A Complex Family Heritage

Exactly what species the ‘Ghost people’ belonged to is unknown, but humans mated with them around 50,000 years ago, researchers discovered. The ancient species split from the common ancestor of humans, Neanderthals and Denisovans more than half a million years ago
Image Source

The discovery of a new ancient human ancestor is still in its primitive stages.

But early indicators hint that the ghost population shared a common ancestor with Neanderthals, modern humans and Denisovans around a million years ago.

And at some point, up until around 360,000 years ago, it branched off to become its own species.

This group then later bred with the ancestors of modern west Africans around 50,000 years ago, according to the study. __ Source

The DNA of 405 West Africans was examined for “unusual” DNA by a pair of UCLA scientists. The researchers discovered a significant component of “archaic human” DNA not seen before.

The unusual DNA found in West Africa isn’t associated with either Neanderthals or Denisovans. Sankararaman and his study co-author, Arun Durvasula, think it comes from a yet-to-be-discovered group.

“We don’t have a clear identity for this archaic group,” Sankararaman says. “That’s why we use the term ‘ghost.’ It doesn’t seem to be particularly closely related to the groups from which we have genome sequences from.”

The scientists think the interbreeding happened about 50,000 years ago, roughly the same time that Neanderthals were breeding with modern humans elsewhere in the world. It’s not clear whether there was a single interbreeding “event,” though, or whether it happened over an extended period of time. __ Source

The evolutionary origins of modern humans cannot be told completely, and can certainly not be told accurately as a simple story. The data simply is not in. But scientists continue to look for the missing pieces. The use of modern DNA sequencing technology along with modern statistical and informatics allows for a more careful sleuthing of origins.

The standard story has long been that all humans have the same DNA. We have been told authoritatively many times that every branch of the human tree evolved slowly — and in a very limited fashion — from a common stock located in Africa. The recent news that out-of-Africa humans cross-bred with Neanderthal and Denisovans was something of a shock. The knowledge that many of those left behind in Africa bred with archaic humans suggests a greater genetic diversity than anyone had ever suspected.

The new study jibes with previous research, which also suggests the presence of “ghost” hominins in the genetic material of modern-day Africans. In a 2017 study, researchers examined the saliva of people from sub-Saharan Africa, finding that the sample carried genetic evidence of an as-yet-unknown ancestor.

When that study was released, lead author Omer Gokcumen told Inverse that the findings were proof that Homo sapiens “absorbed different populations that lived around us.”

Human history, he said, is not “as simple as we previously thought.”

__ Source

One Hypothetical and Oversimplified Timeline of Human Development

One million years ago – Homo sapiens (modern humans), Denisovans, Neanderthals and an unidentified ‘ghost’ populations had not yet evolved. All that existed was a single common ancestor. [Ed.: Unlikely]

500,000 to 360,000 years ago – ‘Ghost people’ split off and formed its own species.

700,000 to 300,000 years ago – Neanderthals split from the common ancestor to form its own species and migrated to Western Eurasia [Ed.: Homo erectus and others also migrated out of Africa, as early as 2 million years ago]

765,000 to 550,00 years ago – Denisovans split and formed its own species and dominated Eastern Eurasia

130,000 years ago – Common ancestors in Africa evolved into what we recognise today as Homo sapiens

100,000 years ago – A large wave of Homo sapiens migrated out of Africa [Ed.: There were multiple waves beginning well before 100,000 years ago]

75,000 years ago – Neanderthals branched westwards and encountered deniovans. These two species subsequently mated.

50,000 years ago – Parts of the Homo sapiens population leaving Africa mated with Neanderthals

50,000 years ago – ‘Ghost’ people species in Africa interbred with Homo sapiens in Africa

50,000 years ago – Denisovans and Neanderthals were mating with Homo sapiens, albeit in Asia and Europe respectively.

40,000 years ago – Denisovans and neanderthals went extinct [Closer to 30,000 years ago]

30,000 years ago – European and East Asian Homo sapiens populations split

Some Europeans then migrated back into Africa where they mated with native Africans

15,000 years ago – Homo sapiens migrated into the Americas

Source

Wikipedia (Denisovan)

It will take some time to collect and make sense of the data. But as a species it is time that we grow up, and acknowledge that we are a lot more genetically interesting and diverse than our politically correct overlords have been telling us. Of course if not for the internet it would be easier to keep all scientific research about human biodiversity quiet.

Research article in 12 Feb 2020 Science Advances by authors Arun Durvasula and Sriram Sankararaman

It is difficult to keep it all politically correct, but here is one of the theories:

By 100,000 years ago, humans had dispersed and diversified into at least three species. Our own species, Homo sapiens, lived in Africa and the Middle East, Homo neanderthalensis lived in Europe, and Homo floresiensis in southern Asia. DNA from human remains in Denisova cave, Russia, suggest a probable fourth species was also still extant when Homo sapiens was migrating through southern Asia about 60,000 years ago. Modern Melanesians have about 4% of this DNA. The species is unknown, but may be late surviving Homo heidelbergensis or a yet-to-be-discovered species. This diversity disappeared about 28,000 years ago, however, and only one human species now survives. __ https://australianmuseum.net.au/learn/science/human-evolution/the-first-migrations-out-of-africa/

But if there are no barriers to cross-breeding between the different branches of human descent, what constitutes a “human species?”

Update: The plot grows thicker

According to the newest analysis, published this week in the journal Science Advances, the Neanderthal-Denisovan ancestor interbred with a separate hominin group, dubbed super-archaics, some 700,000 years ago.

“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 new study. “We’re just shedding light on an interval on human evolutionary history that was previously completely dark.”

This entry was posted in Africa, anthropology, Genetics and Gene Expression and tagged . Bookmark the permalink.

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