Genomes from the Neolithic era of East Asia have revealed a missing piece of humankind's prehistory, according to a recent study published in Science on Thursday.
Ancient DNA with modern implications
For scientists, there's much left to learn about genetic history in East Asia. Professor Fu Qiaomei and colleagues from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences found how the movement of populations played a crucial role in the early genetic history of East Asians, according to phys.org.
In the study, the researchers used advanced capture technologies to retrieve ancient DNA from 25 long-deceased people whose remains date back 4,200 years to 9,500 years ago, with one individual's remains dating back only 300 years from northern and southern East Asia.
This newly-sequenced ancient DNA highlights a critical impasse in East Asia's early history: the species-wide transition from hunter-gatherers to agricultural economies.
The 'first layer,' 'second layer' theory of East Asia genomes
One idea about population movement in East Asia suggests that a "second layer" of agriculturalists took the place of an earlier, "first-layer" group of hunter-gatherers in East and Southeast Asia during the Neolithic period.
The genetics of ancient human populations in Siberia, Southeast Asia, and the Japanese archipelago have been well-studied, but little available data was available for the genetics of ancient humans in southern and northern China.
Fu and her colleagues also discovered that this millennia-spanning group of Neolithic humans are the closest genetic relationship to present-day East Asians — close cousins of this "second layer." This means the primary ancestries that comprise the genetic material of East Asian today might have been living in East Asia 9,500 years ago.
Ancient DNA shows modern-day East Asia features
This is significant because, despite genetic ancestries generally more divergent dispersal throughout Southeast Asia and the Japanese archipelago, Neolithic populations were already showing the same genetic features shared by present-day East Asians.
Interestingly, the new finding changed the relationship between present-day East Asians and those living roughly 8,000 years ago, who were previously considered "first-layer" early Asians, according to an earlier theory.
New genome findings don't support "second-layer" theory
On the contrary, Fu and her team found that this specific group of erstwhile-"first-layer" East Asians shares a closer relationship with the "second-layer" East Asians and their modern-day descendants.
This means the current study found no support of a "two-layer" population dispersal model in Neolithic East Asia in this region.
Early Neolithic East Asians were even more genetically differentiated from one another than modern-day East Asians, according to the study. Since 9,500 years ago, a northern ancestry existed along the Yellow River, tracking up into the eastern steppes of Siberia as a distinct population from a southern ancestry that lived along the coast of the southern area of mainland China, in addition to islands in the Taiwan Strait since 8,400 years ago.
The ancient DNA history of the human race represents a vast tapestry of population movement with often surprising dispersal patterns. And in Asia, it seems the remains of those who seem so far away temporally are genetically much closer to modern humans than previously thought.