Aside from carrying genetic information, it seems that human DNA can also function as a historical archive containing information about the intermingling of various human groups throughout history.
A team of researchers has published a new study detailing the intermingling of human groups spanning the last 4,000 years. Using information contained in DNA, the scientists were able to reconstruct a roadmap pinpointing specific periods where different groups interbred. The team published their findings in the online journal Science.
"Modern genetic data combined with appropriate statistical methods have the potential to contribute substantially to our understanding of human history," said lead author Garrett Hellenthal and his colleagues. Hellenthal is a research fellow from the UCL (University College London) Genetics Institute. "We have developed an approach that exploits the genomic structure of admixed populations to date and characterize historical mixture events at fine scales."
Along with the study, the scientists also created a companion site to complement their findings. The companion site contains an interactive map where people can view the effects of intermingling in human populations across history. Aside from providing valuable genetic information, the study can also be potentially useful for fleshing out 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," said Hellenthal and Simon Myers. Myers is a university lecturer in bioinformatics from the University of Oxford.
When two groups of populations previously separated in terms of geography meet and interbreed, they introduce new genetic into the resulting population. This process is referred to as genetic admixture.
"Admixture, the result of previously distant populations meeting and breeding, leaves a genetic signal within the descendants' genomes," said Hellenthal and his colleagues. "However, over time the signal decays and can be hard to trace."
Throughout history, there have been many events that brought about admixture. The genetic segments contained in the DNA of modern humans are the cumulative result of incidents of admixture during certain periods in history. The genetic information about admixture found in human DNA can be correlated to certain time periods depending on race and location. Important historical events such as the Mongol wars of conquest and the opening of the Silk Road coincide with major admixture occurrences.
Despite the fact that DNA segments inherited during admixture events shorten over time, these DNA segments can still give scientists a fair idea regarding how long ago the admixture event happened. However, there are a few key limitations to the process used by the researchers. When two genetically similar groups interbreed, scientists can only give rough estimates regarding the timeline of these events. The process is further complicated when studying the DNA segments resulting from multiple admixture events between two groups. Lastly, the process is also currently limited to studying two separate groups. When a third group is added into the mix, the accuracy of the process drops significantly.
