Ancient DNA Sheds Light on Early Human History

n honor of the 20th anniversary of human genome sequencing completion, a research team led by scientists at the Chinese Academy of Sciences reviewed the most recent progress in the field of ancient DNA (aDNA), i.e., DNA obtained from the remains of past organisms.  This review was published in Science. 

Ancient DNA research began with short DNA fragments and subsequently advanced due to the broad application of high-throughput sequencing (HTS) techniques. In 2010, the publication of three draft ancient genomes (i.e., Neanderthal, Denisovan, and a 4-thousand-year (kyr)-old modern human from Greenland) marked a new era for aDNA research.  The genomes of extinct archaic humans (i.e., Neanderthals and Denisovans) have been reconstructed. Importantly, the Denisovans were first identified by using only aDNA data. These two archaic lineages were shown to have separated from modern humans ~550 thousand years ago (ka). They subsequently separated from each other ~400 ka. 

As for early modern human populations, genetic data support an origin in Africa. However, it remains difficult to determine a single model for characterizing the origin of African ancestry. In any case, sometime between ~250–200 ka, five major branches contributing to early modern human ancestry started to split from each other within a short time in Africa. 

In Eurasia, genomic data have been obtained from early modern humans dating to as early as ~45 ka. Some of them show no detectable genetic continuity with later populations, while others, including those representing Ancient North Siberians, Ancient Europeans, and Ancient Asians, may be genetically connected with present-day human populations. Over time, increasing population structure, greater population interaction and higher migration occurred across Eurasia.