May 24, 2004

Sex - why?

Why are there two sexes?
Imagine a population of hermaphrodites.
1) Some will be genetically biased towards putting more time and effort into mating, their genes will thrive as they inseminate many others.
2) Others will be biased towards expending energy by producing eggs and bearing babies, they will also be genetically successful as can do their best to ensure their children survive.
Those individuals who lie in the middle , and specialise in neither activity, will die out.

The first type leads to a small active gamete, the second a larger, static gamete. The union of two unequal gametes in reproduction is known as anisogamy. Inter-sex competition ensures that this dichotomy persists.

Parker, G.A., R.R. Baker, and V.G.F. Smith. 1972. The origin and evolution of gamete dimorphism and the male-female phenomenon. Journal of Theoretical Biology 36: 529-553.

Why do we have frequent sex?
BBC NEWS | Science/Nature | Famous sex theory questioned
Posted by Martin Sewell at May 24, 2004 12:29 PM | TrackBack