New Delhi:
A study of ancient DNA of mummies and skeletons has come up with striking facts. The study suggests that European colonisation in the late 1400s had a devastating impact and led to the demographic collapse of Native Americans. These skeletons are between 500 and 8,600 years old.
The study also shows a striking absence of the pre-Columbian genetic lineages in modern Indigenous Americans; showing extinction of these lineages with the arrival of the Spaniards.
“Surprisingly, none of the genetic lineages we found in almost 100 ancient humans were present, or showed evidence of descendants, in today’s Indigenous populations,” said joint lead author Bastien Llamas, from University of Adelaide’s Australian Centre for Ancient DNA (ACAD).
“This separation appears to have been established as early as 9,000 years ago and was completely unexpected, so we examined many demographic scenarios to try and explain the pattern,” said Llamas.
Shortly after the initial colonisation, populations were established that stayed geographically isolated from one another, and that a major portion of these populations later became extinct following European contact, he said.
“This closely matches the historical reports of a major demographic collapse immediately after the Spaniards arrived in the late 1400s,” Llamas said.
Researchers from University of Adelaide, University of California at Santa Cruz (UCSC) and Harvard Medical School, studied maternal genetic lineages by sequencing whole mitochondrial genomes extracted from bone and teeth samples from 92 pre-Columbian - mainly South American - human mummies and skeletons.
The ancient genetic signals also provide a more precise timing of the first people entering the Americas - via the Beringian land bridge that connected Asia and the north-western tip of North America during the last Ice Age.
“Our genetic reconstruction confirms that the first Americans entered around 16,000 years ago via the Pacific coast, skirting around the massive ice sheets that blocked an inland corridor route which only opened much later,” said Alan Cooper, Director of ACAD.
“They spread southward remarkably swiftly, reaching southern Chile by 14,600 years ago,” said Cooper. “Genetic diversity in these early people from Asia was limited by the small founding populations which were isolated on the Beringian land bridge for around 2,400 to 9,000 years,” said Lars Fehren-Schmitz, from UCSC.
“It was at the peak of the last Ice Age, when cold deserts and ice sheets blocked human movement, and limited resources would have constrained population size,” Fehren-Schmitz said.
“This long isolation of a small group of people brewed the unique genetic diversity observed in the early Americans,” he said. The study was published in the journal Science Advances.
