A disadvantage to using microsatellites and genetic elements to track the evolution of a species is that they are distributed across the 23 pairs of chromosomes composing the nuclear genome. Scientists are able to focus on microsatellites associated specifically with the Y-chromosome, elliminating the need for extensive sequencing of the entire genome. Until the early 1990's it was not realized that the Y-chromosome exhibited polymorhpism. Polymorphisms can be used as molecular clocks (like the mtDNA) and as such can be conceptualized as a paternal version of mtDNA. Current coalescence times are approximately 100,000-150,000YA.

The novelty of this research lends itself to rapid advances and frequent revisions.

Figure 18: X-chromosome (left) and Y-chromosome (right). Magnification=10,000x