What Makes a Boy Lizard? Genes, Temperature, and Egg Size

In some lizard species, it's not just genetics that determines whether males or females will clamber out of hatching eggs. Some species are also governed by nest temperature, like the the three-lined skink lizard: Seven years ago, Australian biologist Rick Shine showed that low nest temperatures could overrule genetics, and cause embryos to develop into males. Now, Shine and his colleagues have taken their skink research a step farther, showing that the size of an egg's yolk also plays a mysterious role in the ultimate sex of the offspring. Physiologist Rachel Bowden, who was not involved in this research, says the study