Yesterday on NPR, or perhaps the day before, I heard a spot on the domestication of the cat. Current theory proposes that early, proto-domesticated-cats would have been valued for their abilities to catch and destroy vermin. We can also propose that those cats who were encouraged to stay (or at least, not chased away) would have been those who were the most pleasing to the people in need of vermin control. Part of a cat's appeal would be the nature of its voice, and as cat owners know, there is something appealing in [most] house cats' calls. There is something endearing about the timbre, volume, inflection - something about their calls is socially encouraging.
The speaker compared the socially encouraging nature of house cats' voices to those of wildcats in the zoo, which he found sounded "permanently angry". Truthfully, I might be permanently angry if I was incarcerated in a zoo, and I don't know that I've ever seen a zoo inmate that I'd have called happy, but the point for this discussion is that wildcats, which I gather are genetically similar enough to house cats to successfully mate with them, have voices that are much less pleasant to our ears. The proposal, therefor, is that humans have unnaturally selected house cats for their voices, and for other features we find desirable.
At first glance, this may not seem much different than any form of natural selection - those cats whose traits best enabled them to survive in the world of humans flourished, while those cats who always seemed to be pissed-off failed to survive and procreate. But to look at the issue this way overlooks one key difference. This selection of cats was driven by human intervention. There may not have been a plan behind it, but there was definite intent - "oh, this cat is cute and has a pleasant voice; I think I'll feed it and provide it with shelter."
The phenomenon we describe as natural selection looks only at the relationship between the individual and its environment, and does not consider any guiding intelligence on the part of either. In the case of house cats (and dogs, and domesticated species generally) we find an element of intelligent design, for although we cannot design a species from scratch (yet), we can selectively breed individuals to enhance traits we prefer and reduce traits that we don't. We have hijacked Darwin.
Which leads me to a discussion of healthcare. Individuals who in the natural course of events would die without reproducing are allowed, through the tools and techniques of medicine, to survive, and their genes, including those that made them sickly and inclined to die, are preserved in the gene pool. Thus, instead of naturally shedding undesirable, and even harmful, genes; which would keep the gene pool and the species strong; we keep them and make our species as a whole weaker.
If our medical technology ever gives up or out, then we as a species may be doomed.
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The way I conceptualize these issues is: Humans are part of nature. The human world is part of the natural world. Human 'intelligence' is subject to evolutionary forces in the same way that cat voices are. There's a good book about this: Why We Get Sick, The New Science Of Darwinian Medicine. Also, Jared Diamond's book The Third Chimpanzee has some wonderful sections about how humans have unconsciously sexually selected ourselves.
Illness has its own set of evolutionary aspects - the more severe an illness is, the less able it is to procreate. Ebola is so deadly that it frequently burns itself out before it can spread: it incapacitates and kills its host before the host can pass it along. Less virulent strains survive to be passed on to new hosts. At the same time, those hosts least able to survive the infection are more likely to be killed off, and their genes lost, so over time the hosts become stronger and the pathogens become more benign. Toxoplasmosis creates problems during pregnancy, but is otherwise apparently entirely benign (in those with competent immune systems).
My point has to do with genetic conditions which predispose to death, e.g. heart defects, asthma, severe depression, hyperlipidemia. In any other species, individuals suffering from these conditions would die off and their genes would be lost. But medicine enables us to keep those defective genes and pass them on to subsequent generations.
Another way of explaining this all is to propose that we in the Western/industrialized nations are cyborgs: we cannot live independently of our technology.
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