 At this time human populations consisted entirely of non-sedentary hunter-gatherer populations, with anatomically modern humans existing alongside archaic human varieties, some of which are still ancestral to the modern human population due to interbreeding with modern humans during the Upper Paleolithic.Estimates of the size of these populations are a topic of paleoanthropology.A late human population bottleneck is postulated by some scholars at approximately 70,000 years ago, during the Toba catastrophe, when "Homo sapiens" population may have dropped to as low as between 1,000 and 10,000 individuals.