The most recent ice age was dominated by gigantic mammals like the mammoth, woolly rhinoceros, and saber-tooth cat. But there's an evolutionary mystery here. How did these animals enter the ice age already perfectly adapted for such brutally cold climates?
The answer lies in the Himalayas rising above present-day Tibet. Paleontologists recently discovered the remains of a woolly rhinoceros dating back some 3.6 million years. That's just about a million years before the beginning of the most recent ice age 2.6 million years ago. The find comprised a complete skull and lower jaw, representing a new species of woolly rhinoceros somewhat more primitive than its later ice age descendants that came to dominate much of Eurasia.
And yet, although it isn't quite the same as its descendants, all the key adaptations that would allow woolly rhinoceroses to thrive during the ice age were already in place. For instance, the skull shows signs of special adaptations that allowed it to clear snow away using its horn. That allowed the ancient rhino to find vegetation hidden underneath the snow and eke out a decent existence in the Tibetan plateaus.
After a few hundred thousand years, the woolly rhinoceros was perfectly adapted for life in Tibet. That proved to be a very useful thing, because it was around that time that the entire world basically became Tibet, as the glaciers descended on Eurasia and the world became choked in ice and snow. While the woolly rhinoceros had evolved during a period where most of the world enjoyed a mild climate, it was poised to thrive in this chilly new order.
The woolly rhinoceros skull was the most dramatic find made in the Tibetan highlands, but it was far from the only one. Evidence of nearly thirty different extinct species were found in the Himalayas, including the three-toed horse, snow leopard, and Tibetan antelope. It appears these creatures all evolved in the generally harsh Tibetan climate and then expanded throughout all Eurasia when the ice age began.
This new find could go a long way to clarifying how megafauna like the woolly rhinoceros - which aren't generally known for their ability to quickly adapt to changing environmental conditions - were able to not just survive but thrive during the chilly Pleistocene era. It's possible that almost all of the giant mammals that dominated Europe and Asia during the ice age had their start in the brutal winters of a relatively small area of the Himalayas. So be sure to respect the local fauna the next time you go hiking - assuming we make it to the next ice age, their giant descendants might well rule the world.
Via Science. Top image by Julie Naylor and fossil composite image by Xiaoming Wang.