Australian lizards on verge of evolutionary leap

QMI Agency

, Last Updated: 3:13 PM ET

Scientists observing a small group of Australian lizards very closely, believe they may be watching evolution happen right before their eyes.

A variety of Australian skink - like snake but with four tiny legs - is slowly starting abandon egg laying and beginning to give birth to live offspring like a mammal does.

Skinks in the mountainous region of New South Wales have almost entirely moved to live birth. But the same species living in the lowlands along the coast are far more likely to lay eggs containing their young.

The subject was discussed in the latest issue of the Journal of Morphology.

According to a 1999 study that looked at the transition that some lizards are known to make from egg-laying to live-birth, the evolutionary step only travels in one direction. Once a species begins giving live births, it never goes back to egg-laying.

Researchers speculate this could be because it's easier to keep offspring protected from the elements and predators if they are inside the mother's body, even if that means a more taxing draw of nutrients and energy from the mother.

Some researchers have suggested the transition from egg-laying to live-birth might not be as difficult as it initially appears.

Some skinks, they argue, simply retain the egg in the uterus for a longer period of time to protect it from colder external temperatures. The longer the egg is kept in the uterus, the thinner the shell becomes. When a skink is born live, all that remains of the shell is a thin membrane, which the mother helps the baby break open.

The cold explanation cites a 1996 study and explains why the mountainous skinks are making the leap to live-birth faster than their lowland counterparts.


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