In light of my last post I had to take note when Dienekes today pointed to this new paper in the American Journal of Physical Anthropology, Population history of the Red Sea—genetic exchanges between the Arabian Peninsula and East Africa signaled in the mitochondrial DNA HV1 haplogroup. The authors looked at the relationship of mitochondrial genomes, with a particular emphasis upon Yemen and the Horn of Africa. This sort of genetic data is useful because these mtDNA lineages are passed from mother to daughter to daughter to daughter, and so forth, and are not subject to the confounding effects of recombination. They present the opportunity to generate nice clear trees based on distinct mutational “steps” which define ancestral to descendant relationships. Additionally, using neutral assumptions mtDNA allows one to utilize molecular clock methods to infer the time until the last common ancestor of any two given lineages relatively easily. This is useful when you want to know when a mtDNA haplgroup underwent an expansion at some point in the past (and therefore presumably can serve as a maker for the people who carried those lineages and their past ...