On Sun, 1 Jun 97 10:17:12 CDT, Wesley R. Elsberry wrote:
WE>I managed to drive through the fringe of the bad weather in the
>Austin area this week and live to tell about it, so I thought
>I'd drop an answer to one of Stephen's questions.
>
>About soft selection...
>
>Futuyma's "Evolutionary Biology" gives the following:
>
>[Quote]
>
>[...] Some genotypes (such as lethals) may be unconditionally
>inferior; their death lowers population density, a process that
>Wallace (1968b) has termed HARD SELECTION. Population fitness, as
>measured by density, in such instances clearly increases as such
>genotypes are eliminated. But very often, superior genotypes merely
>replace genotypes that are relatively, not absolutely, inferior; and
>the population density, regulated by an extrinsic density-dependent
>factor, does not change as selection proceeds. In this instance,
>which Wallace terms SOFT SELECTION, the increase of a population's
>fitness by selection is not measurable in ecological terms.
>
>[End quote, pp.331-332]
>
>Mayr addresses "cost of selection" on pp. 594-595 of "Growth of
>Biological Thought" and gives reasons to suspect that Haldane's
>assumptions were not reflective of reality. Mayr cites the
>*observed* rapid rates of evolution in populations as well as
>the *observed* high incidence of heterozygosity in populations
>to argue that Haldane's analysis does not model reality well.
>The major factor that Mayr identifies is Haldane's assumption
>of large populations, which is contrary to where we observe most
>evolutionary change taking place.
Thanks. This appears to be another of the many obstacles to
Neo-Darwinist macroevolution taking place.
Walter says he has sent me his response but in my last but one mail
download, I hardly got any mail. Something must have gone wrong.
So I have asked him to re-send it.
Regards.
Steve
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