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April 05, 2005

What people should know about evolution

As a follow up to Why evolution doesn't make sense, below I offer two examples where a deeper understanding of evolution might be useful.

A few months ago there was a fear over avian bird flu spreading to humans. Wendy Orent, author of Plague, was making the talk show rounds trying to calm everyone down. Her reasoning was plainly Darwinian: an extremely virulent pathogen like the avian bird flu could only flourish in the artificially dense concentrations of chickens in East Asia. Since humans live at a much lower density such a virus would not spread easily as the carriers would die before they could pass the pathogen on to someone else. Plain ho hum Darwinian logic.

Another example is the "human universal" where female infidelity is never treated more lightly than male infidelity, and in fact, there is a tendency for female infidelity to be a far greater social transgression. There are many higher order explanations one could offer, from the controlling arm of the patriarchy to the need for family property to be passed down through the bloodline. But there is a standard Darwinian explanation: those males who were not jealous did not reproduce their genes or values nearly to the same extent as those who were jealous. Motherhood is certain, fatherhood is theoretical (though to a high degree of confidence). Please note that the method of transmission could be cultural.

The moral of the story is that evolution sits atop the engine of replication. Genes/individuals who replicate are successful. The proximate observed diversity of life is due to the scramble to replicate by developing adaptations which maintain the vessel of transmission, the body, long enough for the genes make another copy to recapitulate the process. A focus on macroevolution, with its tendency to highlight morphological change, neglects the reality that the ultimate reason behind this change is the race to replicate. Pathogens do not exhibit gross morphology to the human eye so they are not the exemplars of evolution in the public imagination, but they are superior replicators whose traits are of immense significance to human beings.1

Replication's centrality to evolution should be no great news, The Selfish Gene was written over 25 years ago, and a gene/individual level of selection is the dominant orthodoxy in evolutionary biology. But this is a case where public appreciation is at variance with the established consensus in the field, the diversity of life in all its morphological glory and detail have received more press in the past generation, exemplified by the success of the late Stephen Jay Gould's popularization's of Natural History. One could say that humans have a "sensory bias" toward focusing on vivid morphological diversity rather than the universal algorithm which brings it into being, but this emphasis on the particular over the general tends to result in an inability to extrapolate evolutionary principles to a wider range of circumstances. Ah, the love of butterfly collections....

1 - They kill us, they digest our cellulose, and, they might be responsible for sex.

Posted by razib at 06:27 PM