Scientists have developed a genetic test that reveals how diverse a person’s ancestors were.
Research conducted by the University of Edinburgh has shown that an individual’s DNA records a historical archive of where they come from.
The study has found that it is possible to determine whether a person’s ancestors came from small, isolated communities, or from large, cosmopolitan populations.
It is also possible to detect whether a person’s parents or ancestors were related in any way - for example whether they come from a community where marriage between cousins is commonplace.
The team says the findings could help to identify those communities where low genetic diversity could increase the risk of genetic illnesses, such as cystic fibrosis.
The findings are published in the journal PLoS One.
Scientists analysed the DNA of more than 1000 people across 51 ethnic groups, including Amazonian tribes in South America, Europeans and Pacific Islanders.
They identify 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 results showed that 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 believe 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, of the Centre for Population Health Sciences at the University, said: "This study 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 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.