He argues that the Indo-European proto-language diversified after the invention of the wheel, about 5, 000 years ago.

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These are Indo-European, Bantu, Austronesian (from South-East Asia and the Pacific) and Uto-Aztecan (the native vernaculars of the Americas).

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For their studies, the team studied the characteristics of word order in four language families: Indo-European, Uto-Aztec, Bantu and Austronesian.

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This is an Indo-European concoction, derived from avancer, French for "to advance, " and the word sthapna, which means "well grounded" in Sanskrit, the ancient Indian language.

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To do so he looked at three well-studied parts of the linguistic family tree: the Bantu languages of Africa, the Indo-European group from Eurasia and the Austronesians of the Pacific.

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Around a third of the vocabulary differences between modern Bantu speakers arose this way, around a fifth of the differences between speakers of Indo-European languages, and around a tenth of the Austronesians.

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They suspect that it was responsible for the sudden spread of the Indo-European group of humanity about 4, 000 years ago, and also for the more recent spread of the Tutsis in Africa, whose ancestors independently evolved a tolerant version of the gene.

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