Short tandem repeats (STRs) are DNA sequences of 1–6 bp that are repeated in tandem from several to hundreds of times. Because they mutate frequently by adding or deleting copies of the repeat, STRs can have many distinct alleles in a population. Given their high mutation rate and polymorphism, STRs have been widely used in population genetic studies. Notably, STR typing has made a great contribution to understanding human evolutionary history. For example, in 2009, Tishkoff et al. genotyped 848 STRs in thousands of African people and used them to reconstruct African substructure and human population histories, providing substantial evidence for the migration of modern humans out of Africa and across the globe.

Despite their utility and importance — many STR loci are associated with genetic disorders, including fragile X syndrome and Huntington disease — studying STRs on a genomic scale has been difficult. Challenges with sequencing and mapping them back to the human reference genome have meant that SNP typing has largely replaced STR typing in human population genetics studies and genome-wide association studies. Fortunately, the recent development of new algorithmic tools and advances in sequencing technologies have enabled the examination of STR polymorphisms and diversity on a genomic scale. In 2023, Shi et al. published a research article in Nature Communications characterizing genome-wide STR variation in 6,487 global human genomes, including new data from 3,983 Chinese individuals and previous data from the 1000 Genomes Projects (1KGP dataset). Their findings expand our understanding of the genetic diversity of STRs in global populations, shedding light on both population-specific and across-population genetic variation.