Between 400000 – 48000 BC, a human group, later called the Denisovans, lived in Asia. They then interbred with humans expanding from Africa along the coast of South Asia.In 2010 fossil evidence from a Siberian cave in 2008 revealed that their DNA was related to the DNA of people from New Guinea, which contained 4.8% Denisovan DNA.Around 3-5% of the DNA from native people of Papua New Guinea, Australia, Philippines and other nearby islands came from Denisovans, who left Africa as far back as 800,000 BC.In 2014 scientists reported that a genetic between extinct Denisovans and some modern-day Tibetans and Sherpas.

An artist’s interpretation of the hominins that lived near the Sima de los Huesos cave in Spain.Credit…Javier Trueba, Madrid Scientific Films

Scientists have found the oldest DNA evidence yet of humans’ biological history. But instead of neatly clarifying human evolution, the finding is adding new mysteries.

In a paper in the journal Nature, scientists reported Wednesday that they had retrieved ancient human DNA from a fossil dating back about 400,000 years, shattering the previous record of 100,000 years.

The fossil, a thigh bone found in Spain, had previously seemed to many experts to belong to a forerunner of Neanderthals. But its DNA tells a very different story. It most closely resembles DNA from an enigmatic lineage of humans known as Denisovans. Until now, Denisovans were known only from DNA retrieved from 80,000-year-old remains in Siberia, 4,000 miles east of where the new DNA was found.

The mismatch between the anatomical and genetic evidence surprised the scientists, who are now rethinking human evolution over the past few hundred thousand years. It is possible, for example, that there are many extinct human populations that scientists have yet to discover. They might have interbred, swapping DNA. Scientists hope that further studies of extremely ancient human DNA will clarify the mystery.