Studies of DNA from peoples who lived during the last Ice Age, or shortly after, are helping us understand the origins of modern population groupings, and how we relate to archaic humans.

A review of these finds, published in Trends in Genetics, reveals that around 40,000 years ago Europe and Siberia were populated by at least two peoples who have left no genetic trace among modern populations. They can, however, help us understand our connection to the Neanderthals.

The period 45-35,000 years ago is known in anthropology, somewhat contradictorily, as “Ancient Modern A” (AMA). Fossils from this period, particularly those from which we can extract DNA, are rare.

Two such finds, known as Kostenki 14 from western Siberia and Goyet Q116-1 from Belgium, have genetic signatures that show them to have been more closely related to modern Europeans, than to the populations of India or China. A third, known as the Tianyuan individual, found near Beijing, bears a genetic resemblance to modern East Asian populations. In combination, these finds confirm the genetic differences between the peoples who became the inhabitants of Europe and East Asia existed 40,000 years ago.

However, the oldest completely sequenced human, Ust'-Ishim from Central Siberia, and Oase 1 from Romania, were genetically no closer to recent inhabitants of these regions than to those from other parts of Eurasia. The Chinese Academy of Science's Dr Melinda Yang and Professor Qiaomei Fu argue in the article these two discoveries provide; “Growing evidence that some populations in Eurasia during the AMA did not contribute substantial ancestry to present-day populations.”

What happened to these genetically distinct populations we can only guess, but having found representatives of two of them, it seems likely there were others who did not survive the Ice Age.

Importantly, these finds date from a time when Neanderthals were still alive. Like modern Eurasians, Ust'-Ishim carried distinctively Neanderthal DNA. These sequences are less dispersed through the genome than in our own, an indication of more recent interbreeding.

This helps narrow down the timing of the most significant interbreeding between modern Homo Sapiens and Neanderthal to 95-105,000 years ago. On the other hand, the Oase 1 specimen appears to be only 4-6 generations from a separate case of inbreeding, one that had little or no impact on the genomes of people today.

Comparison between these five specimens shows the Goyet and Tianyuan individuals, while both genetically connected to current populations in their region, also had more in common with each other than might be expected, suggesting that even at the time, when all movement was by foot, there was some gene flow between peoples in Europe and the eastern end of Asia, something that increased greatly thousands of years later after the domestication of the horse.