Sequenced genome of Altai Mountain Neanderthal has modern human DNA

by SchwerdtfegerK on Avril 9, 2017 - 4:53pm

Kianu Schwerdtfeger

Kristin Muller

Genetics 206

5 March 2017

While it is known that modern humans once coexisted with other species of hominids, such as the Neanderthals and the Denisovans, it is still uncertain how often they may have interacted, or how much they may have even potentially interbred. In a genetic study, published under the name “Ancient gene flow from early modern humans into Eastern Neanderthals,” a team of researchers investigated the genetic makeup of two different prehistoric humans that were found in the Altai Mountains of central Asia, one being a recently discovered species known colloquially as a Denisovan, and the other specimen being a more well-known Neanderthal. Both individuals lived in this region of central Asia about 100,000 years ago.

The genes of the Denisovan were compared to the genes of the Neanderthal. These were then contrasted with the a sequenced 21st chromosome from two European Neanderthals from modern-day Spain and Croatia, respectively. The researchers further compared them with the genes of modern African populations, as those who live in Africa have had the lowest contributions of DNA from other hominids throughout their genetic history. After sequencing, they discovered that the Neanderthal, specifically, had a greater contribution of DNA from modern humans than did the Denisovan or the European Neanderthals, and had specifically inherited modern human alleles dating back to about 100,000 years ago. To elaborate, the genome of the Altai neanderthal shared 5.4% more genetic alleles with modern-day human populations than the Denisovan, 3.5% more than the Spanish Neanderthal, and 4.9% more than the Croatian Neanderthal. As the lineage of modern humans and neanderthals diverged at least 430,000 years ago, this would almost certainly imply that, either the Altai Neanderthal, or a recent ancestor of said Neanderthal, had encountered and interbred with a modern human.

While we known that humans and neanderthals encountered one another, and occasionally mixed (it was estimated by those within this study that modern humans have inherited about 1% of their DNA from Neanderthals on average), we know less about genetic contributions in the other direction. It is not only interesting because it shows what populations of Neanderthals we may have first come into contact with. It also shows where modern humans may have first traveled on their exodus out of Africa, and how we interacted with who and what we encountered.

I always find interest in the historical aspects of our species that have not been conveniently written down for us by our predecessors. The entirety of human history is separated into the written historic accounts and that which we hadn’t recorded, known as “pre-history”. Out of the approximate 200,000 years our species has existed, we only have a few millennia of recorded history that we can study, and what lead up to the transition between hunter-gatherer societies and modern civilization is far harder to determine. It is this enigmatic aspect of our history that I find the most intriguing; whoever existed in prehistoric times never wrote their experiences down for us. Thus, it is up to us to piece together what we can about our own history from the clues our predecessors left behind.