Why do kangaroos have 3 vaginas?

Kangaroos are pretty peculiar on the outside: They’re the world’s largest marsupials, they hop to get around, and they use their tails as a fifth limb. But they’re also pretty unusual on the inside: Female kangaroos have two vaginas — or three, if they’ve given birth. Why could that be?

The most likely explanation is that it’s an adaptation to Australia’s unforgiving environment. Multiple vaginas — and uteruses, of which they also have two — enable female kangaroos, and all marsupials, to have multiple offspring at different stages of development at any given time. That helps increase the chances of one surviving to adulthood.