And What Sex Will Your Baby Be?

In mammals and birds, the sex of the offspring is determined genetically: If the male mammal passes on its X chromosome, the offspring will be female; if it passes on its Y chromosome, the offspring will be male. In birds, the female passes on either her W chromosome (female offspring) or her Z chromosome (male offspring). However, in many reptile species, it is not genes that play a role in sex determination, but actually the weather – and thus meanwhile also climate change.