Human DNA

Whether you hail from Surbiton, Ulan Bator or Nairobi, your genetic make-up is strikingly similar to that of every other person on Earth, an analysis concludes today.

Although scientists have long recognised that, despite physical differences, all human populations are genetically similar, the new work concludes that populations from different parts of the world share even more genetic similarities than previously assumed.

All humans are 99.9 per cent identical and, of that tiny 0.1 per cent difference, 94 per cent of the variation is among individuals from the same populations and only six per cent between individuals from different populations.

Nonetheless, the team found that tiny differences in DNA can provide enough information to identify the geographic ancestry of individual men and women.

The results of the study, published today in the journal Science, have implications for understanding ancient human migrations and for resolving an ongoing debate about the use of family histories in medical research, said Prof Marcus Feldman of Stanford University who led the team.

The team analysed DNA from 1,056 people from 52 populations in five major geographic regions of the world: Africa, Eurasia (Europe, the Middle East, Central and South Asia), East Asia, Oceania and the Americas.

To identify specific populations, the research team looked for 377 “microsatellites” – short segments of human DNA that occur in specific patterns, which are passed down from generation to generation.

“Each microsatellite had between four and 32 distinct types,” Prof Feldman said. “Most were found in people from several continents, suggesting that only a tiny fraction of genetic traits are distinctive to specific populations. This means that visible differences between human groups – such as skin colour and skull shape – result from differences in a very small proportion of genetic traits.”

Using powerful statistical techniques that use many independent genes it was possible to pinpoint the ancestral continent of virtually every individual from Africa, East Asia, Oceania and the Americas.

People from Eurasia – which includes Europe, the Middle East and Central/South Asia – were among the most difficult to assign ancestries, Prof Feldman noted, due to a “complex history of migrations, conquests and trade over the past few thousand years.”

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