Out of Africa and into an archaic human melting pot

Out of Africa and into an archaic human melting pot
Proposed route of the ancestors of modern humans out of Africa and through Island Southeast Asia. Credit: University of Adelaide

Genetic analysis has revealed that the ancestors of modern humans interbred with at least five different archaic human groups as they moved out of Africa and across Eurasia.

While two of the archaic groups are currently known—the Neandertals and their sister group the Denisovans from Asia—the others remain unnamed and have only been detected as traces of DNA surviving in different modern populations. Island Southeast Asia appears to have been a particular hotbed of diversity.

Published in the Proceedings of the National Academy of Sciences (PNAS), researchers from the University of Adelaide's Australian Centre for Ancient DNA (ACAD) have mapped the location of past "mixing events" (analysed from existing ) by contrasting the levels of archaic ancestry in the genomes of present-day populations around the world.

"Each of us carry within ourselves the genetic traces of these past mixing events," says first author Dr. João Teixeira, Australian Research Council Research Associate, ACAD, at the University of Adelaide. "These archaic groups were widespread and genetically diverse, and they survive in each of us. Their story is an integral part of how we came to be.

"For example, all present-day populations show about 2% of Neandertal ancestry which means that Neandertal mixing with the ancestors of modern humans occurred soon after they left Africa, probably around 50,000 to 55,000 years ago somewhere in the Middle East."

Out of Africa and into an archaic human melting pot
Proposed route of the ancestors of modern humans out of Africa and through Island Southeast Asia. Credit: University of Adelaide

But as the ancestors of modern humans travelled further east they met and mixed with at least four other groups of archaic humans.

"Island Southeast Asia was already a crowded place when what we call modern humans first reached the region just before 50,000 years ago," says Dr. Teixeira. "At least three other archaic human groups appear to have occupied the area, and the ancestors of modern humans mixed with them before the archaic humans became extinct."

Using additional information from reconstructed migration routes and fossil vegetation records, the researchers have proposed there was a mixing event in the vicinity of southern Asia between the modern humans and a group they have named "Extinct Hominin 1."

Other interbreeding occurred with groups in East Asia, in the Philippines, the Sunda shelf (the that used to connect Java, Borneo and Sumatra to mainland East Asia), and possibly near Flores in Indonesia, with another group they have named "Extinct Hominin 2."

"We knew the story out of Africa wasn't a simple one, but it seems to be far more complex than we have contemplated," says Dr. Teixeira. "The Island Southeast Asia region was clearly occupied by several archaic human groups, probably living in relative isolation from each other for hundreds of thousands of years before the ancestors of modern humans arrived.

"The timing also makes it look like the arrival of was followed quickly by the demise of the archaic groups in each area."


Explore further

Ancient molar points to interbreeding between archaic humans and Homo sapiens in Asia

More information: João C. Teixeira et al. Using hominin introgression to trace modern human dispersals, Proceedings of the National Academy of Sciences (2019). DOI: 10.1073/pnas.1904824116
Citation: Out of Africa and into an archaic human melting pot (2019, July 15) retrieved 22 August 2019 from https://phys.org/news/2019-07-africa-archaic-human-pot.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
789 shares

Feedback to editors

User comments

Jul 15, 2019
The Island Southeast Asia region was clearly occupied by several archaic human groups, probably living in relative isolation from each other for hundreds of thousands of years before the ancestors of modern humans arrived.
The timing also makes it look like the arrival of modern humans was followed quickly by the demise of the archaic human groups in each area.


Sounds about right.

Jul 15, 2019
Why a modern map of Africa and Europe? The coastline was markedly different then with lower sea levels. Georaphy is probably more omportant than climate change to help explain the migration from Africa.

Jul 16, 2019
IMO, not all hominids came 'out of Africa', but different groups sprang up in different parts of the world. Even isolation can't account for the fact that White Caucasoids have Neanderthal DNA, but sub-Saharan Black Africans have no Neanderthal DNA at all.
There doesn't seem to be any data on when Neandertals had left Africa. The same with Denisovans. If these two groups had come out of Africa at all, where is the evidence for it?

Jul 16, 2019
The out of Africa Myth

SEU:- Even isolation can't account for the fact that White Caucasoids have Neanderthal DNA, but sub-Saharan Black Africans have no Neanderthal DNA at all

There have always been these discrepancies

Jul 17, 2019
In the age of DNA testing, it has become more apparent that life sprang up in many places in the world, where the weather and other conditions were ripe for organisms to have evolved. Conditions in which such organisms could thrive and reproduce with little, if any, harmful incidents to prevent or hamper their generation. That hominin artifacts have been found in southeast Asia, eastern Europe and other locations that had good conditions for growth and safety are indications of the positiveness of the natural order.

Jul 22, 2019
The paper is an interesting review and synthesis, but I would like to see an actual model such as the ones that provided the data.

And the author's like to pull up signals that papers did not assign as noteworthy as long as those signals were close to the Neanderthal/Denisovan split. Granted, crossbreeding with older archaics would be extraordinary, but their references frequently found such signals too.

The timing also makes it look like the arrival of modern humans was followed quickly by the demise of the archaic human groups in each area.


Yes, they noted that it would be an expected result whether or not crossbreeding happened, since recent analyses that could compare whole sequence Neanderthals uncovered that breeding barriers between them and us were rising. That accounts for about a factor 10 lowering of Neanderthal alleles in the extant population.

Jul 22, 2019
Why a modern map of Africa and Europe? The coastline was markedly different then with lower sea levels. Georaphy is probably more omportant than climate change to help explain the migration from Africa.


They did use a sea level reconstruction where it was expected to make a real difference in the migration data, for the archaics in Southeast Asia, see figure 2. But yes, the paper (maybe not the supplement) made choices without commenting on them.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more