In the mountains, Tibetan mastiffs dare to tread where other pups would drop their squeaky toys and whimper with exhaustion. The massive, 150-pound animals thrive at high altitudes, and now researchers know why: the mastiffs have a little extra dose of wolf in their genes.
The big, furry dog breed with a lion-like mane may date back as far as 1,100 B.C., when it began its role as a high-altitude guard dog. Tibetan people have used mastiffs guard their flocks of sheep from predators, like wolves, for centuries. The dogs lived alongside their human companions at altitudes of 15,000 feet or higher, heights in which average dogs wouldn’t withstand the lack of oxygen.