
> >>
> >> "The pains women take to keep their bodies free of hair ? joined now by some men ? may be now mere fashion statement but the latest echo of an ancient instinct"
> >>
> >> Metaphysical garbage.
> >>
> >> "these humid regions, dense with sweat glands, serve as launching pads for pheromones, airborne hormones known to convey sexual signals in other"
> >>
> >> Again, if something exists, it exists to serve purpose. Garbage, garbage, garbage.
> >>
> >> "the pressure of sexual selection in this case may be greater on women"
> >>
> >> Same as above.
> >>
> >> "advantage of hair loss, but they are all just-so stories," said Dr. Ian Tattersall, a paleoanthropologist at the American Museum of Natural History in New York."
> >>
> >> Agreed, but they remain pervasive and dominant in evolutionary biology (especially the education of evolution in the US). At least Ian has some common sense (perhaps why he is the only primatologist apart from the theory's originator to take the orangutan theory seriously.
> >>
> >> "But outside Africa, in northern Asia and Europe, the gene was free to accept mutations, the constant natural changes in DNA, and produced skin colors that were not dark."
> >>
> >> Possible - although problematic with respect to India and southern Asia.
> >>
> >> "As soon as the ancestral human population in Africa started losing its fur, Dr. Rogers surmised, people would have needed dark skin as a protection against sunlight. Anyone who had a version of the MC1R gene that produced darker skin would have had a survival advantage, and in a few generations this version of the gene would have made a clean sweep through the population."
> >>
> >> In this core hypothesis selection acted to serve one purpose (losing hair) while at the same time serving another (increase melanization). As Tattersall says, its a just so story. Its also a presumption that the process was powered by natural selection.
> >>
> >> "Since the silent mutations accumulate in a random but steady fashion, they serve as a molecular clock,"
> >>
> >> A theoretical proposition. Problematic.
> >>
> >> "Both are assumed to be adaptations to help dissipate heat"
> >>
> >> Teleology again.
> >>
> >> "Dr. Rogers' argument was "completely plausible," he said. "
> >>
> >> Plausible - seemingly valid, giving deceptive impression of truth, acceptability, reliability. Specious. (dictionary definition)
> >>
> >> "Chimpanzees have pale skin and are born with pale faces that tan as they grow older. So the prototype hominid too probably had fair skin under dark hair"
> >>
> >> That chimp theory again.
> >>
> >> "Humans must have been wearing clothes at least since this time"
> >>
> >> Or before.
> >>
> >> "Perhaps the body lice don't show that, he suggested, because early clothes were too loose fitting or made of the wrong material"
> >>
> >> Classic ad hoc hypothesis to protect the theory.
> >>
> >> John
> >>
> >>
> >>
> >> Dr. John Grehan
> >> Director of Science and Collections
> >> Buffalo Museum of Science
> >> 1020 Humboldt Parkway
> >> Buffalo, New York 14211-1293
> >> Voice 716-896-5200 x372
> >> Fax 716-897-6723
> >> jgrehan at sciencebuff.org
> >> http://www.sciencebuff.org/biogeography/Panbiogeography/Panbiogeography-Gate.htm
> >> http://www.sciencebuff.org/HepialidaeGate.htm
> >
> >
> > Thomas G. Lammers, Ph.D.
> >
> > Assistant Professor and Curator of the Herbarium (OSH)
> > Department of Biology and Microbiology
> > University of Wisconsin Oshkosh
> > Oshkosh, Wisconsin 54901-8640 USA
> >
> > e-mail:       lammers at uwosh.edu
> > phone:      920-424-1002
> > fax:           920-424-1101
> >
> > Plant systematics; classification, nomenclature, evolution, and biogeography
> > of the Campanulaceae s. lat.
> >
> > Webpages:
> > http://www.uwosh.edu/departments/biology/Lammers.htm
> > http://www.uwosh.edu/departments/biology/herbarium/herbarium.html
> > http://www.geocities.com/TheTropics/Resort/7156/lammers.html
> > -----------------------------------------------------------
> > "Today's mighty oak is yesterday's nut that stood his ground."
> >                                                               -- Anonymous
>
> Dr. John Grehan
> Director of Science and Collections
> Buffalo Museum of Science
> 1020 Humboldt Parkway
> Buffalo, New York 14211-1293
> Voice 716-896-5200 x372
> Fax 716-897-6723
> jgrehan at sciencebuff.org
> http://www.sciencebuff.org/biogeography/Panbiogeography/Panbiogeography-Gate.htm
> http://www.sciencebuff.org/HepialidaeGate.htm

--
Richard J. Jensen              | tel: 574-284-4674
Department of Biology      | fax: 574-284-4716
Saint Mary's College         | e-mail: rjensen at saintmarys.edu
Notre Dame, IN 46556    | http://www.saintmarys.edu/~rjensen

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