Y: The Last Man and Blue Moon Butterflies

A paper in today's issue of Science by Sylvain Charlat and colleagues looks at the evolution of a population of Blue Moon butterflies that was infected with the Wolbachia bacterium, which selectively kills male embryos. The result was a population of butterflies with a female to male ratio of 100:1. When individuals in the population that were resistant to Wolbachia appeared, presumably due to a nuclear mutation, the resistance rapidly spread through the population and within 10 generations the sex ratio was back to 1:1.

PZ Myers compares the Wolbachia-infected Blue Moon butterfly population to the situation in the graphic novel Y: The Last Man, in which all male mammals are killed by a mysterious disease - except the hero Yorick and his monkey.

Substantial parts of it are biologically nearly impossible: the wide cross-species susceptibility, the near instantaneous lethality, and the simultaneity of its effect everywhere (there are also all kinds of weird correlations with other sort of magical putative causes, which may be red herrings).

A disease that infects only males is clearly plausible, but Yorick doesn't follow the example of his butterfly brethren, as PZ points out.

Now here's one thing that bugs me about Y: The Last Man. For this rapid dispersal of resistance to spread, resistant males should be procreating profligately. In the book, Yorick seems to be obstinately abstinent! (Some of the women, at least, understand the principle, and there are plots with attempts to capture the last man for breeding stock for their group.) I can understand how the author might want to resist turning the story into a boring male fantasy of having the only penis among teeming millions of fertile females, but come on, biological reality has to intrude at some point. The future of the human race demands it!

I suppose you have to read the series to find out if Yorick indeed does his part to save humanity.

Tags:Y: The Last Man, sex ratio, Wolbachia, blue moon butterfly