A skull unearthed in Greece has been dated to 210,000 years ago, at a time when Europe was occupied by the Neanderthals.
The sensational discovery adds to evidence of an earlier migration of people from Africa that left no trace in the DNA of people alive today.
The findings are published in the journal Nature.
"It's about five times older than any other evidence of modern humans in Europe. And obviously it's older even than Misliya from Israel (a 150,000-year-old early modern human fossil). The shape of the back of the skull is very modern looking and it's potentially the oldest fossil that shows this modern look to the back of the skull," Prof Chris Stringer, from London's Natural History Museum, told BBC News.
The earliest proposed Homo sapiens, a 300,000-year-old skull from Jebel Irhoud in Morocco, does not show this rounded, high back.
The latest evidence was uncovered at the site of Apidima Cave in Greece in the 1970s. Two skulls were found; one was very distorted and the other incomplete, however, and it took computed tomography scanning and uranium-series dating to unravel their secrets.
The more complete skull appears to be a Neanderthal. But the other shows clear characteristics, such as a rounded back to the skull, diagnostic of modern humans.
Modern humans left Africa much earlier
What's more, the Neanderthal skull was younger.
"Now our scenario was that there was an early modern group in Greece by 210,000 years ago, perhaps related to comparable populations in the Levant, but it was subsequently replaced by a Neanderthal population (represented by Apidima 2) by about 170,000 years ago," said Prof Stringer.