There were many different types of hominids and human species throughout our history. We live with dozens of them over millions of years. For the most part, we mixed with them or killed them all 30,000 years ago .
A new study published in PNAS thus suggests that Denisovans and Tibetans interbred about 49,000 years ago, giving Tibetans the EPAS1 gene. This gene was not activated until 9,000 ago, which later gave Tibetans the beneficial adaptation to living in high-altitude areas, including regulating oxygenation in the blood .
History of our lineage
At the moment, there is some consensus in admitting this summary history : 7 million years ago the hominid lineage began, 4 million years ago Australopithechus appeared, the genus Homo arose from these ancestors and, 1.8 million years ago, it began to leave Africa for the rest of the world. About 60,000 years ago, a group of modern humans came across populations of Neanderthals that had lived in Europe and parts of Asia for a quarter of a million years.
In 2008, however, another protagonist was added to the story: the Denisovans . Thanks to the findings of a handful of bones in the Siberian cave of Denisova and the latest technology in genetic sequencing, we must now add them to this genetic Game of Thrones, since part of their genome has lasted among some Melanesians (up to 5% of the genetic material among some inhabitants of the island of Nueva Guinea). It is still reckless to talk about Denisovans, because everything we know about them comes from one enclave and has been processed by a single laboratory, but their existence forces us to re-evaluate where we come from, who we mix with.
At the moment, studies of the Denisova remains are continuing. Our greatest exponent today is a girl named Denny, who was presumably conceived 90,000 years ago by a Neanderthal female and a Denisovan male . The girl had brown hair and eyes and dark skin, and genetic information reveals that she was more like Neanderthals than modern humans.
For the moment, thanks to this new species, we can begin to better understand some adaptations to the environment typical of superheroes. Like the fact that Tibetans are so well adapted to heights . Tibetans live in a region that is, on average, more than 4,000 meters above sea level. At this point, oxygen is scarce, and taking a step means panting, exhausting yourself and even feeling dizzy or light-headed. However, Tibetans pilgrimage at more than 4,000 meters, prostrating at each step, showing none of these signs.
This genetic inheritance, which has been found by researchers by sequencing the DNA of a group of Tibetans, ls it would allow to regulate oxygenation in the blood . The most surprising thing is that this trait is not found in Homo sapiens, only in Denisovans.
For people whose ancestors lived at lower altitudes, this genetic uniqueness raises the possibility of heart problems in the short term, and is useless for reproduction, as it increases the risk of pre-eclampsia (hypertension during pregnancy). But at high altitudes, this uniqueness does pay off : you have greater fitness and fertility, even when there’s little to breathe. The genetic basis for the inherited adaptation of the Denisova hominid by Tibetans involves a protein called EPAS1, which controls oxygen regulation. The EPAS1 gene is known as the gene for hypoxia, because its mutations are associated with differences in the concentration of hemoglobin in the blood.