Now, using new technology, scientists have sequenced with high precision the genome of one of those close but little-known relatives: an extinct people known as the Denisovans, who lived in and around modern-day Siberia.
The Denisovan genome, reported online Thursday in the journal Science, was derived from tiny quantities of shredded DNA extracted from a finger bone found in a Russian cave in 2008, as well as a tooth found later.
What is striking, scientists said, is that it is every bit as detailed as a sequence generated with a fresh blood or saliva sample from someone alive today.
Analysis of the genome and comparisons with ours and the Neanderthals' will offer insights into the history of Homo sapiens — who we mated with, where and when — as well as the unique genetic changes that make modern humans who they are, scientists said.
The new genome gives scientists a sense of just how much of our genomes we owe to our extinct relatives. About 3% to 5% of the DNA in people native to Papua New Guinea, Australia, the Philippines and other islands nearby came from Denisovans, the study found, confirming reports based on a draft version of the Denisovan genome. The authors of the study didn't find any significant contribution of Denisovans to the DNA of people from mainland Eurasia, however.
The new gene-sequencing techniques also allowed scientists to more precisely calculate how much of modern humans' DNA came not from Denisovans but Neanderthals. They found, to their puzzlement, that Native Americans and people in East Asia have more Neanderthal DNA than do people whose ancestors are from Europe, where most Neanderthals lived."