Scientists Continue Exploring Africa’s Age of Adam

In a lengthy discussion titled Africa 60,000 Years Ago: The Age of Adam SF-Fandom founder Michael Martinez proposed an interpretative reading of a growing body of signals from the past 30-120,000 years of human existence in and near Africa.

DNA sampling suggests that all modern humans may be descended in the male line from an “Adam” who lived in southern Africa about 60,000 years ago (although mitochondrial DNA suggests that our most recent common female ancestor lived about 200,000 years ago).

The strong implication is that many male lines of descent have died out through the millennia for reasons we have yet to determine. Males may have been killed off in ancient clan warfare we cannot yet point to, for example.

A recent study of four male DNA lines suggests that modern human populations outside of Africa may have suffered a 90% decline over a 20,000 year period beginning around 80,000 years ago — and that these extra-Africanic populations may have interbred with Africans over that 20,000 year period.

One of the dividing lines of geological history in the 20,000 year period in question is the Toba event — a huge volcanic eruption believed to have occurred between 69,000 and 77,000 years ago. This event — some scientists say — may have reduced modern human populations to about 10,000 individuals, perhaps all living in Africa at the time (the volcano erupted in what is now Lake Toba in Sumatra, Indonesia).

The Toba event may have created an opportunity for one male line to exterminate other male lines in a spiraling process of clan conflict that pushed outward from Africa. There would have been too few people to develop into any sort of tribal society but small clans might have pushed outward from a relatively narrow region, gradually absorbing female DNA lines into the new human collective.

These clans would have inherited a tradition of communication and trade with other clan groups — practices that have been verified going back at least as far as 100,000 and perhaps 120,000 years. We cannot be sure of why people would have returned to Africa, but we can make some guesses.

For example, defeated clans on the fringe of Adamic groups’ expansion might have been pushed back and forced to retreat through lands controlled by other clans.

Or it could be that clans sent young males on quests back to the ancestral lands. Some might have chosen to stay in Africa.

It could also be that localized disasters forced family groups to migrate back toward Africa.

It might also be that conflicts between emigrating groups and older groups of humans in Europe and Asia led to infanticide of daughters, or simply a preponderance of males over females as women and girls died off. Hence, young men might have undertaken vast journeys to find mates.

We assume a minimum degree of social sophistication among these peoples because there is no evidence to show that they built complex societies. But it is entirely possible that the complex society consisted of a network of families and small clans who were aware of their common origin and who practiced pilgrimages back to the land of the ancestors.

Some pilgrims might have remained in the ancient lands. It could also be that outcasts from small community groups were forced to seek new lives far from the peoples who might know of their transgressions.

What we can be sure of is that there was indeed significant overland travel around the time of 60,000 years ago — that there was trade between distant groups — and that the travel of individuals probably passed both into and out of Africa, leading to a mixing of male lines of descent.

What we cannot be sure of is whether there was a common factor that contributed to the significance of the Adamic male line. Did they simply have numbers on their side? Were they more immune to some disease? Were they better equipped with superior weapons and tools? Did they preserve a communal knowledge of hunting or warfare that gave them an advantage over groups that had left Africa in earlier generations? Did they take greater risks, perhaps breed more children with the intention of spreading outward?

So-called hunter-gatherer cultures developed semi-permanent structures, sophisticated production of food and other resources from game and foraging. They would have had the time on their hands to think about what lay beyond the next hill. It could be that while most populations struggled to survive an abundance of resources in south and central Africa produced a continually booming population.

We have only begun to study this interesting period in human experience. Much remains to be discovered, analyzed, and understood. It may be that we’ll have to re-assess our ideas of what modern humans were really like 50,000 years ago. It should be fun.