"The Adaptive Significance of Temperature-Dependent Sex Determination in a Reptile" (2008), by Daniel Warner and Richard Shine

In 2008 researchers Daniel Warner and Richard Shine tested the Charnov-Bull model by conducting experiments on the Jacky dragon, (Amphibolurus muricatus) [5] in Australia. Their results showed that temperature-dependent sex determination [6] (TSD) evolved in this species as an adaptation to fluctuating environmental temperatures. The Charnov-Bull model, proposed by Eric Charnov and James Bull in 1977, described the evolution [7] of TSD, although the model was, for many years, untested. Many reptiles and some fish [8] exhibit nongenetic sex determination [6], in which an embryo's environment can influence the sex of the adult organism. Environmental conditions such as humidity or population density can alter sex in some organisms, and a widespread form of non-genetic sex determination [6] is temperaturedependent sex determination [6]. TSD reveals how embryonic development can contribute to the evolution [7] of physiological processes. Researchers have documented TSD in a wide range of species, and they continue to investigate how such a sex determining system has evolved.