Re: biology and evolutionary history

Todd,

Thank you kindly for your response and for warning against ignoring parts of the big picture in a question about adaptation.

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"Given the physiological responsiveness of this organ in general, originating long before primate social signaling, Jim is almost certainly on to something important when he points out that this 'signal' of central nervous system processes has an ancient origin that was already co-opted for other purposes, and then possibly again for complex primate sociality, and maybe further in humans."
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I agree completely here. Hopefully I did not accidentally presume that the physiological mechanism underlying facial vasodilation arose anew in people specifically for the proposed function of blushing. I referred to this mechanism in other contexts (be they sexual display, feeding display, or anything) as a preadaptation that was perhaps rerouted to an alternative, social function.

Please forgive my naiveté, but I am hoping that you could elaborate on a point:

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"It's like looking at an airplane flying overhead and imagining that it is there turning and diving because of the conscious guidance of the pilot, forgetting the long legacies of invention and transmission that led to the plane, the pilot, and the flight being possible. In most analyses, this would seem overkill, but in biology, if Darwin was right, then legacy is everything, and relating things back to natural selection, and not just in the human EEA, is the whole point."
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I see that it is as important to understand the evolutionary and physiological history of any adaptive trait (as well as the previous ways in which it may have been used) as it is to understand its current proximate causes and potential proximate effects. Adaptationist views are centered on conceptions of the past, including why certain behaviors increased their own rate of transmission (via gene selection) in competition with other behaviors. But how far backward in generational time should we look? When does the history of the evolution (by natural selection) of a particular behavior actually obscure our vision of the behavior we observe today? I don't see that your pilot/plane analogy applies to blushing any more than it does to other behavior or phenotypic expression in other species (I suppose you didn't mean for it to apply only to humans). Consider an (admittedly unfair) example Dawkins notes in _Extended Phenotype_: mud-daubing wasps (solitary, haplodiploid [females diploid]). Males perform "holding" behavior, grabbing females by their heads and pulling them out of their nests right after copulation, presumably to delay egg-laying and perhaps to increase the chance of fertilization (and thus transmission of male's genes). Now, the nervous mechanism responsible for this behavior may be reliant on a fixed action pattern once used for digging (except now they're dragging mates out of the ground, not dirt), which may have been derived from a mechanism for walking, which may have been reliant on nervous coordination for abdominal movement, which many have been.... All these steps, undoubtedly, are important to consider, for, as you mentioned, they pose physiological constraints. But must we doubt that the ancestral systems for walking or digging may not have been exploited again for pulling females out of their nests? How far back do we have to look before we have a sufficient understanding of the bounds within which we may look at contemporary behavior?

I sincerely hope I'm not dwelling on a misinterpretation of your response.

Thanks very kindly again,

Carey

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