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Large selection coefficients keepin' us all together

Gene ExpressionBy Razib KhanMarch 15, 2006 11:37 PM


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In my post below there is a reference to fast evolution in a relatively slow-breeding species, H. sapiens. For this to be plausible you need high selection coefficients, that is, the difference between mean population fitness and the fitness of those who are carrying the favorable allele. How plausible is this? R.A. Fisher argued against selection coefficients of large effect because he believed that mutations of large effect would usually "overshoot" the idealized fitness peak, and it was mutations of small gradual effect which were the real drivers of evolution. But recent work has reemphsized the possible importance of fast sweeping positively selected mutations across populations. And with that, I point you to How species evolve collectively: implications of gene flow and selection for the spread of advantageous alleles. Relevant sections:

Crude estimates on the strength of selection on phenotypic traits and effect sizes of quantitative trait loci (QTL) suggest that selection coefficients for leading QTL underlying phenotypic traits may be high enough to permit their rapid spread across populations. Thus, species may evolve collectively at major loci through the spread of favourable alleles, while simultaneously differentiating at other loci due to drift and local selection.

The full text is available for those without academic access at the link provided.

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