The Earliest Sex Between Different Human Ancestors May Have Occurred 700,000 Years Ago – ScienceAlert
Our evolutionary history is full of inter-species sex.
Different human ancestor species seem to have mingled and mated far more than anthropologists previously realised. Neanderthals interbred with modern humans. Homo sapiens had sex with Denisovans.
And 700,000 years ago, according to a new study, a population of ancient humans mated with a distinct, unknown population that had separated from other human species at least 1 million years prior.
“This continues the story that we’ve been seeing in studies throughout the past decade: There’s lots more interbreeding between lots of human populations than we were aware of ever before,” Alan Rodgers, an anthropologist and the lead author of the new study, told Business Insider.
“This discovery has pushed the time depth of those interbreedings much farther back.”
According to his team’s research, published today in the journal Science Advances, the newly discovered interbreeding event took place in Eurasia, and it represents the earliest known example of mating between different populations of ancient humans.
The analysis, which compared DNA from Neanderthals, Denisovans, and modern humans from Europe and Africa, lends further credence to the idea that the our ancestors’ genes (and our own) came from myriad sources.
The oldest episode of interbreeding in the anthropological record
Then a 2018 study revealed that Denisovans – which disappeared about 50,000 years ago – passed on some of their genes to Homo sapiens.
But the interbreeding event that Rodgers and his colleagues found was far, far older. In that case, a group of humans who were ancestors of both Neanderthals and Denisovans (the study authors nicknamed them “neandersovans”) interbred with their predecessor species about 744,000 years ago.
Those predecessors, in turn, were part of a”superarchaic” group in Eurasia that was between 20,000 and 50,000 people in size.
A major implication of the study, then, is that human populations migrated from Africa to Eurasia three times during our long evolutionary history: once 1.9 million years ago, again 700,000 years ago, and then a final time 50,000 years ago.
The first of these waves involved the “superarchaics”. Then the neandersovans followed 700,000 years ago; they likely separated from the modern human lineage before they migrated north, the study suggests.
As that second wave of ancestors moved into Eurasia, the researchers wrote, they likely “interbred with indigenous Eurasians, largely replaced them, and separated into eastern and western subpopulations – Denisovans and Neanderthals.”
Then many hundreds of thousands of years later, modern humans left Africa, interbreeding with Neanderthals – and eventually Denisovans, too – as they spread through Eurasia.
“These same events unfolded once again around 50,000 years ago as modern humans expanded out of Africa and into Eurasia, largely replacing the Neanderthals and Denisovans,” the study authors wrote.
A population of ‘superarchaic humans’
Rodgers’ team’s discovery came after they compared publicly available modern human DNA with ancient DNA. The analysis revealed at least four watershed moments in which genetic material passed from one human species to another over the last 1 million years.
Three of those moments matched the results other studies had already found. But the oldest instance was a new find.
In addition to representing the oldest evidence of human interbreeding on record, the finding is also surprising because but the two populations that mated were far less closely related than other human groups previously known to have interbred.
Whereas modern humans and Neanderthals had been on separate branches of the evolutionary tree for about 750,000 years when they interbred, the newly discovered population and the “neandersovans” had been separated for more than 1 million years.
Several mysteries remain, however. Rodgers’ team isn’t sure what ancient species the “superarchaic” population belonged to.
All they know is that genetic evidence suggests the superarchaics separated from our human lineage about 2 million years ago, and that ancient humans were living in Eurasia at the time the species separation occurred.
“We’ve got fossil evidence of humans in Eurasia that dates back to 1.85 million years old,” Rogers said.
At least two groups of human species, or taxa, lived in Eurasia during the time the superarchaics broke off from our lineage. One, Homo erectus, was the first of our ancestors to walk upright. The other possible taxon was Homo erectus’ younger cousin, Homo antecessor, which inhabited modern-day Spain.
“Any of those taxa might be the superarchaics,” Rodgers said. “Or they might be some taxon we don’t know about yet.”
But regardless of which group the superarchaics belonged to, Rodgers said, the new evidence of interbreeding offers a glimpse into an ancient time period that researchers know very little about.
“We’re just shedding light on an interval on human evolutionary history that was previously completely dark,” he said.
This article was originally published by Business Insider.
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University of Alberta scientist to participate in NASA Mars mission – CTV News
Chris Herd might not be going to the Red Planet himself but he’ll play a key role in NASA’s Mars 2020 rover project slated to launch this summer.
Herd, a professor in the Department of Earth and Atmospheric Sciences at the University of Alberta, has been chosen to analyze rock samples collected and stored with the intention of bringing them back to Earth through future missions to Mars.
“It was around the age of 13 that I wanted to work on rocks from Mars,” said Herd. “I wanted to be there when the rocks came back so for me to be chosen to be involved in a big mission and NASA’s next big mission to Mars, and the fact that it’s going to be collecting samples that will eventually come back to Earth, that really is the most exciting thing.”
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Herd is one of 10 experts and the only Canadian selected by NASA for the project.
Earliest interbreeding event between ancient human populations discovered – HeritageDaily
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For three years, anthropologist Alan Rogers has attempted to solve an evolutionary puzzle. His research untangles millions of years of human evolution by analyzing DNA strands from ancient human species known as hominins.
Like many evolutionary geneticists, Rogers compares hominin genomes looking for genetic patterns such as mutations and shared genes. He develops statistical methods that infer the history of ancient human populations.
In 2017, Rogers led a study which found that two lineages of ancient humans, Neanderthals and Denisovans, separated much earlier than previously thought and proposed a bottleneck population size. It caused some controversy–anthropologists Mafessoni and Prüfer argued that their method for analyzing the DNA produced different results. Rogers agreed, but realized that neither method explained the genetic data very well.
“Both of our methods under discussion were missing something, but what?” asked Rogers, professor of anthropology at the University of Utah.
The new study has solved that puzzle and in doing so, it has documented the earliest known interbreeding event between ancient human populations–a group known as the “super-archaics” in Eurasia interbred with a Neanderthal-Denisovan ancestor about 700,000 years ago. The event was between two populations that were more distantly related than any other recorded. The authors also proposed a revised timeline for human migration out of Africa and into Eurasia. The method for analyzing ancient DNA provides a new way to look farther back into the human lineage than ever before.
“We’ve never known about this episode of interbreeding and we’ve never been able to estimate the size of the super-archaic population,” said Rogers, lead author of the study. “We’re just shedding light on an interval on human evolutionary history that was previously completely dark.”
The paper was published on Feb. 20, 2020, in the journal Science Advances.
Out of Africa and interbreeding
Rogers studied the ways in which mutations are shared among modern Africans and Europeans, and ancient Neanderthals and Denisovans. The pattern of sharing implied five episodes of interbreeding, including one that was previously unknown. The newly discovered episode involves interbreeding over 700,000 years ago between a distantly related “super-archaic” population which separated from all other humans around two million years ago, and the ancestors of Neanderthals and Denisovans.
The super-archaic and Neanderthal-Denisovan ancestor populations were more distantly related than any other pair of human populations previously known to interbreed. For example, modern humans and Neanderthals had been separated for about 750,000 years when they interbred. The super-archaics and Neanderthal-Denisovan ancestors were separated for well over a million years.
“These findings about the timing at which interbreeding happened in the human lineage is telling something about how long it takes for reproductive isolation to evolve,” said Rogers.
The authors used other clues in the genomes to estimate when the ancient human populations separated and their effective population size. They estimated the super-archaic separated into its own species about two million years ago. This agrees with human fossil evidence in Eurasia that is 1.85 million years old.
The researchers also proposed there were three waves of human migration into Eurasia. The first was two million years ago when the super-archaics migrated into Eurasia and expanded into a large population. Then 700,000 years ago, Neanderthal-Denisovan ancestors migrated into Eurasia and quickly interbred with the descendants of the super-archaics. Finally, modern humans expanded to Eurasia 50,000 years ago where we know they interbred with other ancient humans, including with the Neanderthals.
“I’ve been working for the last couple of years on this different way of analyzing genetic data to find out about history,” said Rogers. “It’s just gratifying that you come up with a different way of looking at the data and you end up discovering things that people haven’t been able to see with other methods.”
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