( CNN ) -- Most people are carrying around historical records in their DNA , with clues to how people from genetically distinct groups intermingled over the last 4,000 years . That 's the conclusion of a new study in the journal Science . Researchers set out to pinpoint which groups intermixed , and when , over thousands of years , using modern DNA . They thought this information could complement other historical records . `` The results suggest DNA is indeed a powerful means of reconstructing history , which then might be used to identify the genetic legacies of historically well-attested events ... and highlight surprising events with a less clear historical context , '' authors Garrett Hellenthal and Simon Myers wrote in an e-mail . The scientists have created an interactive map showcasing their findings . You can explore the map in detail on the researchers ' website , admixturemap.paintmychromosomes.com . The technical term for people from genetically different groups having babies together is `` genetic admixture . '' This has happened throughout history when people migrated into a new geographic region where others were already living . Researchers say there have been many such admixture events among people from populations that were separated by thousands of miles . Sometimes populations adjacent to each other have distinct ancestry and history . Did you know that your DNA contains genetic segments you 've inherited from groups that intermingled in the past ? Researchers can look at these signatures for clues about major historical mixings of populations . DNA from a person today can also give scientists an idea of how long ago two groups genetically mixed . The more time that has passed since the admixture event , the shorter the inherited DNA segments from the original groups are likely to be . That 's because there would have been more generations in between , and there would have been reshuffling of genetic material in each generation . There are limitations to the method , however . When genetic mixing involves more than three groups , the researchers ca n't identify those specific events . The researchers were also limited in how well they could estimate when the same , or very similar , groups interbred on multiple occasions in one descendant group 's history . Oldest human DNA found in Spain . The researchers looked at a genetic data set of 1,490 people who come from 95 genetically distinct groups worldwide . Their software , Globetrotter , was able to describe genetic mixing events dating back about 4,500 years . The expansion of the Mongol empire , which took place from 1206 to 1368 , appears to have been highly influential on many populations in Europe and Asia . Previous studies have also supported that idea . Genghis Khan and his armies began this monumental historical event that influenced seven populations included in this study . The Arab expansion and slave trade , which began around the seventh century , also had a large genetic impact on many groups , including people from around the Mediterranean , the Arabian Sea and the Persian Gulf . The study 's findings are consistent with that historical timeframe , but suggest that sub-Saharan Africans and Moroccans mixed earlier . A group called the Kalash , from Pakistan , appears to come from an admixture event that happened sometime before 206 B.C. , when people from a more European group hooked up with a more Central/South Asian group . Researchers say the Kalash are geographically isolated , originating in the Hindu Kush mountains , which is why they do n't show genetic signatures of a more recent admixture event . Local tradition says the Kalash are descended from the army of Alexander the Great ; the new study does not rule that out , since the time period of the mixing event could have been about right . `` We have tried to let the genetic information 'speak ' in this study , but future interpretation of signals -- especially in follow-up studies of specific regions -- would benefit from expertise from ... historians , linguists and others , '' Hellenthal and Myers said . Some groups showed genetic signals that the researchers were unable to precisely interpret . For instance , genetic material from French people suggests an intermixing between northern and southern Europeans and northern Africans , between 785 and 1,385 years ago , but the event itself is still unclear . The researchers were not able to pick up signals of some well-established historical intermixings , such as migrations into the United Kingdom from northern European groups , because of the small sample sizes . It is possible that a mutation could arise in two populations independently , but that is thought to be rare . `` If two individuals share a mutation , it is statistically much more likely that the mutation occurred in a common ancestor of both individuals , rather than arising independently in the ancestors of each of them , '' Hellenthal and Myers said . The researchers are involved in a project called People of the British Isles , which is looking specifically at the genetic origins of people from the United Kingdom . Other projects are looking in more depth at areas such as the Caribbean , Ethiopia and the Americas . The researchers say in the study that as whole-genome sequencing improves and analyses are able to incorporate more people as well as ancient DNA , we may reach a `` better understanding of ancient events where little or no historical record exists , to identify many additional events ... and to provide more precise event characterization than is currently possible . '' There may also be implications for public health , as researchers get better at identifying disease risks that are higher in specific populations . Baby 's DNA deconstructed before birth .
Genetic admixure : When people from different groups interbreed . There have been many instances of this happening . Researchers used DNA to track historical mixing .