Clearly, all of these possibilities will require further analysis and testing in the course of future research. But the implication seems clear that many of the behavioral innovations reflected in the southern African archaeological records between
ca. 80,000 and 60,000 B.P. could have led to a substantial increase in the carrying capacity of the environment for human populations and, accordingly, to a major expansion in human population numbers and densities. Even allowing for the imprecisions in current DNA dating estimates, the apparent coincidence between these major behavioral changes and the estimated timing of the population expansions reflected strongly in both the mtDNA mismatch and lineage-analysis data seems hard to ignore.
It should be emphasized that there is no necessary implication that population numbers in Africa as a whole increased dramatically at this time. Indeed, it could be that total population numbers in Africa decreased significantly at this time, owing to the onset of extremely dry conditions in many parts of Africa between ca. 60,000 and 30,000 B.P. (31, 44). The point is simply that increased levels of technological efficiency and economic productivity in one small region of Africa could have allowed a rapid expansion of these populations to other regions and an associated competitive replacement (or absorption) of the earlier, technologically less “advanced,” populations in these regions