The DNA of Neanderthals and of an unidentified ancient hominin have been found in the centromere region of chromosome 11 in non-African people. In addition, ancient centromere haplotypes dating back 500,000 years have been found specifically on the X chromosome; one of these centromere haplotypes is only present in modern humans from the African continent. The X chromosome has a role in sex determination, intelligence, memory, X-linked genetic diseases and smell.
The alpha satellite region of the X chromosome centromere is extremely conserved. Phylogenetic analysis has shown that five physical domains exist within this region and that each one contains monomers from different and distinct phylogenetic clades. The extreme conservation at the X chromosome-specific DXZ1 array located at the edge of the alpha satellite region in primates (including chimpanzee, gorilla, orangutan, vervet, macaque, and baboon) demonstrates the extreme ancestral nature of the X chromosome centromere.