Researchers at deCODE genetics and fellow collaborators from the Max Planck Institute and universities in Denmark and Iceland have published the first study to use a whole genome sequence data from across a population in order to analyze the current succession of interbreeding modern and ancient humans over 50,000 years ago.
The paper was published in the renowned journal Nature and supports prior evaluations that most people outside of Africa have about two percent old ancestry, mainly based on the outcome of repeated contact and interbreeding between different groups of Homo sapiens and various Neanderthals.
The results also depict genomic sequences from Denisovans, which are more important than previously expected – another ancient human species that hybridized with both Neanderthal and Homo sapiens.
However, the meaning of this research is found in the unique magnitude of information that was utilized in order to understand the nature and effect of this ancient legacy. In its first place, the paper used whole genome sequence (WGS) data from 28,000 Icelanders, about ten percent of the population, and 286 sub-Saharan Africans in the 1,000 Genomes project.
Five Archaic Variants
A restricting factor in prior research has been the excessive dependence on searching modern genomes for chain fragments coming from just three ancient individuals from whom there is decent quality sequence data, namely two Neanderthals and one Denisovan.
The team of researchers turn this estimation around, using the African sequences as a baseline for Homo sapiens with no admission from Neanderthals, and against which they compared the Icelandic data. The resulting chromosomal segments found in Icelanders but not shared by Africans compose a large collection of 15 million presumed ancient fragments.
After merging identical and overlapping segments, the scientists detected over 50,000 distinct ancient fragments covering about 38 to 48 percent of the readable genome. These had almost 400,000 single-letter sequence versions that are not found in the African samples. After examining the archaic variants, the team detected five ancient versions with genome-wide crucial associations.
“Whether individually or collectively, our genome enables us to learn more about who we are by telling us where we come from. This paper is a kind of ancestry report for one branch of our species, and it’s telling us that in this particular neighborhood we are not just Homo sapiens but also the descendants of ancient archaic humans – cousin species whose lineage is thus not entirely extinct,” said Kari Stefansson, CEO of deCODE and a senior author on the study.