6000 year old skeletons with no connection to modern humans found in Colombia

News.com.au

4 days ago

We don't know where they came from. We don't know where they went. The unique DNA of an ancient tribe of hunter-gatherers is adding to the confusion surrounding the source of South America' s first inhabitants.
The story of the region's human settlement is already confusing enough.
Some argued it was colonised by Stone Age clans crossing the Atlantic Ocean from Africa and the Pacific Ocean from as far away as Australia.
But the prevailing argument is that a migration of Clovis peoples out of Siberia followed an Alaskan ice bridge into North America some 20,000 years ago.
Scientists have been squabbling over who went where, when, for decades.
The modern discipline of genetics can offer answers. And add to the confusion. A new analysis of mitochondrial DNA (inherited from mothers) alongside complete genome data of 21 ancient burials presents a connect-the-dots puzzle of migration spanning millennia.
One group, however, stands out.
A tribe of hunter-gatherers who settled the Bogotá Altiplano mountains in what is now Colombia were different. But their isolated plateau sits near the exit from the narrow land bridge that linked Central and South America.
Anthropologists don't know where they fit.
They're not directly related to the ancient North American Clovis peoples.
And their genetic heritage is yet to be found in subsequent Native South American populations.
They appeared some 6000 years ago.They vanished about 2000 years ago.
And there's no hint as to why.
First arrivals
The oldest human remains found in South America are those of 'Luzia', otherwise dubbed 'The First Brazilian'. This 12,000-year-old woman was most likely from among the first wave of settlers to reach the southern continent. DNA shows they were descendants of the Clovis migration – not African or Australian seafarers as previously believed.
A second wave of North American tribes arrived around 9000 years ago, and a third some 5000 years later.
'However, a region that has not been investigated through ancient genomics so far is Colombia, the entry point into South America,' the authors of the study, published in the May edition of the journal Science Advances, state.
And that's what they sought to address.
They examined five archaeological sites across the Bogota Altiplano plateau. Genetic material was extracted from teeth and bones of 21 skeletons dating from 6000 to 500 years old.
The researchers argue the oldest remains must have been from a lingering branch of the first migration of humans into South America. But even then, their clan must have been unique.
'We show that the hunter-gatherer population from the Altiplano dated to around 6000 yr B.P. lack the genetic ancestry related to the Clovis-associated Anzick-1 genome and to ancient California Channel Island individuals,' the study finds.
'The analysed Preceramic individuals from Colombia do not share distinct affinity with any ancient or modern-day population from Central and South America studied to date.'
Whatever the case, their isolated mountain plateau could have contributed to its longevity. Until it didn't.
'We couldn't find descendants of these early hunter-gatherers of the Colombian high plains — the genes were not passed on,' explains Kim-Louise Krettek of the University of Tubingen.
'That means in the area around Bogotá there was a complete exchange of the population.'
Inevitability of change
Who were these people? What did they look like? How did they settle in their strange new homeland?
By the time the descendants of the Clovis tribes that crossed the Bering Strait out of northern China and Siberia reached South America, 7000 years of genetic mutation and evolution were already well down the path towards creating distinct new communities.
The Bogota Altiplano was among them.
Then, their mountaintop plateau home likely kept them isolated from external influence. Until strange new people began climbing the slopes 4000 years ago.
The march of progress is relentless.
The high tableland transitioned from its hunter-gatherer society into an agrarian economy in a process completed within 2000 years.
DNA shows the new people came from Central America. Archaeology reveals they brought with them innovations including pottery and planting seeds.
'In addition to technological developments such as ceramics, the people of this second migration probably also brought the Chibchan languages into what is present-day Colombia. Branches of this language family are still spoken in Central America today,' says co-author Andrea Casas-Vargas of the Universidad Nacional de Colombia.
Whether exterminated through war or overwhelmed in numbers, the earlier Bogota Altiplano people vanished.
'The cultural transition between the Preceramic and Herrera periods is associated with a seemingly complete replacement of the local genetic profile,' the study reads.
'That genetic traces of the original population disappear completely is unusual,' adds National University of Colombia study participant Andrea Casas-Vargas.