It has shown rapid shifts in ancestry over the last 10,000 years across Asia, likely due to migration and cultural exchange
The very first human beings originally emerged in Africa before spreading across Eurasia about 60,000 years ago. After that, the story of humankind heads down many different paths, some more well-studied than others.
Eastern regions of Eurasia are home to approximately 2.3 billion people today — roughly 30 per cent of the world’s population. Archaeologists know from fossils and artifacts that modern humans have occupied Southeast Asia for 60,000 years and East Asia for 40,000 years.
But there’s a lot left to untangle. Who were the people who first came to these regions and eventually developed agriculture? Where did different populations come from? Which groups ended up predominant and which died out?
Ancient DNA is helping to answer some of these questions. By sequencing the genomes of people who lived many millennia ago, scientists like me are starting to fill in the picture of how Asia was populated.
In 2016, I joined Qiaomei Fu’s Molecular Paleontology Lab at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences in Beijing. Our challenge: Resolve the history of humans in East Asia, with the help of collaborators who were long dead — ancient humans who lived up to tens of thousands of years ago in the region.
Members of the lab extracted and sequenced ancient DNA using human remains from archaeological sites. Then, Fu and I used computational genomic tools to assess how their DNA related to that of previously sequenced ancient and present-day humans.
One of our sequences came from ancient DNA extracted from the leg bones of the Tianyuan Man, a 40,000-year-old individual discovered near a famous paleoanthropological site in western Beijing. One of the earliest modern humans found in East Asia, his genetic sequence marks him as an early ancestor of today’s Asians and Native Americans. That he lived where China’s current capital stands indicates that the ancestors of today’s Asians began placing roots in East Asia as early as 40,000 years ago.
Farther south, two 8,000- to 4,000-year-old Southeast Asian hunter-gatherers from Laos and Malaysia associated with the Hòabìnhian culture have DNA that, like the Tianyuan Man, shows they’re early ancestors of Asians and Native Americans. These two came from a completely different lineage than the Tianyuan Man, which suggested that many genetically distinct populations occupied Asia in the past.
But no humans today share the same genetic makeup as either Hòabìnhians or the Tianyuan Man, in both East and Southeast Asia. Why did ancestries that persisted for so long vanish from the gene pool of people alive now? Ancient farmers carry the key to that answer.
DNA carries marks of ancient migrations
Based on plant remains found at archaeological sites, scientists know that people domesticated millet in northern China’s Yellow River region about 10,000 years ago. Around the same time, people in southern China’s Yangtze River region domesticated rice.
Unlike in Europe, plant domestication began locally and was not introduced from elsewhere. The process took thousands of years, and societies in East Asia grew increasingly complex, with the rise of the first dynasties around 4,000 years ago.
That’s also when rice cultivation appears to have spread from its origins to areas farther south, including lands that are today’s Southeast Asian countries. DNA helps tell the story. When rice farmers from southern China expanded southward, they introduced not only their farming technology but also their genetics to local populations of Southeast Asian hunter-gatherers.
The overpowering influx of their DNA ended up swamping the local gene pool. Today, little trace of hunter-gatherer ancestry remains in the genes of people who live in Southeast Asia.
Farther north, a similar story played out. Ancient Siberian hunter-gatherers show little relationship with East Asians today, but later Siberian farmers are closely related to today’s East Asians. Farmers from northern China moved northward into Siberia bringing their DNA with them, leading to a sharp decrease in prevalence of the previous local hunter-gatherer ancestry.
Genetically speaking, today’s East Asians are not very different from each other. A lot of DNA is needed to start genetically distinguishing between people with different cultural histories.
What surprised Fu and me was how different the DNA of various ancient populations were in China. We and others found shared DNA across the Yellow River region, a place important to the development of Chinese civilisation. This shared DNA represents a northern East Asian ancestry, distinct from a southern East Asian ancestry we found in coastal southern China.
When we analysed the DNA of people who lived in coastal southern China 9,000-8,500 years ago, we realised that already by then much of China shared a common heritage. Because their archaeology and morphology was different from that of the Yellow River farmers, we had thought these coastal people might come from a lineage not closely related to those first agricultural East Asians. Maybe this group’s ancestry would be similar to the Tianyuan Man or Hòabìnhians.
But instead, every person we sampled was closely related to present-day East Asians. That means that by 9,000 years ago, DNA common to all present-day East Asians was widespread across China.
Today’s northern and southern Chinese populations share more in common with ancient Yellow River populations than with ancient coastal southern Chinese. Thus, early Yellow River farmers migrated both north and south, contributing to the gene pool of humans across East and Southeast Asia.
The coastal southern Chinese ancestry did not vanish, though. It persisted in small amounts and did increase in northern China’s Yellow River region over time. The influence of ancient southern East Asians is low on the mainland, but they had a huge impact elsewhere. On islands spanning from the Taiwan Strait to Polynesia live the Austronesians, best known for their seafaring. They possess the highest amount of southern East Asian ancestry today, highlighting their ancestry’s roots in coastal southern China.
Other emerging genetic patterns show connections between Tibetans and ancient individuals from Mongolia and northern China, raising questions about the peopling of the Tibetan Plateau.
Ancient DNA reveals rapid shifts in ancestry over the last 10,000 years across Asia, likely due to migration and cultural exchange. Until more ancient human DNA is retrieved, scientists can only speculate as to exactly who, genetically speaking, lived in East Asia prior to that.
[Understand new developments in science, health and technology, each week. Subscribe to The Conversation’s science newsletter.]
Melinda A. Yang, Assistant Professor of Biology, University of Richmond
This article is republished from The Conversation under a Creative Commons license. Read the original article.
We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.