Where are you from? Naming a childhood town is an easy reply for many, but for an adopted child or young refugees separated from their parents, the answer may never come. Now, a new app could help those who are unaware of their ancestral home. Using only DNA sequences, the program can trace how far away a person lives from the land of their forebears, according to a study published today in Nature Communications. The system relies on admixture—a genetic principle that argues that when a family migrates across a geographic barrier into a new location, they start mating with the locals; new traits start blending into their gene pool, and this genetic diversity provides a ruler for gauging the distance from home. The researchers started with a genome database of people from 54 worldwide regions (dots in map above). The subjects had historic ties to their regions dating back centuries. Using this info, the team built an admixture algorithm, dubbed Geographic Population Structure (GPS), which they tested with the genetic info from 600 DNA samples composed of 98 global subpopulations, such as Romanians or the Punjabis of northern India. Based solely on genetic markers, GPS could place individuals within their country of origin 83% of the time. Half of the subjects were pinpointed within 87 km of their reported point of origin. For instance, all female subjects from the mountain commune of San Basilio, Sardinia, were placed in their original village (inset). But the biggest claim made by the study is that humans are a highly mixed species with no evidence for races.