Environment Egg-celent surprise scrambles scientific consensus

Egg-celent surprise scrambles scientific consensus

Giving birth is beautiful but laying an egg seems a lot simpler. But what if you could choose?

Science has always divided animals into those which produce live babies, like humans, and those which lay eggs, like chickens.

It had to be one or the other, never both. Until now.

The University of Sydney researcher Camilla Whittington was conducting routine observations in the lab when she saw something no one else ever had.

“It’s a very unusual discovery,” she says.

Dr Whittington was investigating an obscure Australian lizard, the three-toed skink, native to several parts of NSW. She already knew it was a little odd.

“The earliest vertebrates were egg-layers, but over thousands of years, developing embryos in some species were held inside the body for longer, until some animals began to give live birth,” Dr Whittington said.

“People mostly think about humans and other mammals giving birth. But there are many species of reptile that give birth, too.”

Three-toed skinks seemed to be among them, or at least the ones that live north of Sydney did.

The strange thing was, those that live around Sydney itself apparently laid eggs.

Still, the skinks more or less obeyed the rule – individuals either laid eggs or produced live babies, depending on where they lived.

Or so it was thought.

“We were studying the genetics of these skinks when we noticed one of the live-bearing females lay three eggs,” Dr Whittington says.

“Several weeks later she gave birth to another baby. Seeing that baby was a very exciting moment!”

It showed for the first time some individual animals can choose, or at least switch between birth modes, possibly to suit varying environmental conditions.

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