Lizards help us find out which came first: the baby or the egg?

"Have you ever wondered why we give birth to live young rather than lay eggs? Scientists have pondered this for a long time and answers have come from an unlikely source: some of Australia’s lizards and snakes!"

Writes PhD Candidate  Oliver Griffith of the  University of Sydney in The Conversation

"In research published this month in the American Naturalist, my colleagues and I at the University of Sydney studied reptile pregnancy to identify the factors necessary for a placenta to evolve.

"Although most reptiles lay eggs, live birth has evolved many times in the group of reptiles that includes lizards and snakes.

"Some of Australia’s most iconic species, have discarded egg-laying and instead hang onto their babies for the duration of pregnancy and give birth to fully developed young.

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