February 10, 2009

Dental Determinism

Some interesting evolutionary news: Hox genes, a network linked to the development of teeth, are found in every toothed animal, from ancient jawless fishes to human beings. This set of genes evolved more than 500 million years ago to help primitive chichlids process food; remarkably, the basic genetic development for dental structures remains not only unchanged but is "evolutionarily essential: nature appears never to have made a dentition without it." The paradox of gene mapping and its structural enlightenment is that such startling similarity is unresolved: if humans and chimpanzees share 99.4% of critical DNA sites, what is so peculiar about the remaining six-tenths of a percent that brings human cognizance? Still, this sort of neat evolutionary wormhole brings us that much closer to a complete tree of life, not of the fabled-immortality variety (though an argument could be made that a gene whose function remains the same over half a billion years of life forms is immortal) but the barely-finite permutation of species and their labyrinthian interconnections, an art form that Darwin first understood as instrumental in any understanding of evolution. In yesterday's Times Carl Zimmer writes about the supercomputer's contribution to the development of "supertrees" and the insights they have already bestowed: the German biologist Olaf Bininda-Edmonds published a tree in 2007 connecting all 4,500 known mammals, and claims that his tree suggests that mammals were diversifying well before the extinction of dinosaurs some 65 million years ago. Today the National Science Foundation is working on a project to "reconstruct the evolutionary origins of all living things." Once that's done, it will be interesting to experiment with whether such a diagram can be applied on a particle level, and whether a transposed timeline beginning at the Big Bang will illuminate patterns that were impossible to discern piecemeal. If nothing else, I hope I can trace my lineage back to some fine life-giving algae.

Zimmer is prolific: his most recent book is Microcosm: E. coli and the New Science of Life, but his best is probably Evolution: The Triumph of An Idea.

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