How Powerful Is Natural Selection?  “Biologists May Be Deluding Themselves”

Andrew P. Hendry (McGill University, Montreal) is no creationist; Darwinian evolution is a given in his News and Views piece in Nature¹ this week.  But he cautioned his fellow evolutionary biologists not to make overconfident claims about the power of Darwin’s most famous concept, natural selection:

Adaptation by natural selection is the centrepiece of biology.  Yet evolutionary biologists may be deluding themselves if they think they have a good handle on the typical strength of selection in nature. (Emphasis added in all quotes.)

Presumably, nobody does have such a handle.  Darwin himself thought it was slow.  Later biologists, like Kettlewell with his peppered moths, thought it was fast and strong, able to make substantial changes quickly.  Hendry gives historical examples of the pendulum swinging back and forth on this issue, to the point he is not sure what to think.  In 1998, Kingsolver et al. returned to the belief that selection was weak, and “most estimates of selection were non-significant and centred around zero.” A particularly worrisome finding, Hendry says, was that “most studies did not have sufficient statistical power to detect typical strengths of selection” even if it were present.
    But then Hereford et al. in 2004, using the same data, came to the opposite conclusion, finding “extremely strong selection overall.”  He based his ideas on a benchmark method: “selection estimates for individual traits are standardized to allow comparison with the expected strength of selection on fitness itself.”  Hendry is not convinced.  He repeats his warning:

These results raise some perplexing questions.  Principal among them is the apparent paradox that typical studies of selection do not have the statistical power necessary to detect selection that appears unrealistically strong.  Unfortunately, this paradox will not be resolved simply by accumulating more data of the same ilk, as all reviews identify problems with our current methods.  How, then, are we to obtain a good handle on the true power of selection in nature?
    Evolutionary biologists will have to resolve this uncertainty by determining how best to measure and judge the strength of selection, and by conducting more robust studies of selection.  Meanwhile, we are only deluding ourselves that we have a good handle on the typical power of selection in nature.  Once we do, we can begin to investigate how humans are changing selection pressures, and whether populations and species will be able to adapt accordingly.

¹Andrew P. Hendry, “Evolutionary biology: The power of natural selection,” Nature 433, 694 – 695 (17 February 2005); doi:10.1038/433694a.

A more damaging admission by a Darwin Party spokesman could hardly be found.  The entire spectrum of life, from the earliest reproducing sack of chemicals to modern human astronauts, is supposed to be the product of natural selection acting on numerous, slight modifications.  Natural selection is an icon in our civilization, the stuff of myth and legend.  The phrase Darwin grew to prefer, survival of the fittest (whatever fitness means; see 10/29/2002 entry) represents the most powerful force in the universe, a materialistic creator omnipotent enough to evolve not only an Earth filled with millions of diverse organisms – from sponges to penguins to dragonflies to dinosaurs to horses to mushrooms to petunias to oaks – but potent enough to fill unknown worlds with alien biology and weird life beyond our wildest imaginations.  Natural selection is the staple of science fiction movies; it is the cardinal doctrine of the state secular religion.  And now they tell us they don’t even know how to measure natural selection, or to tell if it is weak or strong, fast or slow, or even detectable by statistical methods.
    So if the centrepiece of evolutionary theory is this sickly, how do you like the rest of Charlie’s table?  Better not swallow anything he puts in front of you.