The phylogenetic relationships within the genus "Nycticebus" have been studied with modern molecular techniques, using DNA sequences derived from the mitochondrial DNA markers D-loop and cytochrome "b" from 22 slow loris individuals. In this analysis, most of the recognized lineages of "Nycticebus", including the pygmy slow loris, were shown to be genetically distinct, and the species was shown to have diverged earlier than the other slow loris species, beginning perhaps 2.7 million years ago. Analysis of nucleotide sequence diversity from individuals taken from the boundary areas between southern China and Vietnam (a region of sympatry between the pygmy slow loris and the Bengal slow loris) show that the pygmy slow loris is not subject to the same introgressive hybridization as the Bengal slow loris ("N. bengalensis"). The authors of the study suggest that the low polymorphism of pygmy slow lorises may be due to a founder effect, and that the individuals they used in the study originate from an ancestor that lived in middle or southern Vietnam between 1860 and 7350 years ago.