Archaeologists think that human beings crossed from Eurasia ("the old world") into North America ("the new world") via the Bering Strait, where a "land bridge" once existed, about 15,000 years ago.

Genes and languages are now as informative as archaeology in tracing historical migrations. Languages evolve like living species. Common ancestors separate, adapt to new environments and change. The more recent the split, the closer the relationship. Human beings are closer to chimpanzees than to starfish; and so Spanish and Portuguese sit nearer to each other than to Mandarin.

Geneticists now borrow statistical tests derived by linguists. The world's 7,000 languages cluster into families of common descent. English is in the Indo-European family, part of the Nostratic superfamily. It was a conundrum that Native American languages, the Amerind family, could not readily be linked to the Nostratic group.

Recently, however, statistical tests on the phonetic roots of the minority Yeniseian languages from Siberia linked them to the Amerindian Na-Dene language group. Five thousand miles separate the regions. The new findings support the theory that a small group of hunter-gatherers crossed the Bering Strait before the ice melted, and then founded the population discovered 14,000 years later in the second Eurasian colonisation of the Americas.