Freethought & Rationalism Archive

ps418 · 03-24-2003, 10:17 AM

Two interesting articles in the most recent issue of PNAS . The first article (Gilad et al., 2003) provides evidence for greatly reduced selective pressure on human olfactory receptor genes. Far more OR genes have been mutated to pseudogenes (~60%) in humans than in mice or other primates (~20% in mice).

The second article (Liman and Innan, 2003) shows that the vomeronasal organ [which is probably nonfunctional for pheremone transduction in humans, because a gene required for its function in mice TRPC2, is a pseduogene in humans] probably became nonfunctional fairly early in primate evolution, before the divergence of apes and Old World monkies.

Quote:

Because TRPC2 is expressed only in the VNO, the loss of selective pressure on this gene can serve as a molecular marker for the time at which the VNO became vestigial. By analyzing sequence data from the TRPC2 gene of 15 extant primate species, we provide evidence that the VNO was most likely functional in the common ancestor of New World monkeys and Old World monkeys and apes, but then became vestigial in the common ancestor of Old World monkeys and apes. We propose that, at this point in evolution, other modalities, notably the development of color vision, may have largely replaced signaling by pheromones.

Yoav Gilad, Orna Man, Svante P��bo, and Doron Lancet
Human specific loss of olfactory receptor genes. PNAS 2003 100: 3324-3327

Emily R. Liman and Hideki Innan. Relaxed selective pressure on an essential component of pheromone transduction in primate evolution. PNAS 2003 100: 3328-3332.

Patrick

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