Hot Wild Dragons Set Sex Through Temperature Not Genes

At room temperature, a bearded dragon’s sex depends on two chromosomes. If they have two Z chromosomes, these lizards develop as males. Those with a Z and a W become females. But raise the thermostat up a few notches, and something different happens. If a clutch of dragon eggs are incubated at 34 degrees Celsius, their bodies ignore the usual instructions from their sex chromosomes. Even if half of them are genetically male (ZZ), all of them will hatch as females.

Clare Holleley from the University of Canberra found some of these “sex-reversed” ZZ females in the wild, and bred them with the usual ZZ males. All the ...

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