Genetic ancestry test claims to find 'village where your DNA was formed'

Geneticists claim to have developed a way of finding where
in the world a person's DNA originated.

The ancestry test - called Geographic Population Structure,
or GPS - tries to infer a single home up to 1,000 years ago by comparing a
person's DNA to a set of reference genomes.

In a study published in Nature Communications, GPS calculated the correct country of origin for
83 percent of 600 genomes tested. GPS also pinpointed the home
village for one quarter of a sample of 249 Sardinians and assigned 90 percent
of 243 Oceanians to their correct home island.

The tool's accuracy depends on the range of reference
genomes in its database, as well as a population's history of migration. GPS
predicted that the Brazilian Surui, an indigenous group of coffee farmers,
lived 4,800km from their actual location - equivalent to the distance between London
and Abuja, the capital of Nigeria.

'We were surprised by the simplicity and precision of this
method', said Dr Tatiana Tatarinova, associate professor of research paediatrics
at the University of Southern California, USA, who co-created GPS.

The 596 reference genomes used in the study were genetically diverse, coming from 94 populations across the world. According to the
researchers, many of these populations have stayed in their current location
for 'at least a few centuries'.

Dr Eran Elhaik, co-creator of GPS, explained: 'If we
think of our world as being made up of different colours of soup - representing
different populations - it is easy to visualise how genetic admixture occurs.
If a population from the blue soup region mixes with a population from the red
soup region their offspring would appear as a purple soup'.

'The more genetic admixture that takes place, the more
different colours of soup are introduced which makes it increasingly difficult
to locate your DNA's ancestry', said Dr Elhaik, a geneticist at the University
of Sheffield. GPS models this genetic admixture and calculates a map reference
based on the known locations of genomes in their database.

Critics have argued that GPS does not account for the fact
that people may not inherit DNA from every ancestor (see BioNews 696) nor for the
fact that, in Europe at least, people's ancestors from 1,000 years ago are highly unlikely to have come from
the same place. The study also did not compensate for recombination, the random
shuffling of chromosomes when sex cells are formed.

Mark Thomas, professor of evolutionary genetics at
University College London, told BioNews that the study has been 'over-hyped and
in places the claims made are absurd'.

He cautioned that 'very few people have a single "ancestral
home village" since we have an increasing number of ancestors as we look
further back in time', and described GPS as 'interesting but crude'.