I found this news story on BBC News this morning rzlating to a new paper in Nature (Pagani et al. 2016).
BBC News: DNA hints at earlier human exodus from Africa
"Present-day people outside Africa were thought to descend from a group that left their homeland 60,000 years ago.
Now, analysis of nearly 500 human genomes appears to have turned up the weak signal of an earlier migration.
But the results suggest this early wave of Homo sapiens all but vanished, so it does not drastically alter prevailing theories of our origins.
Writing in the academic journal Nature, Luca Pagani, Mait Metspalu and colleagues describe hints of this pioneer group in their analysis of DNA in people from the Oceanian nation of Papua New Guinea."
..
"Yet we had known for some time that groups of modern humans made forays outside their "homeland" before 60,000 years ago.
"The first instance when we thought we were seeing something was when we used a technique called MSMC, which allows you to look at split times of populations," said co-author Dr Mait Metspalu, director of the Estonian Biocentre in Tartu, told BBC News.
His colleague and first author Dr Luca Pagani, also from the Estonian Biocentre, added: "All the other Eurasians we had were very homogenous in their split times from Africans.
"This suggests most Eurasians diverged from Africans in a single event... about 75,000 years ago, while the Papuan split was more ancient - about 90,000 years ago. So we thought there must be something going on."
It was already known that Papuans, along with other populations from Oceania and Asia, derive a few per cent of their ancestry from Denisovans, an enigmatic sister group to the Neanderthals.
The researchers tried to remove this component, but were left with a third chunk of the genome which was different from the Denisovan segment and the overwhelming majority which represents the main out of Africa migration 60,000 years ago."
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The paper mentions that no mtDNA or Y-DNA dating from that Early Out-of-Africa (OoA) migration was identified among Papuans.
BBC News: DNA hints at earlier human exodus from Africa
"Present-day people outside Africa were thought to descend from a group that left their homeland 60,000 years ago.
Now, analysis of nearly 500 human genomes appears to have turned up the weak signal of an earlier migration.
But the results suggest this early wave of Homo sapiens all but vanished, so it does not drastically alter prevailing theories of our origins.
Writing in the academic journal Nature, Luca Pagani, Mait Metspalu and colleagues describe hints of this pioneer group in their analysis of DNA in people from the Oceanian nation of Papua New Guinea."
..
"Yet we had known for some time that groups of modern humans made forays outside their "homeland" before 60,000 years ago.
- Fossilised remains found at the Qafzeh and Es Skhul caves in Israel had been dated to between 120,000 and 90,000 years ago.
- Then in 2015, scientists working in Daoxian, south China, reported the discovery of modern human teeth dating to at least 80,000 years ago.
- An additional piece of evidence recently came from traces of Homo sapiens DNA in a female Neanderthal from Siberia's Altai mountains. The analysis suggested that modern humans and Neanderthals had begun mixing around 100,000 years ago - presumably outside Africa."
"The first instance when we thought we were seeing something was when we used a technique called MSMC, which allows you to look at split times of populations," said co-author Dr Mait Metspalu, director of the Estonian Biocentre in Tartu, told BBC News.
His colleague and first author Dr Luca Pagani, also from the Estonian Biocentre, added: "All the other Eurasians we had were very homogenous in their split times from Africans.
"This suggests most Eurasians diverged from Africans in a single event... about 75,000 years ago, while the Papuan split was more ancient - about 90,000 years ago. So we thought there must be something going on."
It was already known that Papuans, along with other populations from Oceania and Asia, derive a few per cent of their ancestry from Denisovans, an enigmatic sister group to the Neanderthals.
The researchers tried to remove this component, but were left with a third chunk of the genome which was different from the Denisovan segment and the overwhelming majority which represents the main out of Africa migration 60,000 years ago."
--------------
The paper mentions that no mtDNA or Y-DNA dating from that Early Out-of-Africa (OoA) migration was identified among Papuans.
Pagani et al. said:Y chromosome and mtDNA haplopgroup analysis. The presence of an extinct xOoA trace in the genome of modern Papuans may seem at odds with analyses of mtDNA and Y chromosome phylogenies, which point to a single, recent origin for all non-African lineages (mtDNA L3, which gives rise to all mtDNA lineages outside Africa has been dated at ~ 70,000 years old). However, uniparental markers inform on a small fraction of our genetic history, and a single origin for all non-African lineages does not exclude multiple waves OoA from a shared common ancestor. We show analytically (Supplementary Information 2.2.12) that, if the xOoA signature entered the genome of Papuan individuals > 40 kya, their mtDNA and Y lineages could have been lost by genetic drift even assuming an initial xOoA mixing component of up to 35%.