Lizards re-evolved eggs after thousands of years of live births

It’s an evolutionary U-turn: a group of egg-laying lizards evolved from live-bearing ancestors, which are in turn descended from even older egg-layers


Which came first, the lizard or the egg? In the case of at least one lizard, we have an answer: the live-bearing lizard came first and only later evolved the ability to lay eggs. It’s a rare example of a species re-evolving a complex trait that had been lost.

The common lizard is just that. It is found across a broad swathe of Eurasia, from Ireland in the west to Japan in the east. Its name Zootoca vivipara means “live-bearing” in both Greek and Latin, and as you might expect it gives birth to its young.

But there are exceptions. Two small populations on the edge of the common lizard’s range lay eggs. One of these subspecies is found around the border between Spain and France, and the other in the southern Alps.

Biologists had assumed these subspecies were the last remnants of an egg-laying ancestral

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