‘Ghost’ ancestors: African DNA study detects mysterious human species

WASHINGTON (Reuters) - Scientists examining the genomes of West Africans have detected signs that a mysterious extinct human species interbred with our own species tens of thousands of years ago in Africa, the latest evidence of humankind’s complicated genetic ancestry.

The study indicated that present-day West Africans trace a substantial proportion, some 2% to 19%, of their genetic ancestry to an extinct human species - what the researchers called a “ghost population.”

“We estimate interbreeding occurred approximately 43,000 years ago, with large intervals of uncertainty,” said University of California, Los Angeles (UCLA) human genetics and computer science professor Sriram Sankararaman, who led the study published last week in the journal Science Advances.

Homo sapiens first appeared a bit more than 300,000 years ago in Africa and later spread worldwide, encountering other human species in Eurasia that have since gone extinct including the Neanderthals and the lesserknown Denisovans.

Previous genetic research showed that our species interbred with both the Neanderthals and Denisovans, with modern human populations outside of Africa still carrying DNA from both. But while there is an ample fossil record of the Neanderthals and a few fossils of Denisovans, the newly identified “ghost population” is more enigmatic.

Asked what details are known about this population, Sankararaman said, “Not much at this stage.”

“We don’t know where this population might have lived, whether it corresponds to known fossils, and what its ultimate fate was,” Sankararaman added.

Sankararaman said this extinct species seems to have diverged roughly 650,000 years ago from the evolutionary line that led to Homo sapiens, before the evolutionary split between the lineages that led to our species and to the Neanderthals.

The researchers examined genomic data from hundreds of West Africans including the Yoruba people of Nigeria and Benin and the Mende people of Sierra Leone, and then compared that with Neanderthal and Denisovan genomes. They found DNA segments in the West Africans that could best be explained by ancestral interbreeding with an unknown member of the human family tree that led to what is called genetic “introgression.”

WASHINGTON (Reuters) - A new probe built by NASA and the European Space Agency set off on a blazing hot journey to the sun last Sunday to take the first close-up look at the star’s polar regions, in a mission expected to yield insight into how solar radiant energy affects Earth.

The Solar Orbiter spacecraft lifted off from Cape Canaveral, Florida, at 11:03 p.m. ET (0403 GMT Monday), kicking off a 10-year voyage.

“This was picture perfect. And suddenly you really felt you are connected to the rest of the solar system,” Daniel Mueller, a scientist for

It is unclear if West Africans derived any genetic benefits from this long-ago gene flow.

“We are beginning to learn more about the impact of DNA from archaic hominins on human biology,” Sankararaman said, using a term referring to extinct human species. “We now know that both Neanderthal and Denisovan DNA was deleterious in general but there were some genes where this DNA had an adaptive impact. For example, altitude adaptation in Tibetans was likely facilitated by a Denisovan introgressed gene.”

ESA who worked on the mission, said after lift-off. The minivan-sized spacecraft will deploy solar panels and antennas before carrying on toward the sun, a trek assisted by the gravitational forces of Earth and Venus. It eventually will reach as close as 26 million miles from the sun’s surface, or about 72 percent of the distance between the star and Earth.

“I have been in solar physics for many years; I just never thought I would actually witness something come to fruition like this and actually launch. It’s amazing,” said Holly Gilbert of NASA. Solar Orbiter’s primary mission of examining the sun’s polar regions will help researchers understand the origins of solar wind, a soup of charged particles highly concentrated at the two poles, which blast through our solar system, affecting satellites and electronics on Earth. The mission is also expected to glean insight into how astronauts can be protected from radiation in space, which can damage DNA. Solar Orbiter carries 10 instruments packed behind a massive 324-pound (147 kg) heat shield, three of which will peer through tiny windows to survey how the sun’s surface changes over time.