Re:Blushing and Biology

This is a wonderful discussion, lots of good material here. I'm not sure I can contribute much of substance. I'm probably at risk of stating the obvious in an annoying way, but one of the warning flags that goes up in my mind when someone phrases a biological question in this way is that causal models in biology tend to have multiple layers, whereas we tend to do basic inference in terms of strings of direct cause and effect.

So for example, blushing has a physiological causal sequence in the chain of events in the sympathetic nervous system, a larger systemic context in terms of how the nervous system is organized, a developmental context in terms of how it relates to the unfolding of gene expression over our lifetime, and an adaptationist context, where it can be related back to natural selection, either as an adaptive mechanism or the side effect of other adaptive mechanisms. The reason the multiple layers are important is that they each supply both "causes" and "constraints" that shape the characteristic.

Something important to remember is that skin is a living boundary between changes on the "inside" and those on the "outside," it is not just a softer version of an exoskeleton, but an actively functional organ.

Varying according to individual differences, when some people vividly imagine a hot coin in their hand, fluid rushes between the cells to cool it in anticipation, raising a "blister." Vividly imagining heat against their skin, a reaction is triggered that looks very much like the protective flushing that happens in a mild sunburn. Certain immune responses are particularly labile among the skin cells, causing slight anomalies in the rate of response to papillomavirus infections, the source of many of the folk superstitions about what makes warts go away.

Given the physiological responsiveness of this organ in general, originating long before primate social signalling, 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.

It's a particularly interesting example to me because it so clearly points out why a serious adaptation analysis of physiological activity has to go beyond the EEA of human beings, something that Pinker and other mainstream EPers surely know, but rarely emphasize in their writings. I think that's where some of the bizarre "popular" versions of EP theories come from, people take a cue from the analysts who are absorbed in human social level of analysis and forget about the larger biological picture.

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.

To me, our highest goal in biological theory of humans is to both look at our continuity with the rest of nature, and what is exceptional about us, and draw conclusions from the comparison. We lost a lot of the picture when we focus on just the human piece or just the earlier pieces, but unfortunately we have a limited attention span.

kind regards,

Todd

Replies:

Re: biology and evolutionary history, by cdn, 05/13/03

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