The evolution of the mitochondrial D-loop region and the origin of modern man.

The origin of modern man is a highly debated issue that has recently been tackled by using mitochondrial DNA sequences. The limited genetic variability of human mtDNA has been explained in terms of a recent common genetic ancestry, thus implying that all modern-population mtDNAs originated from a single woman who lived in Africa less than 0.2 Mya. This divergence time is based on both the estimation of the rate of mtDNA change and its calibration date. Because different estimates of the rate of mtDNA evolution can completely change the scenario of the origin of modern man, we have reanalyzed the available mitochondrial sequence data by using an improved version of the statistical model, the "Markov clock," devised in our laboratory. Our analysis supports the African origin of modern man, but we found that the ancestral female from which all extant human mtDNAs originated lived in a time span of 0.3-0.8 Mya. Pushing back the date of the deepest root of the human implies that the earliest divergence would have been in the Homo erectus population.