Africa, dating back to 60,000 years ago

An interesting story begins to emerge from these relatively isolated data. It doesn't have to be the right story at this stage as I think it's important that people begin to look at the various pieces of the puzzle with the idea of putting them together. We need to radically reorganize how we think about our ancestors and we'll have to try out some ideas and discard them before we come up with the most plausible explanation.

Still, I think it's fairly clear that from about 200,000 BCE through 70,000 BCE human populations went through periods of migration and diversification. They must have been increasing their numbers both in the north (Neanderthals) and in the warmer regions of Africa and Asia (modern humans) and expanding away from their traditional centers of habitation. And then the Toba event happened. This massive supervolcano erupted and probably threw the planet into a downward spiral of cold temperatures. That may explain why sources disagree on the dating of the last glacial and previous interglacial periods.

Most modern humans probably died. Scientists estimate as few as 10,000 people (comprising about 2,000 mating couples and close relatives) survived to carry on the human race. Now, that does not mean that all 10,000 people had to be located in Africa. Nor does it mean that they all had to be modern humans. And it could be that a larger number of people survived. Still, it seems certain that the most significant human population to survive was probably located in south Africa, perhaps near the coast. They could have spread north as the lands recovered and their numbers increased.

It could be that in the years following the super volcano's eruption human groups that were near to each other worked together to improve their chances of surviving. These human groups could have taken the first steps toward forming social organizations that eventually became clans, tribes, and nations (in the modern era). Until that time, lacking agriculture and the means to grow food in large quantities, human groups would have had to remain small.

Research into the psychology of human relationships led Dr. Robin Dunbar to propose a practical limit to the number of relationships the modern human brain can manage: 148. Rounded up, this number has been called Dunbar's Number or the Monkeysphere. Dunbar's research suggests that -- depending on brain size -- animals can work together groups that have practical limits. Of course, social insects like ants and bees would seem to defy this principle but they are extremely alien to mammalian physiology. Among primates, the principle holds up well under close scrutiny.

In hunter-gatherer groups, for example, the maximum size is reached around 30-50 individuals (the same as among chimpanzees). If you add the ability for the group to obtain more food than hunter-gatherers normally can, the maximum group size increases to about 150. Sociologists point to Hutterite communities, which sub-divide after their populations exceed 150 because (the Hutterites say) their ability to control behavior through public shunning diminishes as the group grows beyond 150. The next larger division, requiring moderate social organization, achieves a range of between 500 and 2500 individuals. Dunbar calls these three groups bands, cultural lineage groups, and tribes.
I find it doubtful that actual tribes developed among ancient humans after the Topa Event but their clans (cultural lineage groups) may have been able to sustain themselves in coastal environments if the waters remained warm enough to support large numbers of fish and shellfish. In fact, Neanderthal diets were extensively dependent upon large game animals while early modern human diets included smaller animals, fish, and seafood. In a rich coastal environment, large numbers of early modern humans could have lived closer together and shared food resources when need arose.

This is a significant factor in social development, obviously, because as people live close together in larger numbers the potential for conflict and competition for resources arises. As the population of the coastal peoples increased they may have split off colony groups that emigrated northward, and yet those splinter groups may have stayed in contact with their parent groups for both social and economic reasons.