In the latest Science, two biologists from Dartmouth, Bob Cox and Ryan Calsbeek, publish a fascinating study. The female brown anole lizard (anolis sagrei) chooses the largest males it can find to reproduce with. The male offspring have a better chance of surviving if the father is large. However, the size of the father makes no difference in the survival of female offspring. What this study uncovered, is that, if the female can not find a large male and has to make do with a smaller male, she then "chooses" to have female children. The question remaing is, what is the biological mechanism that permits her to choose? How does it work?