A new pathway for African exodus

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London, Oct 14 : Researchers have discovered what they claim could jolly well be a possible new pathway used by early modern humans for dispersing into other continents from Africa.

Earlier studies had focused on the Nile Valley as the principal route of the early representatives of our species to expand out of Africa to colonise the rest of the world.

Now an international team from universities of Oxford, Bristol, Southampton and Hull in Britain, and Tripoli in Libya has carried out a new study that proposes a “wet corridor” via Libya for human migrations, the ‘BBC News’ portal reported.

According to the researchers, rivers once flowed from the central Saharan watershed all the way to the Mediterranean and this may have enabled modern humans to spread beyond their ancestral homeland about 120,000 years ago.

Previous data showed that there was increased rainfall across the southern part of the Sahara -- which covers most of North Africa -- between 130,000 and 170,000 years ago in a gap between Ice Ages known as the last interglacial period.

In their study, the team investigated whether these wetter conditions had reached a lot further north than earlier thought.

Using geochemical tests, they showed the fossil river channels crossing the Sahara in Libya were active during the last interglacial. “And, this would have created vital water courses across an otherwise arid region,” according to them.

The researchers also analysed the forms, or isotopes, of different chemical elements in snail shells from two sites in the fossil river channels and from the shells of planktonic microfossils in the Mediterranean.

After the tests revealed a distinct volcanic signature to these shells, which was quite different to rocks from the surrounding sites, the team concluded that water flowing from the volcanic mountains of central Sahara was the only possible source of this signature.

“It’s a possible route that the early modern humans could have taken,” said lead author Anne Osborne of University of Bristol, whose study has been published in the latest issue of the PNAS journal.