Over time, different animals have evolved to survive in different ways. Everything about a species—from its behaviors to its physical traits—has been developed to help the animal adapt to their natural habitat.
So when individual members of a species start to exhibit new behaviors, scientists definitely take note. One creature is changing so drastically that researchers believe they’re watching evolution in action.
Fascinating as it is, these experts have no idea why it’s happening…
This strange creature may look like a snake with extraordinarily tiny arms, but it’s actually the yellow-bellied three-toed skink (or Saiphos equals), and it’s native to eastern Australia. Note the small arms situated just below its face?
For most of its known history on Earth, this type of skink has given birth by laying eggs, but recently scientists have noticed something unusual. This animal’s birthing methods are evolving in real time!
Some yellow-bellied skinks in the warm coastal lowlands are continuing to lay eggs the way they always have. That said, researchers have noticed a major change that’s causing quite a stir in the scientific community…
While the yellow-bellied skinks in the coastal lowlands continue to lay eggs, the same species in the colder mountainous regions are starting to give birth to live young. That means that this type of skink is evolving to a new method of reproduction right before our very eyes.
Throughout history, nearly 100 reptile lineages have transitioned from egg-laying to live births over time. Today, roughly 20 percent of living snakes and lizards give birth to live young. While this transition might’ve been inevitable, no one knew when it would occur.
This was the first time in history that scientists have caught a reptile transitioning from one behavior to the other as it was happening. In the past, no such evolutions were ever recorded in real time, so to speak. So, how did it happen?
James Stewart, a biologist at East Tennessee State University who was researching the phenomenon, said, “By studying differences among populations that are in different stages of this process, you can begin to put together what looks like the transition from one [birth style] to the other.”
One question scientists are hoping to answer in studying the skink’s ability to give birth this way is how the reptile’s live babies are getting nutrients with this new biological arrangement. Are they continuing to receive them from the placenta?
Traditionally, baby mammals acquire nutrients from the placenta, while babies incubated inside eggs absorb their nutrients from the yolk and shell. Without either one of these protective casings, how live skink babies are surviving in vitro is currently a mystery.
Another detail stumping scientists is whether the skinks will begin to favor one type of birth over the other, since both methods carry risks. Eggs are more vulnerable to external threats like weather and predators, but internal fetuses are more dangerous to the mother.
Right now, researchers have more questions than answers, but one thing’s for sure: the science world will definitely be keeping a close watch on the yellow-bellied three-toed skink!
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