Thinking about Sex.

[swestrup]

So, I've been trying to form an opinion on why sex evolved anyway. A quick review of the literature shows that there are at least 15 competing theories on the matter. Some facts I have learned are:

• Sexual reproduction is quite "expensive" compared to Asexual methods.
• sex accelerates the rate of gene mixing within a species.
  
• There are MANY species that are asexual, so its clear that sex is not always a winning solution.
• The rise of multicellular life happened not long after sex was invented.
• Many asexual species seem to have remained unchanged from the dawn of life.

Putting all this together, it looks to me like sex is an expensive adaptation that allows a species to track changes in its environmental niche that would otherwise occur too rapidly for asexual adaptation to track. Thus, in those environmental niches that have remained essentially unchanged for the last few billion years, asexual life has a reproductive edge, and dominates. In niches that depend on 'fast' changing events, like the positions of the continents, sexual life if better able to adapt and thrive.

I'm still not sure what this has to do with single- vs multicellular life but it may simply be that most niches that are more easily exploited by multicellular forms are the kind that change too rapdily to be survivable in the long term by asexual forms.

Or am I out to lunch?