Phylogenetic Relationships (Biomolecules)

Abstract

Biomolecules, in particular DNA, assist us in generating and testing hypotheses about human evolutionary history. Molecular analyses testing for and then utilizing a local molecular clock can inform us as to the timing of the split between different lineages or populations. When applied to the split between hominins and chimpanzees, for instance, the molecular clock estimates of their divergence date places constraints on interpretations of the growing fossil record from the Late Miocene and Early Pliocene. The pattern and distribution of modern human variation can be used to extrapolate back in time to infer when and where the modern human gene pool arose. Mitochondrial DNA and Y chromosome sequences and markers have been extensively surveyed in populations from around the world. Numerous nuclear loci and other markers, such as microsatellites and Alu insertions, have similarly been sampled and analyzed. The majority of such analyses point toward a relatively recent origin for modern human diversity from a small population in Africa within the last 200 kyr, with a subsequent dispersal into Eurasia less than 100 ka. The question then remains if these modern migrants met and hybridized with the existing archaic populations. Analyses of ancient mitochondrial sequences from 10 Neanderthals strongly suggest that Neanderthal females did not contribute to the modern human mitochondrial gene pool. Coupled with evidence from the fossil and archeological records, a recent African replacement model best fits the existing data.