The significance of the magnetic stripes was only revealed when their ages were discovered from dating magnetic reversals in volcanic rocks accessible on land.

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For more, see: 'Report that much of Africa has Eurasian ancestry is mistaken'.

A 4,500-year-old skeleton from a cave in Ethiopia has produced Africa’s first ancient human genome.

These polarity reversals are therefore recorded in the rocks forming at the Mid Atlantic Ridge every time the Earth’s magnetism changes from a normal field (as it is today) to a reversed field (as it was about 0.78 million years ago).

When these variations in the magnetic rocks are mapped on the ocean bed they are seen to line up in a series of alternating “magnetic stripes”, rather like barcodes.

The team also found vestiges of these migrants’ DNA in people all across sub-Saharan Africa — probably carried by later migrations, such as the expansion of Bantu-speaking groups from West Africa to other parts of the continent around 1,000 years ago.

Carles La Lueza-Fox, a palaeogeneticist at the Institute of Evolutionary Biology in Barcelona, Spain, says that the first ancient genome from Africa is an important milestone.Yet Africa has missed out on this DNA-based revolution, in part because genetic material degrades quickly in the hot temperatures of the continent.In 2011, archaeologists working with Gamo tribesman in the highlands of southwest Ethiopia discovered Mota Cave, 14 metres wide and 9 metres high, overlooking a nearby river.The man’s DNA suggests that Middle Eastern farmers migrated into Africa several thousand years ago, leaving traces of their Eurasian ancestry in the genomes of many modern-day Africans.Modern humans, Homo sapiens, emerged in Africa around 200,000 years ago, before populating nearly every corner of the planet.You will be re-directed back to this page where you will see comments updating in real-time and have the ability to recommend comments to other users.