NEW APPROACHES TO DATING SUGGEST A RECENT AGE FOR THE HUMAN MTDNA ANCESTOR

The most critical and controversial feature of the African origin hypothesis of human mitochondrial DNA (mtDNA) evolution is the relatively recent age of about 200 ka inferred for the human mtDNA ancestor. If this age is wrong, and the actual age instead approaches 1 million years ago, then the controversy abates. Reliable estimates of the age of the human mtDNA ancestor and the associated standard error are therefore crucial. However, more recent estimates of the age of the human ancestor rely on comparisons between human and chimpanzee mtDNAs that may not be reliable and for which standard errors are difficult to calculate. We present here two approaches for deriving an intraspecific calibration of the rate of human mtDNA sequence evolution that allow standard errors to be readily calculated. The estimates resulting from these two approaches for the age of the human mtDNA ancestor (and approximate 95% confidence intervals) are 133 (63-356) and 137 (63-416) ka ago. These results provide the strongest evidence vet for a relatively recent origin of the human mtDNA ancestor.