The evolutionary utility of gender differences
Anole lizards in the West Indies adapt
rapidly to changing environmental pressures.
There are over 400 identified species
within the Anolis genus. Image from
The Glor Lab at the University of Rochester.Butler, Sawyer, and Losos (2007) suggest that sexual dimorphism -- that is, physical differences between the sexes -- contributes significantly to evolutionary adaptivity, at least in Anolis lizards (see National Geographic for a video of male Anolis lizards attracting a mate). Losos, of Harvard University (boo, Harvard!) in Cambridge, MA (yay, Cambridge!) has been studying evolutionary patterns in these lizards for a couple of years, finding that behavior plays a role in evolution (see Losos, 2006).
One of the issues that I often run into when I'm writing and thinking about Difference Blog is wondering what good gender differences do. They wouldn't exist if their absence wasn't a liability. I hadn't liked any of my explanations.
However, Butler, Sawyer, and Losos's work seems really comforting to me, in a way. If the sexual dimorphism is necessary to ensure broader range of attributes, then diversity of gender expression also feels necessary. For example, if males tend to have longer legs, and shorter legs become a better survival trait, there need to be some males with shorter (e.g. more feminine) legs to pass on this trait. Generally, if I find a piece of science comforting, I assume I'm ignoring or misunderstanding a piece of it. But it's Friday, it's been a rough week, and I'm going to let this one sit for the moment (until one of you points out the hole in my logic, which I hope you will.)