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Indian-origin scientists find South Asians sharing ancestry with a mysterious population

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Denisovans were probably dark-skinned, unlike the pale Neandertals.n Image source: sci-news.com

New York: Indian-origin scientists among others have found that many bloodlines around the world, particularly of South Asian descent, may actually be a bit more Denisovan- a mysterious population of hominids.

Denisovans lived around the same time as the Neanderthals- researchers including Indian-origin scientists have revealed.

The team from Harvard Medical School and University of California-Los Angeles (UCLA) has created a world map and also used comparative genomics to make predictions about where Denisovan and Neanderthal genes may be impacting modern human biology.

The analysis also proposes that modern humans interbred with Denisovans about 100 generations after their trysts with the Neanderthals.

Denisovan genes can potentially be linked to a more subtle sense of smell in Papua New Guineans and high-altitude adoptions in Tibetans.

Meanwhile, Neanderthal genes found in people around the world most likely contribute to tougher skin and hair.

Most non-Africans possess at least a little bit Neanderthal DNA.

“There are certain classes of genes that modern humans inherited from the archaic humans with whom they interbred, which may have helped the modern humans to adapt to the new environments in which they arrived,” explained senior author David Reich, a geneticist at Harvard Medical School.

On the flip side, there was negative selection to systematically remove ancestry that may have been problematic from modern humans.

“We can document this removal over the 40,000 years since these admixtures occurred,” Reich added.

Reich and lab members, Swapan Mallick and Nick Patterson, teamed up with previous laboratory member Sriram Sankararaman, assistant professor of computer science at the University of California, Los Angeles for the project.

They found evidence that both Denisovan and Neanderthal ancestry has been lost from the X chromosome as well as genes expressed in the male testes.

The team theorises that this has contributed to reduced fertility in males, which is commonly observed in other hybrids between two highly divergent groups of the same species.

The researchers collected their data by comparing known Neanderthal and Denisovan gene sequences across more than 250 genomes from 120 non-African populations publicly available through the Simons Genome Diversity Project.

The analysis was carried out by a machine-learning algorithm that could differentiate between components of both kinds of ancestral DNA, which are more similar to one another than to modern humans.

The study’s limitation is that it relies on the current library of ancient genomes available.

“We can’t use this data to make claims about what the Denisovans or Neanderthals looked like, what they ate, or what kind of diseases they were susceptible to,” said Sankararaman, first author on the paper. “We are still very far from understanding that.”

The new map of archaic ancestry was published in the journal Current Biology. (IANS)

  • Shriya Katoch

    This is really interesting . The idea that South Asians may have a mix of Denisovan with them is fascinating .

Next Story

Cold, Dry Climate Responsible For Neanderthal Disappearance

Cold, Dry Climate Shifts Linked to Neanderthal Disappearance

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Neanderthal
Visitors take pictures of models representing Flores, human and Neanderthal women in the "Musee des Confluences," a new science and anthropology museum in Lyon, central France, Dec. 18, 2014. Neanderthals had a long run in Europe, but disappeared about 40,000 years ago after modern humans showed up. (VOA)

Ancient periods of cold and dry climate helped our species replace Neanderthal in Europe, a study suggests.

Researchers found that such cold periods coincided with an apparent disappearance of our evolutionary cousins in different parts of the continent, and the appearance of our species, Homo sapiens.

“Whether they moved or died out, we can’t tell,” said Michael Staubwasser of the University of Cologne in Germany.

Neanderthals once lived in Europe and Asia but died out about 40,000 years ago, just a few thousand years after our species, Homo sapiens, arrived in Europe. Scientists have long debated what happened, and some have blamed the change in climate. Other proposed explanations have included epidemics and the idea that the newcomers edged out the Neanderthals for resources.

Staubwasser and colleagues reported their findings Monday in the Proceedings of the National Academy of Sciences. They drew on existing climate, archaeological and ecological data and added new indicators of ancient climate from studies of two caves in Romania.

Their study highlighted two cold and dry periods. One began about 44,000 years ago and lasted about 1,000 years. The other began about 40,800 years ago and lasted six centuries. The timing of those events matches the periods when artifacts from Neanderthals disappear and signs of H. sapiens appear in sites within the Danube River valley and in France, they noted.

Neanderthal model
Neanderthal model. Reconstruction of a Neanderthal (Homo neanderthalensis) based on the La Chapelle-aux-Saints fossils. Neanderthals inhabited Europe and western Asia between 230,000 and 29,000 years ago. They did not use complex tools but had mastery of fire and built shelters. It is thought that they had language and a complex social structure, living in small family groups and hunting for food. It is not known why Neanderthals became extinct, but one theory is that they were outcompeted by modern humans (Homo sapiens). Reconstruction by Elisabeth Daynes of the Daynes Studio, Paris, France.

The climate shifts would have replaced forest with shrub-filled grassland, and H. sapiens may have been better adapted to that new environment than the Neanderthals were, so they could move in after Neanderthals disappeared, the researchers wrote.

Katerina Harvati, a Neanderthal expert at the University of Tuebingen in Germany who wasn’t involved in the study, said it’s helpful to have the new climate data from southeastern Europe, a region that H. sapiens is thought to have used to spread through the continent.

But she said it’s unclear whether Neanderthals disappeared and H. sapiensappeared at the times the authors indicate, because the studies they cite rely on limited evidence and are sometimes open to dispute.

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Chris Stringer of the Natural History Museum in London said he thought the paper made a good case for an impact of the climate shifts on Neanderthals, although he believes other factors were also at work in their disappearance.

Rick Potts of the Smithsonian Institution called the study “a refreshing new look” at the species replacement.

“As has been said before, our species didn’t outsmart the Neanderthals,” Potts said in an email. “We simply outsurvived them. The new paper offers much to contemplate about how it occurred.” (VOA)