Host-parasite coevolution is like a box of chocolates ... Photo by HAMACHI!.I'm not a particularly big fan of Valentine's Day, but Nothing in Biology Makes Sense! contributor C.J. Jenkins really, really is. She's marking the day with chocolate, red wine, and a new mathematical model explaining the evolution of sex:
There have been a number of different mechanisms of selection that have been proposed to explain sex: host-parasite interactions (Bell 1982), elimination of deleterious alleles (Mueller 1964), and various forms of selection (Charlesworth 1993; Otto and Barton 2001; Roze and Barton 2006). However, none of these alone are able to theoretically overcome the two-fold cost of producing males, so many biologists have started taking a pluralist approach (West et al. 1999; Howard and Lively 1994) and combing one or more of the advantages to being sexual in an effort to understand why the birds do it, the bees do it, and even educated fleas do it.
To learn how a new study revives the longstanding "Red Queen" theory—that sex is beneficial because sexually-produced offspring are more likely to carry genes that can help fight off parasites—go read the whole thing. ◼