I occasionally read the discussions of evolution at various sites. It strikes me that one common misunderstanding is the confusion of natural selection. Specifically the distinction between selection for and selection of. This is especially true among critics but also pops up alarmingly often when people discuss evolution and philosophy.
Selection for entails what natural selection's object is. Now in one sense there is, of course, no object. Individuals either survive and reproduce or they don't. But what affects their survival is what is being selected for. So let's say some species encounters a situation where their normal food supply dies out for some unknown reason. There's an other possible food but it's harder to utilize since it flies very quickly and erratically. Some mutation allows them to eat this food more reliably by being able to track these swiftly flying bugs. The individuals that can do this are more apt to survive to reproduce. What is selected for is this ability to eat and use this other food supply. What is also selected for is the ability to track these bugs.
Now let's consider this ability to track the bugs more abstractly. The mutation in question gave not only the ability to track our flying bugs. It gave the ability to track quickly moving objects - not necessarily our bug that our creature is eating. This more abstract (or general) capability is what we call our selection of. This includes detecting bugs of course but much more. That "much more" may become significant latter on if the environment of our species changes.
For natural selection explanations to "work", specific selection pressures giving rise to selective advantages for specific features need to be defined, which is not always easy to do, given limited information about past environments. (Why, e.g., do humans have an opposable pinkie? It permits fine motor coordination of the hand, such as playing the piano, but it's not clear what it would have been selected for. The capacity to sift for seeds and the like has been suggested, and obviously it effects the grip on objects, which might effect throwing, and obviously it would have facilitated tool-making, but the exact conditions under which it would have been selected aren't clear. The opposable thumb, which the opposable pinkie was re-adapted to, was an arboreal adaption of primates). The problem with strict adaptionist explanations for all the features of an organism is that those features might well have arisen at different times in response to different environments and pressures, and, of course, might be subject to subsequent re-adaption for different functions. So while natural selection for adaptive fitness has a general explanatory plausibility, very often the particulars are missing, (such that one could never assuage all the objections of those prone to be willfully "skeptical" on the matter), and "reverse engineering" precisely misses that organisms are not engineered or designed in the first place, so that one would expect the round-aboutness of both general robustness for survivability and contingent path-dependencies with re-adaptions, in additions to precise adaptive fitness, to be manifested in the features of organisms.
The extent to which one could postulate any general lawfulness for natural selection is severely limited by the diversity of phenomena and conditions, and I'd doubt that one could claim any tendency to evolve more general capacities, other than the limits to strict adaption of all features that I noted. If there is a general rule, it's that populations of a species must maintain sufficient variation, else the species is liable to extinction with changing environmental conditions, (as all species eventually are, whether or not they branch off into the formation of new species). A given behavioral strategy, for example, might be dominant in a species population, but it would be balanced with subordinate behavioral strategies among some subsets of the population, which might later become dominant under changing environmental conditions. It's only the maintenance of sufficient variation in species populations consistent with the amintenance of the stable "identity" of the species that constitutes the future adaptive "potential" of species, (which, of course, would be why sexual reproduction with its alleged twofold cost is so dominant). But I think that the most that could be claimed for any more abstract or generalized capacities attaching to the adaptive features of organisms is that they might minimally accrue to successive, path-dependent readaptions of those features. In general, however, there is no tendency toward increased complexity in organisms. If there were a general "law" for natural selection, it would be "faster, cheaper, and out of control", with such positive feed-back put in check externally by other positive feed-back mechanisms in the environment of the species. The most that could be claimed for the emergence of complexity in organisms is that the longer evolutionary processes run and the greater the diversity of ecosystems, the more the probability of the emergence of more complex organisms increases through the co-evolutionary "arms race", though always as an exception to the rule, among relatively few species, and at low probabilities.
I certainly agree that as a practical issue guessing what is selected is a hugely difficult problem. Even in populations we can track empirically let alone most of the populations in discussion. While such questions always are, to some degree, speculative, I think that correspondingly this simply means that there are greater or lesser degrees of confidence. But even somewhat weak evidence can still produce good arguments. Otherwise philosophy would be entirely impossible. (grin)
Well, I'm as "guilty" as anyone here. But, while I do think the broad paradigm of evolution by natural selection is cogent and that there is plenty of valid evidence for it, which wouldn't be readily overturned, it's worthwhile examining the constraints that such explanations are under. I tend to take objection to accounts, whereby such constraints are treated as the very source of "certainty",- (as, in general, I think the appeal to certainty misunderstands or misrepresents how scientific knowledge and evidence actually "work"). I do think "we" will gradually come to understand and explain some of the constraints involved in "human nature", though in piece-meal fashion rather than in terms of a declared "program", but I don't think that such understandings will ever amount to a "constitutive" explanation of just who and what "we" are. Oddly, some of our best knowledge of the constraints that we are under come from cases of defects or disabilities, which means that "we" are involved with normative accounts of just what our "normal" potentials or capacities should be. And, on the other hand, our understanding of non-human biological nature comes in terms of eco-systemic constraints and parameters, which "we" do not quite understand or control, but to which we must relate ourselves and for which we must be helplessly responsible. It's strange, but "true" that evolutionary thinking might alter, not just our conceptions of our selves, but our conceptions of non-human nature, in such a way that both are rendered more indeterminate, more contingent, and yet more "necessary" in their cross-implications. "Philosophy" might be just another word for nothing left to lose.
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Blogged by Clark Goble