India and China's plates smashed into each other 55 million years ago, and this collision ultimately created the Himalayas, home to the world's biggest mountains..but we weren't exactly sure when this part happened. Now, thanks to frog genes, we know.
Huge mountain ranges are probably the most dramatic proof of plate tectonics, as colliding plates send unimaginable amount of rock shooting straight up into the sky. Home to the world's biggest mountain in Mount Everest (not to mention the world's toughest, K-2), the Himalayas are an indelible reminder of Earth's shifting landmass. But as much as geologists long ago figure out the "why" and the "how" of the Himalayas's formation, determining the "when" has proven trickier.
Now, evolutionary biologists have stepped in to help out, building a timeline of the formation of the Himalayas from the divergent evolution of frog species caught on either side of the growing mountains. UC-Berkeley biologist David Wake explains:
"Geologists know a lot about that area, but what they haven't been able to do is give a sequence to the timing of the rise of particular mountain masses and particular ridges and pieces. We use these frogs as a surrogate for a time machine. What we have here is a group of very old frogs that are so fixed to their habitats that they just stuck there, sitting on that mountain mass when it got raised up. They were separated by these uplifts and by the rivers between the mountains into different units, and these give us a fix on the timing of geological events."
The biologists discovered species of frogs split apart at four different intervals tied to new geological activity in the Himalayas, at 27, 23, 19, and 9 million years ago. These long breaks between speciation adds credence to an alternative, less-accepted geological theory that the Himalayas formed in sharp bursts instead of continuously.
The frogs had been overlooked as a potential guide because all the species that live around the mountains today share two fundamental characteristics that allow them to survive in such a harsh, steep environment: unusually strong arms and spines. It was only when Dr. Wake and his colleagues examined the frogs that they were able to demonstrate these features were not the result of one evolution 50 million years ago, but rather a case of the different, isolate species finding similar but separate solutions to the challenge of living in the shadow of Everest.