Jawbone fossil found In Tibet, definitely not like that of humans today.
THE MOUTH OF Baishiya Karst Cave nestles near the base of a towering crag at the edge of the Tibetan Plateau. Strands of colorful prayer flags crisscross the pale face of the hollow, a holy location where Tibetans have long retreated to pray and heal from sickness. Within the cave’s cool confines in 1980, a local monk happened on something unexpected: a jaw with two huge teeth that, while human, was definitely not like that of humans today.
A study published today in Nature reveals just how much this ancient jaw has to say. A detailed analysis of its physical features as well as proteins extracted from the fossil suggest that the mandible, dated to 160,000 years ago, comes from the enigmatic human population known as the Denisovans—a sister group to the Neanderthals previously identified from scant remains found in a single cave in Siberia’s Altai Mountains.
“I just couldn’t believe that at the moment [my colleagues] told me,” says study co-author Dongju Zhang of Lanzhou University, China. “I was really excited.”
Zhang’s excitement is justified: the jawbone, known as the Xiahe mandible after the county in China where it was found, fills a yawning gap in our understanding of this mysterious ancient. While the previous Denisovan fragments come only from the eponymous Denisova Cave in Siberia, people living all across Asia and Australasia today carry Denisovan DNA in their genomes. The discovery of the Xiahe jawbone at a locale over 1,400 miles away from this Siberian cave confirms Denisovans ventured much further across the continent.
It’s thought that after the Denisovans’ ancestors split from their Neanderthal relatives at least 400,000 years ago, they headed east into Asia, while early Neanderthals spread through Europe and western Asia. Modern humans first left Africa some 200,000 years ago, first as a trickle and then in waves. Eventually they encountered and interbred with Neanderthals in the Middle East. Those who trekked east into Asia likewise mated with the resident Denisovans, who left genetic fingerprints still present in Asians today.