I often hear vague explanations about sex being a way to generate genetic diversity. I don’t find it compelling. If you want genetic diversity, you can do it in much easier ways than turning into a sexually-reproducing dimorphic species. One of them is, just increase the mutation rate, bro.
I think the math is actually pretty clear on this one—sexual selection is an asymptotically more effective optimization algorithm from information theory first principles. If this weren’t true I wouldn’t expect sexually reproductive species to be so dominant, given we evolved from asexual ones.
There happens to be a chapter called “Why have sex?” in MacKay’s *Information Theory* on this topic. In his simplified models, the rate of information gain / good genes discovered per generation is much larger with recombination than without.
Intuitively, mutation in asexual organisms involves randomly changing genes, and if the organism you’re starting from is high-fitness, randomly changing genes is much more likely to be bad than good. So every generation you have to overcome this immense amount of mean regression just to break even. Jacking up the mutation rate makes the problem worse. In sexual selection, you get good genomes basically for free (meaning you can support a much higher mutation rate too!)
That’s not to say asexual reproduction doesn’t work—clearly it does—but it seems to only be viable for small genomes. Past a certain genome size, the asymptotically better scaling of information gain outweighs the constant transaction costs of matching.
I think the math is actually pretty clear on this one—sexual selection is an asymptotically more effective optimization algorithm from information theory first principles. If this weren’t true I wouldn’t expect sexually reproductive species to be so dominant, given we evolved from asexual ones.
There happens to be a chapter called “Why have sex?” in MacKay’s *Information Theory* on this topic. In his simplified models, the rate of information gain / good genes discovered per generation is much larger with recombination than without.
Intuitively, mutation in asexual organisms involves randomly changing genes, and if the organism you’re starting from is high-fitness, randomly changing genes is much more likely to be bad than good. So every generation you have to overcome this immense amount of mean regression just to break even. Jacking up the mutation rate makes the problem worse. In sexual selection, you get good genomes basically for free (meaning you can support a much higher mutation rate too!)
That’s not to say asexual reproduction doesn’t work—clearly it does—but it seems to only be viable for small genomes. Past a certain genome size, the asymptotically better scaling of information gain outweighs the constant transaction costs of matching.
I came here to mention the MacKay :) it’s a great chapter