DNA test reveals how your ancestors lived

Scottish scientists have developed a genetic test that can reveal the kind of communities our ancestors lived in by showing if they came from a society where marriages between relatives were commonplace.

The research, conducted by the University of Edinburgh, shows that an individual's DNA records a "historical archive" of where they come from.

The study, published in the journal PLoS One, found that it was possible to determine whether someone's ancestors came from small, isolated communities, or from large and cosmopolitan populations.

The team found it was possible to detect whether a person's parents or ancestors were related in any way - for example whether they came from a community where marriage between cousins was commonplace.

The findings could help to identify those communities where low genetic diversity could increase the risk of genetic illnesses, such as cystic fibrosis.

The scientists analysed the DNA of more than 1,000 people across 51 ethnic groups, including Amazonian tribes in South America, Europeans and Pacific Islanders.

They identified those that had inherited the same genetic material from their mother and father. This trait - where a person inherits the same genetic material from both parents, called homozygosity - is an indication that their parents have a common ancestor.

The researchers found native South Americans had the highest proportion of this shared DNA, suggesting that those communities were small and isolated over many generations.

By contrast, African communities had the lowest degree of genetic similarity, indicating a more diverse population over time. The team believes this could be explained by the fact that humans originated in Africa and so have had the most time to develop a diverse gene pool.

Dr Jim Wilson, Royal Society Research Fellow at the University of Edinburgh, said: "The exciting thing about these results is that it shows our genes are recording the history of movements in our population.

"It's like an archive being written in genetic code, so that we can understand the way our populations have developed from the distant past.

"The findings are also important because it highlights those areas of the world where genetic similarity is common - and this can be a risk factor for some diseases like cystic fibrosis, which can be caused when you inherit a faulty gene from both parents."

Dr Wilson said the test would be interesting to people researching their ancestors and trying to find out more about their background.

"They can find out whether they came from rather large, diverse, cosmopolitan populations or whether they came from smaller, more isolated populations, or if indeed there had been cousin marriage," he said.

The test is for sale for those interested in tracking their genetic history.Dr Wilson said he would be taking the research forward to look at whether homozygosity is a risk factor for high blood pressure and high cholesterol.

"There are some suggestions that it is, but we are still trying to work this out," he said.