Male or female? In many reptiles sex determination is temperature-dependent. But how this works has been a mystery for 50 years... New insights have emerged from work by Chutian Ge and his collegues who show that ancient conserved epigentic machinary is involved in the thermosensitive regulation of key sex genes. Team Pogona was asked to provide a perspective on the new findings. We have received many enquiries since. In this post, we explain more fully what we believe is going on.