ANCIENT humans migrated from Africa in three different waves – and interbred across species as far back as 700,000 years ago.
That's according to a new study that reveals how the earliest humans moved into Eurasia.
Three main groups are believed to have moved north from Africa into Eurasia.
One is called the Super-Archaics, a mysterious group that left Africa around 2million years ago.
Next came the ancestors of the Neanderthals and the Denisovans, who left 700,000 years ago – and bred with the Super-Archaics.
Finally, modern humans migrated north 50,000 years ago, and interbred with several human species.
According to the new study, the interbreeding between the Super-Archaics and the Neanderthal-Denisovan ancestors is particularly special.
The two populations were more distantly related than any other in human history, they say.
"We've never known about this episode of interbreeding," said anthropologist Alan Rogers, of the University of Utah.
"And we've never been able to estimate the size of the super-archaic population.
"We're just shedding light on an interval on human evolutionary history that was previously completely dark."
To make the discovery, Rogers and his co-authors studied how mutations are shared among modern Africans and Europeans.
And the same was done for ancient Neanderthals and Denisovans.
They found evidence of five episodes of interbreeding, including one that was previously unknown.
Super-Archaics interbreeding with Neanderthal-Denisovan ancestors were very distantly related.
Modern humans and Neanderthals were only separated for 750,000 years when they interbred.
But this earlier interbreeding event involved groups that 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.
Who were the Neanderthals? Our mysterious extinct cousins explained
Here's what you need to know…
- The Neanderthals were a mysterious human ancestor who died out around 40,000 years ago.
- Thousands of their tools, weapons and other artefacts have been found, as well as several nearly complete skeletons.
- Neanderthals were the original 'cave men', thought for decades to be brutish and dim-witted compared to humans.
- However, a growing body of evidence suggests we've been selling Neanderthals short.
- Their brains were bigger than ours and they indulged in cultural activities like cave painting and body art.
- Our heavy-browed cousins even had funerary rituals, meaning they buried their dead with an afterlife in mind.
- Having lived in Africa for many millennia, Neanderthals began to move across to Europe around 400,000 years ago.
- Early humans followed suit far later, arriving just 60,000 years ago.
- Neanderthals mysteriously died out shortly afterwards, possibly due to a disease pandemic or hunting by humans.
- It's also thought our ancestors outcompeted their newfound rivals for food and shelter, eventually wiping them from the planet.
The authors used other clues in the genome to estimate when ancient human populations separated.
Super-Archaics are believed to have separated into their own species two million years ago.
This agrees with human fossil evidence in Eurasia dating back 1.85million years.
And the evidence suggests there were three major waves of human migration into Eurasia.
The first was two million years ago when Super-Archaics mvoed north and expanded into a large population.
Then came the Neanderthal-Denisovan ancestors around 700,000 years ago, who quickly interbred with descendants of the Super-Archaics.
And finally, modern humans migrated to Eurasia around 50,000 years ago.
We know these modern humans interbred with other ancient humans, including with 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."
This research was published in the journal Science Advances.
A timeline of life on Earth
The history of the planet in years…
- 4.6billion years ago – the origin of Earth
- 3.8billion years ago – first life appears on Earth
- 2.1billion years ago – lifeforms made up of multiple cells evolve
- 1.5billion years ago – eukaryotes, which are cells that contain a nucleus inside of their membranes, emerge
- 550million years ago – first arthropods evolve
- 530million years ago – first fish appear
- 470million years ago – first land plants appear
- 380million years ago – forests emerge on Earth
- 370million years ago – first amphibians emerge from the water onto land
- 320million years ago – earliest reptiles evolve
- 230million years ago – dinosaurs evolve
- 200million years ago – mammals appear
- 150million years ago – earliest birds evolve
- 130million years ago – first flowering plants
- 100million years ago – earliest bees
- 55million years ago – hares and rabbits appear
- 30million years ago – first cats evolve
- 20million years ago – great apes evolve
- 7million years ago –first human ancestors appear
- 2million years ago – Homo erectus appears
- 300,000 years ago – Homo sapiens evolves
- 50,000 years ago – Eurasia and Oceania colonised
- 40,000 years ago – Neandethal extinction
In other news, an ancient stone carving of a "big butt warrior in tight leggings" has been found in Scotland.
The posh grave of an Iron Age "warrior" buried 2,000 years ago in Roman Britain has been uncovered.
Ancient Chinese people gave their babies coneheads by ‘moulding their skulls’ to show off how rich they were.
And, from headless vikings to ‘screaming’ mummies, here are some of the most gruesome ancient corpses ever found.
What do you make of this discovery? Let us know in the comments!
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