Apparently this is a question that has been known to keep some biologists awake at night. (Can’t say I’m one of them; my insomnia is caused by other, equally pressing issues LOL)
Anyway, ERV has written a lovely post looking at this: apparently it’s all to do with metabolic pathways and endogenous retroviruses. Go over there & soak up the goodness 🙂
(And sleep well.)
Grant says:
ERV’s article is now listed as one of the nominees for the Quark Prizes, so you can vote on it if you like.