Colour 'no guide to ancestry'

" Our study makes clear the hazards of equating colour or race with geographical ancestry "

A group of scientists - writing in the journal Proceedings of the National Academy of Sciences - have found that people who appear white may genetically be mainly African, while people who look black may genetically be European or Amerindian.

The scientists, from the University of Minas Gerais in Brazil and the University of Porto in Portugal, said their data indicated that, in Brazil, colour was a weak predictor of African ancestry.

"There is wide agreement among anthropologists and human geneticists that, from a biological standpoint, human races do not exist," said one of the researchers, Sergio Pena.

"Yet races do exist as social constructs," Dr Pena and his colleagues said.

Colour roots

The research took place in Brazil and on the island of Sao Tome, a former Portuguese colony off the African coast.

" Races do exist as social constructs "

Brazil's population comes from three separate ethnic groups: the original Amerindians, Europeans, and Africans.

These groups have inter-married and inter-bred, yet some Brazilians are popularly regarded as white, others as black.

The researchers found 10 gene variations that could reliably tell apart - genetically - 20 men from northern Portugal and 20 men from Sao Tome.

But the genetic differences did not have anything to do with physical characteristics such as skin or hair colour, the researchers found.

Poor guide

They next tested two groups - 173 Brazilians "classified" as white, black, or intermediate based on arm skin colour, hair colour, and nose and lip shape, and 200 men living in major metropolitan areas who classified themselves as white.

The results threw up some surprises: maternal DNA suggested that even the "white" people had about 33% of genes that were of Amerindian ancestry and 28% African - indicating that European men often fathered children with black and Indian women.

"It is interesting to note that the group of individuals classified as blacks had a very high proportion of non-African ancestry (48%)," they wrote.

"Our study makes clear the hazards of equating colour or race with geographical ancestry and using interchangeably terms such as white, Caucasian and European on one hand, and black, Negro or African on the other, as is often done in scientific and medical literature," the scientists' report said.