Two researcher teams performed the most thorough genetic analysis yet on samples from the Human Genome Diversity Project (HGDP), confirming that populations lost genetic variation as they migrated farther from Africa and discovering that copy number variants (rearrangements within longer stretches of DNA) differ between human populations similarly to SNPs.

Previous studies had either looked at fewer “markers”–sites of genetic variation–or fewer population groups. The HGDP covers more than 50 geographic groups from all over the globe.