While biologists have been trying to figure out just how prevalent negative epistasis is in nature to test MDH, relatively little attention has been paid to the question of what conditions could lead to the existence of negative epistasis in the first place. If those conditions were known, it would help scientists decide whether it's even worth looking for it or not. Azevedo's study suggests that it is. In many of their simulated worlds, sexual reproduction generated negative epistasis, thus creating the conditions required for its own maintenance. If this is true about the real world, this would constitute a spectacular example of evolution forging its own path.

Although the thought that sex may have evolved as a kind of "genetic waste disposal" mechanism would seem depressing, it gets worse. The evolutionary benefits of sex are likely reaped most effectively by organisms with fast generation times and large population sizes, such as disease-causing microorganisms. That sex also may confer an increased ability to fight back parasites, as proposed by another theory for the evolution of sex, probably serves as little consolation. But it's exactly why scientists, like most other human beings, find sex so intriguing.

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Contact: Lisa Merkl
lkmerkl@uh.edu
713-743-8192
University of Houston
1-Mar-2006