Lizard Moving From Eggs to Live Birth | National Geographic

A National Geographic news article from a few years ago, but awesomely interesting:

Along the warm coastal lowlands of New South Wales, the yellow-bellied three-toed skink lays eggs to reproduce. But individuals of the same species living in the state’s higher, colder mountains are almost all giving birth to live young.

Evolutionary records show that nearly a hundred reptile lineages have independently made the transition from egg-laying to live birth in the past, and today about 20 percent of all living snakes and lizards give birth to live young only.

So with this particular skink variety, we can see the transition as it’s happening. As the article explains, the transition causes a potential nutrient problem for the baby skinks (less calcium as there’s no egg), but the mother skink’s body solves this already:

“Now we can see that the uterus secretes calcium that becomes incorporated into the embryo—it’s basically the early stages of the evolution of a placenta in reptiles,” Stewart explained.

These observations also show how seemingly complicated transitions in life on earth turn out to in fact be relatively small changes that can be achieved with minor adaptations.

Sometimes, when you [have the opportunity to] look closer, things are actually simpler.