5 hours ago
https://www.yahoo.com/news/science/artic...00619.html
EXCERPTS: In a new Science study, scientists read the family tree buried inside modern genomes and turned up "ghost ancestors" in every population on Earth that no fossil records can account for.
Anatomically modern humans are just one branch of a broader family tree. The other branches—the archaic hominins, as scientists call them—include the Neanderthals, who lived across Europe and western Asia, and the Denisovans, who are known mostly from a handful of fossils found in Siberia and Tibet. These archaic lineages interbred with ancient human groups who had migrated out of Africa, which scientists can confirm by comparing rare preserved samples of their DNA with ours.
But did our direct ancestors interbreed with other long-lost hominin lineages before the first major migrations out of Africa roughly 70,000 years ago? Because we have never found any archaic hominin genomes in sub-Saharan Africa, scientists couldn't tell. To get around that limitation, a team of scientists co-led by Yulin Zhang, a computational biologist at the University of California, Berkeley, and geneticist Arjun Biddanda, now at Johns Hopkins University, developed a new method for discovering archaic ancestry using only the DNA of humans from our time.
[...] It found that 2 percent of the DNA in non-African genomes came from archaic lineages, consistent with prior research. Roughly half of that, or 1 percent of the genome, matched sequenced Neanderthals, and a sliver matched Denisovans. The rest, though, ranging from about 0.5 to 1 percent depending on the population, matched nothing anyone has ever sequenced. This "ghost" lineage showed in every population Zhang and her colleagues examined and likely split off from our branch more than 500,000 years ago, around the time that Neanderthals and Denisovans did.
On top of that, the unknown lineage showed up in stretches of DNA that are almost devoid of Neanderthal and Denisovan genes—and which scientists had interpreted as uniquely our own. "When we specifically looked at these regions, they also harbored this ghost ancestry," says Priya Moorjani, a population geneticist at Berkeley and a co-author of the study. "We were really surprised." One of these regions sits around FOXP2, a gene linked to speech.
The results will need to be confirmed with another line of evidence. [...] we could infer that these ghosts formed an equally distant sister group to Denisovans, Neanderthals and possibly modern humans.
"Perhaps these methods really have opened up a new frontier for looking at human evolution," Moorjani says... (MORE - missing details)
EXCERPTS: In a new Science study, scientists read the family tree buried inside modern genomes and turned up "ghost ancestors" in every population on Earth that no fossil records can account for.
Anatomically modern humans are just one branch of a broader family tree. The other branches—the archaic hominins, as scientists call them—include the Neanderthals, who lived across Europe and western Asia, and the Denisovans, who are known mostly from a handful of fossils found in Siberia and Tibet. These archaic lineages interbred with ancient human groups who had migrated out of Africa, which scientists can confirm by comparing rare preserved samples of their DNA with ours.
But did our direct ancestors interbreed with other long-lost hominin lineages before the first major migrations out of Africa roughly 70,000 years ago? Because we have never found any archaic hominin genomes in sub-Saharan Africa, scientists couldn't tell. To get around that limitation, a team of scientists co-led by Yulin Zhang, a computational biologist at the University of California, Berkeley, and geneticist Arjun Biddanda, now at Johns Hopkins University, developed a new method for discovering archaic ancestry using only the DNA of humans from our time.
[...] It found that 2 percent of the DNA in non-African genomes came from archaic lineages, consistent with prior research. Roughly half of that, or 1 percent of the genome, matched sequenced Neanderthals, and a sliver matched Denisovans. The rest, though, ranging from about 0.5 to 1 percent depending on the population, matched nothing anyone has ever sequenced. This "ghost" lineage showed in every population Zhang and her colleagues examined and likely split off from our branch more than 500,000 years ago, around the time that Neanderthals and Denisovans did.
On top of that, the unknown lineage showed up in stretches of DNA that are almost devoid of Neanderthal and Denisovan genes—and which scientists had interpreted as uniquely our own. "When we specifically looked at these regions, they also harbored this ghost ancestry," says Priya Moorjani, a population geneticist at Berkeley and a co-author of the study. "We were really surprised." One of these regions sits around FOXP2, a gene linked to speech.
The results will need to be confirmed with another line of evidence. [...] we could infer that these ghosts formed an equally distant sister group to Denisovans, Neanderthals and possibly modern humans.
"Perhaps these methods really have opened up a new frontier for looking at human evolution," Moorjani says... (MORE - missing details)