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Talk:Counterexamples to Evolution (view source)
Revision as of 17:12, November 15, 2008
, 17:12, November 15, 2008no edit summary
:::::Did those scientists who made that observation actualy see the giraffe's neck grow? [[User:Karajou|Karajou]] 11:46, 15 November 2008 (EST)
:::::Did those scientists who made that observation actualy see the giraffe's neck grow? [[User:Karajou|Karajou]] 11:46, 15 November 2008 (EST)
:::Huh? That question doesn't make sense (well it does, but not in a relevant way), and I think you may have misunderstood how we test for fitness correlations and natural selection in general. I was a little brief in my explanation considering that there are entire books on the subject, so let's try something a little more detailed and beginning at the basics.
:::Ok natural selection works on the idea that traits which increase fitness (the number of surviving offspring) will be passed on to the offspring of those parents (assuming it is heritable...no Lamarckian evolution). As long as the conditions remain steady, those offspring will then be able to have more offspring themselves until they make up a significant part of the population. Assuming (as Darwin and Malthus did) that there are more organisms than can be supported, only those who are best able to create offspring in this environment will be successful. "Survival of the fittest" is a gross oversimplification that spreads more misconceptions than anything else, which is why I hate the phrase.
:::So now we have the idea that natural selection ''favors adaptations which increase fitness''. Therefore, if we want to test whether or not a trait is adaptive, we can observe the number of offspring an organism has (who is in possession of that trait). This works best on traits which exist across a spectrum of phenotypes (say, the neck of a giraffe). The independent variable is the length of the giraffe's neck, and the dependent one is their reproductive success (gauged by number of matings and number of offspring). Such studies have shown a positive correlation between neck length and fitness (remember, "fitness" is just short-hand for "number of viable offspring). Also note that the specific test is one we use to judge the effects of sexual selection (in this case by intrasexual competition, based on qualitative observations of males fighting). To judge the adaptiveness of a trait from a ''natural'' selection standpoint, we simply look at the number of offspring produced (without taking into account mating success). If something is an adaptive trait using these tests, Darwinian evolution can explain it using its framework. If not, then the problem requires further investigation.
:::I hope that explains how we test the adaptive value of a trait. I don't know where the idea of "needing to see it grow" came from, but perhaps my initial explanation was too brief (I am used to teaching science majors at the college level and forget how much I've specialized, at times).--[[User:Thinker|Thinker]] 12:12, 15 November 2008 (EST)