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Published online 17 September 2008 | Nature 455, 281-284 (2008) | doi:10.1038/455281a
Corrected online: 3 October 2008

News Feature

Biological theory: Postmodern evolution?

This summer a group of high-profile researchers met in Altenberg, Austria, to try and plot the future course of evolutionary theory. John Whitfield was there.

John Whitfield

"Oh my gosh," says Massimo Pigliucci, "maybe I shouldn't use that term." Pigliucci, responding to comments on his talk about how living things respond to their environment, and what it means for evolution, has just let slip the p-word.

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  • Dear Dr. John Whitfield: Yes, thanks to decades of rapid progress in biology, it is time to extend the ?modern? synthesis. I like the pictures of elegant and not-so elegant edifies, which brings up another issue implicitly in your feature article: We need to deepen and strengthen the theoretical foundation. A real edify cannot rest on the back of a turtle which is floating around. In research reality, it is known that theories of RA Fisher and S Wright are still not nicely stitched together yet. Despite some recent progress on such fundamental issue, the whole community appears to have so far ignored the foundation problem. Are we still going to pitch variation against selection? P. Ao

    • 19 Sep, 2008
    • Posted by: P Ao

  • The established definitions and applications of the concepts of mean fitness and mean adaptation of populations lead to inconsistent and contradicting consequences in population genetics, evolution, and population ecology. The Weighted Mean Fitness of all the alleles or genotypes in a population, as defined by the relative representation in the next generation, necessarily equals 1.0 by definition, under all selection regimes or conditions, and cannot therefore increase by the effects of selection. The Fundamental Theorem of Natural Selection (Fisher 1928) correctly demonstrates that the genetic changes in response to selection are proportional to the additive genetic variance in fitness. However,the implied logical consequence that the overall Mean Fitness of a population necessarily increases by natural selection is meaningless and cannot be correct. The same argumens apply to the concepts of mean fitness adaptive peaks in adaptive lanscapes. The long term ecological growth of populations is well defined by the Geometric Mean of the per generation growth factor, which necessarily equals 1.0 for all persisting populations. It cannot therefore be used to define the levels of adaptation of existing species. I think that many inconsistencies in the reseach literature can be resolved by abandoning the concepts of mean fitness and mean adaptation of populations. I will greatly appreciate any comments. Dan Cohen dancohen@vms.huji.ac.il

    • 22 Sep, 2008
    • Posted by: Dan Cohen

  • Indeed the mean fitness is generally not a good concept. You may find my exposure on related topics relevant: Laws of Darwinian Evolutionary Theory. Phys. Life Rev. 2 (2005) 117-156. doi:10.1016/j.plrev.2005.03.002 http://arxiv.org/PS_cache/q-bio/pdf/0605/0605020v1.pdf . The current theoretical tools in population genetics appear too much dominated by the mean and the variance. There are important cases which those two concepts are not enough. It will take a long time and lots of hard work to get through those points, I am afraid. P. Ao

    • 03 Oct, 2008
    • Posted by: P Ao