Previous studies of human genomic variation tended to look at changes called single nucleotide polymorphism, variations that involve just one nucleotide, commonly referred to as SNP. However, the study published today suggests that structural variation is responsible for a larger number of physical and cognitive differences between the genomes of two individuals than SNPs. The role that SV plays in human variability has not been well understood because of cost-prohibitive and imprecise technology used in previous research.