Mystery genes – do we have an unknown ancestor?

By Shannon Verhagen 29 July 2016
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Humans could potentially have another ancestor we didn’t know about.

NEW RESEARCH HAS discovered populations from South and Southeast Asia contain a small amount of ancestral DNA – not present in East Asians or Europeans – suggesting some modern humans have another, mystery ancestor.

The research – undertaken by Professor Jaume Bertranpetit from Pompeu Fabra University in Spain along with a team of researchers and published in Nature Genetics this week – involved  whole-genome sequence analysis.

The genome sequences of 60 individuals of different ethnicities from India’s mainland were compared with those of 10 Andamanese individuals as well as publicly available data for other populations.

Unknown, extinct ancestor

The study found a small proportion of the genome sequence in populations from South and South East Asia contained DNA from an unknown, extinct, hominid ancestor.

Dr Alan Cooper, from the University of Adelaide and Australian Centre for Ancient DNA, said at least five ancestral hominids had been present in Southeast Asia – including Neanderthals, Denisovians, Homo floresiensis (‘hobbits’), H. erectus and H. antecessor.

“We already knew there was another species or group of hominids in Southeast Asia who had contributed to the Denisovan genome,” commented Alan, who wasn’t involved in this study.

“This paper further confirms that one other group, maybe the same one, has contributed to modern humans.”

This is not the first time ancestral DNA has been found in modern humans – when Homo sapiens (that’s us) arrived in Southeast Asia about 60,000 years ago, they shared the space with the now extinct Denisovians – and today, Melanesians carry 4% of this ancestral DNA.

There is speculation over the mystery ancestor, with Alan suggesting Homo erectus (“upright man”) or an Asian Homo antecessor (“human pioneer”) as potential hominid groups of interest.

“A crowded stage”

However, without a well preserved specimen – the preservation process is hindered by Asia’s hot and humid climate – Alan said it will be difficult to determine the exact source of the genomic sequence.

“At the moment there’s not any good skeletal remains that are likely to provide DNA,” Alan said.

For now, the genetic information that is available can help scientists piece together what the ancestor potentially looked like.

“At the moment we are able to see the genetic shadow left behind in other genomes, but we’re not sure what fossils it is connected to,” Alan said.

However, it could also be from a previously unidentified ancestral hominid. “I wouldn’t be surprised,” he added.

“What we can say safely is that Asia was a far more crowded stage.”