Tuesday, August 08, 2006

 

Why Does Sex Exist?

Why does sex exist? A long-popular view holds that sexual reproduction creates new gene combinations that help the next generation resist rapidly co-evolving parasites. Each species constantly changes to achieve the same result - evolutionary advantage - prompting evolutionary biologists to dub this hypothesis the Red Queen (who tells Alice in Through the Looking Glass "it takes all the running you can do, to keep in the same place").

Recent theoretical studies have challenged the generality of the Red Queen hypothesis, suggesting that even though parasites can exert selection pressures that favor sex under some conditions, more often they select against it. They do this, the studies found, by selecting against genes that increase the degree of genetic mixing. And now, Aneil Agrawal has come to the Red Queen's rescue with his own theoretical analysis. While the recent models assumed that host-parasite encounters are random, Agrawal shows that when nonrandom interactions are assumed - so that a host is more likely to acquire parasites from its mother - selective pressures from parasites are much more likely to favor sex.

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The above news report is based on:

Similarity Selection and the Evolution of Sex: Revisiting the Red Queen

John Latter / Jorolat
Evolution Research

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