An article in the most recent issue of Science produced what they called an ‘atlas' of worldwide human admixture history. They used genetic data and identified over 100 admixture events that occurred over the past 4000 years. The authors identified admixture events by looking at alleles at multiple successive SNPs in order to identify the shared portions of DNA between individuals in different populations to determine ancestry. They found the genetic impact of several historical events including the Mongol empire, Arab slave trade, Bantu expansion, first millennium CE migrations in Eastern Europe, and European colonialism. The authors also identified admixture events that did not correspond with any recorded historical events.