Humans
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Researchers in China have identified a previously unknown northern East Asian lineage of humans that survived the last glacial period – commonly called the last Ice Age – and adapted to life in a warmer climate. The results suggest that, rather than being replaced by farmers during an abrupt cultural shift towards settled lifestyles, these hunter-gatherers persisted and transitioned over a longer period.
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When the last glacial period came to an end, humans had to adapt to a new world. As the frozen tundra was replaced by a lush, arable landscape, our ancestors moved from a nomadic, hunter-gatherer lifestyle to a settled, agricultural one. This period, known as the Palaeolithic-to-Neolithic transition, was a gradual process that began around 12,000 years ago and culminated in fully agricultural societies around 8,000 years ago.
Yet it would be a mistake to think this great transition occurred at the same time for different human populations, or that it evolved in the same way. For instance, we know population shifts occurred in Europe during a major period of warming around 14,000 to 12,900 years ago because of climate fluctuation. As new people migrated into Europe, they brought with them new ideas and tools for farming. In contrast, in south-west Asia, local hunters developed their own agricultural practices and technologies without any significant changes to their population.
But while we know quite a bit about how this period of transition occurred in these two regions, we know a lot less about how it transpired in northern East Asia (where Japan, North and South Korea, China, Mongolia, and the Russian Far East are today). During the Palaeolithic-to-Neolithic transition, this region, with its diverse topography, was beset by a relatively unstable climate. And although there are several archaeological sites with Neolithic characteristics dating to this period, their numbers remain low.
These sites demonstrate distinct features – such as durable dwellings and ground stone tools, and even early millet domestication – which contrasts with those of Late Pleistocene hunter-gatherers. These differences present a muddled cultural profile for this region, with varying degrees of “Neolithization” – or becoming a settled people.
So, what was going on here? The picture suggests a period of gradual transition rather than one where hunter-gatherers were abruptly replaced by more technologically advanced people. But this idea has not been confirmed.
That’s where this new study comes in. The researchers analyzed DNA taken from the Donghulin site near Beijing, which appears to bridge the gap between the last glacial period and the first settled farmers. This site is one of the best representations of the Palaeolithic-to-Neolithic transition because it has a range of Neolithic features, including pottery fragments, durable dwellings and signs of millet domestication. The collective archaeological evidence suggests that different groups of people lived at the site at different times.
“The Donghulin site is a rare yet representative [Palaeolithic-to-Neolithic] site in northern East Asia with a detailed archaeological context, making it an exceptional location for investigating the Neolithic transition period,” the researchers explained in their paper.
They managed to recover and sequence the genomes of two individuals from this site, one was a female identified as DHL_M1, who lived at there around 11,000 years ago (as the last glacial period ended), and the other was a male identified as DHL_M2, who lived during the warmer early Holocene (round 9,500 years ago). In addition, the researchers recovered mitochondrial DNA from a third individual, but this person lacked a clear archaeological context.
The team then compared the genomes of the two individuals with older DNA from individuals who lived during the last glacial period (around 19,000 years ago) and younger DNA from people who lived during the Neolithic period. In addition, the team integrated this DNA data with the archaeological evidence taken from the site.
The results showed that, rather than there being a replacement caused by migrating people – as seen in Europe – DHL_M1 belong to a never-before-seen and much older lineage that had already split from the main northern East Asia population around 19,000 years ago. This suggests that the older Ice Age populations didn’t get wiped out, but persisted in the region for nearly 10,000 years, witnessing the turn towards a warmer climate.
“Our observation indicates some deep [northern East Asia] lineages from the Late Pleistocene persisted through the post-glacial warming period, during cultural shifts toward a more settled lifestyle and wider dietary spectrum,” the team explained.
“This fits the scenario of a prolonged transition for the Neolithization process in northern East Asia, rather than an abrupt replacement.”
According to the results, DHL_M2 did not belong to the same deep, isolated lineage as DHL_M1. Instead, their genetic profile suggested a closer relationship to Neolithic populations in North China, especially the Yumin culture from inner Mongolia. As such, by the time DHL_M2 was alive, new people had moved into the region, eventually replacing the deep lineage of DHL_M1 over a longer period of time.
This finding helped to explain specific differences between the two individuals based on their skull shapes. These differences suggested they belong to two distinct lineages, and now we have the genetic data to explain it. It shows that northern East Asia was more diversly populated than previously thought.
“Although our genetic analysis of the Donghulin site offers a case study for understanding this trajectory, additional samples are required to further elucidate the population history of the [Palaeolithic-to-Neolithic] process in northern East Asia”, the team concluded.
The paper is published in Current Biology.
