Date: Sun, 20 Feb 2000 01:18:49 -0500 From: Gregory Cochran <74771.3230@compuserve.com> Men and Dogs I know only a little of John Tooby's thoughts about the possibility of between-group genetic variations that influence behavior, but I think I disagree with him. From reading 'The Adapted Mind', I got the impression that he doesn't believe that significant differences of this kind exist or are evolutionarily plausible. I disagree on both counts. First, are such differences evolutionary plausible? We are a young species - all humans probably share a common ancestor within the last quarter million years, maybe more recently than that. Is this enough time for significant evolutionary change? Partly it depends what you mean by significant. There may not have been long enough to evolve a third eye, but there has been enough time for significant changes in intelligence, in life history, in mating strategies Look at dogs. In a similar number of generations, dogs have changed a lot. I would say that it is still possible to see that all dog behaviors are derived from those of wolves. There is no complex behavioral adaptation in dogs that does not have a recognizable predecessor in wolves, but that hardly means that all breeds of dogs are the same. For one thing, although there has probably not been time enough to develop wholly new complex adaptations, there has certainly been enough time to _lose_ them - in some breeds, but not in others. Wolf bitches dig birthing dens. A few breeds of dogs still do, but most do not. Wolves go into season in a predictable way, at a fixed time of the year; a few dog breeds do, but most do not. Wolves regurgitate food for weaned cubs, but as far as I know, dogs no longer do so. Wolves mate, and the father helps care for the cubs - as far as I know, male dogs contribute little. Any adaptation, including behavioral adaptations, that loses its utility in a new environment can be lost rapidly, especially if it has any noticeable cost. Cave fish lose their eyes in at most a few thousand years - a hell of a lot faster than eyes evolved in the first place. Next, the example of dogs shows us that variation in intelligence can develop in this kind of time frame. First, dogs in general have brains that are noticeably smaller (~20%) than the brains of wolves. Second, dogs breeds vary greatly in learning speed and capacity. The number of repetitions required to learn a new command can vary by factors of ten or more between breeds. I hate to admit it, but my dachshund probably isn't as smart as your collie; not close, even. The typical border collie can learn a new command after five repetitions and respond corrrectly 95% of the time. , while a basset hound takes 80-100 repetitions to achieve a 25%-accurate response. Dog behaviors that are not seen in wolves can also be understood as exaggerations or redirections of wolf behaviors. Border collie herding instinct must derive from wolf game-herding patterns, but it is greatly accentuated. Dogs are much more playful than wolves, and this can probably be understood as a retention of juvenile behavior (neoteny) - which is, again, far easier than evolving a behavior from scratch. Much of the ways that dogs act with humans can be understood as a new application of behavioral adaptations designed for a pack - the master takes on the role of the alpha male of the pack.. Dogs have changed tremendously since their domestication, but we can see that in some sense these are evolutionarily shallow changes, mostly involving loss of function or fairly simply exaggerations or redirections of function. The amount of time ( in generations) available for the evolution of differences between human ethnic groups probably compares with the time in generations since the domestication of the dog. If this is the case, we may expect that differences between human ethnic groups are qualitatively similar to those between dog breeds - that the differences are evolutionarily shallow, mostly involving loss of function in some groups, neoteny, exaggerations of already existing adaptations, and so on. The pattern is easier to understand in dogs since we still have wolves around. Having a presumably unchanged ancestor species around certainly helps clarify which behaviors are ancestral, but I think we could have figured it out even if wolves were extinct. Really complicated behaviors, even if they exist in only a few dog breeds, are likely to be ancestral adaptations, since there has been enough time to lose, but not to develop, such complex behaviors.. Since some dogs dig birthing dens, probably all ancestral dogs did. If any breed of dog still has male parental investment, a very complex adaptation that goes against the mammalian grain, the dog ancestor must have. And so on... And by the same argument, I'd guess that high paternal investment is an ancestral human trait; dads are traditional, cads are new. The sort of low paternal investment seen in Africa is not feasible without garden agriculture, and that's only been around a few thousand years. Other factors pushing this pattern may also be new. A tough co-evolutionary struggle with a virulent infectious disease may be able to significantly increase the heritability of fitness, since the pathogen's evolution keeps obsoleting host defenses. The heritability of fitness may end up quite a bit larger than what we'd see from mutation alone - and as fitness becomes more heritable, how healthy the dad is starts to be more important than how he acts or how well he takes care of his children - at least if women can manage to feed a family by themselves. In this situation, women who seek out good genes will do better ( have more offspring) than those who seek out good dads, and monogamy tends to gradually disintegrate. Those characteristics that are good markers for resistance to the disease become exaggerated. If this idea of Bill Hamilton's ( that high disease load, combined with female ability to raise a family without help, causes monogamy to disintegrate,) is ever true, it's must be true for falciparum malaria in Africa. Falciparum is the strongest disease in the world. A quarter of a million kids in Africa die each year because of the sheer evolutionary _memory_ of falciparum malaria - from sickle-cell anemia. Falciparum might be new - at minimum, it has probably become more intense over the past ten thousand years, with the end of the ice age and the increase in population density allowed by the development of agriculture. The Bushmen, whose way of life is as old-fashioned as anyone's, and who usually cluster pretty close to the roots of the human family tree in genetic analyses, are good dads. They have had time to change, but probably not long enough to develop something as unmammalian as being a good father. So, it looks to me as if malaria and yams crushed monogamy in sub-Saharan Africa. More exactly, it allowed a situation where having three boy friends, none of whom really do anything other than impregnate you, could become the female norm. Such a radical reshufffle of the basic family pattern is bound to have all sorts of other consequences, but I'm not sure what most of them would be, other than a much larger role for venereal disease. And no, Henry, I don't knoiw what's going on in Australia.