Tautology and Natural Selection

Natural selection is not a tautology, but it can be described in a way that makes it sound like circular reasoning. Yes, if 'fitness' refers to the ability to reproduce most effectively, then the fittest organisms in a population will indeed leave the most offspring. That's not saying anything about fitness.The problem lies in the fact that we can only accurately determine in retrospect what trait(s) conferred fitness upon certain individuals in a population, since we need information about every aspect of the fitness landscape: competition among variants, availability of resources, predation, parasitism, and countless other factors of greater or lesser importance. Not only that, but we need to know many things about the population itself such as diet, mating and migration patterns, etc., and the importance of any of these factors may also only be obvious in retrospect.People's view of natural selection as 'survival of the fittest' makes it easier for the incredulous to mock it as a just-so story. The better way to see it is 'elimination of the un-fittest.' This is the horrible truth of nature, and the reason we resist any attempt to ascribe a grand Design to its process: the vast majority of any population is doomed to early death without issue, and the vast majority of all species will eventually go extinct.Hence, our focus on the survivors is like trying to gauge the probability of winning the lottery by looking at a long list of lottery winners. Populations change because certain alleles are selected for out of a wide range of candidates. The machine of natural selection eliminates every combination except a few. Since the machine has so much raw material in terms of variation, we should indeed expect to see such novelty and complexity emerge from the algorithm. But let's remember that this process is also a hideously wasteful machine whose operation also requires an abominable amount of loss.{edited to correct typo}
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Quien busca, halla[This message has been edited by MrHambre, 07-21-2003]

You beat me to that one, Sy!------------------
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Like I said, the definition of natural selection can be stated in a way that is circular. I'm glad you all agree with me. Too bad I didn't make myself clear concerning the definition of fitness.I'll accept that fitness is only meaningful in terms of reproductive success. The meteor hurtling toward the Yucatan was the missing variable in the fitness equation that meant the difference between the fitness of most dinosaurs and their extinction. In contrast, the humble peacock carries plumage that no one would consider advantageous in the fitness equation except for the fact that peahens are attracted to it. An organism can be not-well-adapted to its environment and still win the reproductive lottery.Fitness can't be defined in terms of an objective set of traits, however. What makes a cactus fit is not the same thing that determines fitness in a walrus. We have to examine each organism in its fitness landscape to discern what determined its fitness, which traits were selected for at the expense of so many others.------------------
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But I would consider the peahens apart of the peacocks environment (am i using the term too loosely?). And if ones purpose is to reproduce, then they'd have to be a factor in the equation. So wouldn't the peacock with the flamboyent plumage be the best adapted to its environment?

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If you want to make the charge of tautology even more acute, sure. In terms of susceptibility to predation, however, the peacock with the biggest plumage is at a disadvantage, regardless of its popularity with peahens.Our definition of 'fitness' means 'having most reproductive success,' independent of any objective measure of environmental adaptation. If you want to make 'probability of reproductive success' part of our definition of well-adaptedness, then we're back to square one.------------------
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That's our Sy, he speaks for himself.------------------
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I'd say the phrase can be interpreted as "The best able to reproductively succeed more often reproductively succeed." And the "best" can be from an engineering perspective looking at a problem. That does seem tautologous, but I don't think it is.

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I think we all agree that reproductive success is the measure of fitness. It's what conferred this fitness upon the organism/allele that your engineering perspective can discern.------------------
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As Mammuthus pointed out, the engineering analogy falls flat as the only way we can call an organism "fit" is by the post hoc analysis: if it survived, it was fit enough to do so.

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The engineering assumption would only work, in other words, if we knew absolutely everything relevant about the fitness landscape, including freak contingencies. How many of us wouldn't have had our money on the dinosaurs as trophy winners? Not even the most stringent engineering analysis could have made us aware of the comet hurtling toward Earth that would change the fitness landscape so drastically.------------------
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Were the asteroid impact survivors survivors due to pure chance
or because they were fitter with respect to the radically
modified environment?

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Completely rhetorical question, and rightfully so. As you have mentioned before, the ancestors of modern birds survived the extinction of the rest of their cousin species.Granted, this aspect of the dino fitness landscape would have been so difficult to predict at the time that we would have been justified in considering such a drastic change highly improbable. And as Bill Dembski will tell you, highly improbable events never happen.I realize Gould felt that mass extinctions and other contingencies were weaknesses in the Darwinian framework, but I fail to see how dramatic changes in the fitness landscape somehow invalidate the concept of natural selection.------------------
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