Nov 7, 2018 11: 50 pm
Individual and group survival, was enhanced by a steadier food supply; indeed a new degree of coordinated meat provisioning, that was calculated over a period of weeks (rather than one-hunt-at-a-time), may have been a major advantage of the Homo sapiens culture that developed in the larger refuge areas along the eastern and south African coast and river deltas. This was plausibly enhanced when it incorporated the use of aquatic and marine resources as well. Each hunter going forth in a different direction would almost guarantee at least some fish, or game, meat several times a week.
Thus, the changed technologies of the MSA in Africa plausibly represented a safer, and more efficient use of hunting labour. In turn this may have increased childhood survival rates and led to the modest rates of population growth we see even today among hunter-gatherers even in the harshest environments. We might expect to see evidence gradually starting to grow more quickly, in hunter-gatherer sites.
The complete package of Middle Stone Age technologies were essentially markers for a cultural transformation that permitted a more successful hunter-gatherer economy. As these behaviours spread all around the African coastlines, despite on-going climatic fluctuation and hardship population growth seems to have increased. Current data on hunter-gatherers suggest population growth rates averaging 0.05% a year – which seems low by today’s standards of comparison, but it seems to have been relatively higher than that of archaic Homo sapiens. Even increasing it to this modest rate produces a doubling time of roughly 1400 years. From a starting point somewhere in the eastern African coast, and even starting with very low numbers of people involved in the initial group(s) that trickled into Eurasia, this is sufficient to reach Australia within 15,000 years, purely as a function of normal population growth along the coast. (Doubling time is calculated by the formula: Td = log(2) / log(1 + r) Where: Td = doubling time and r = a constant growth rate)
When representatives of this culture, propelled simply by this modest rate of growth, expanded throughout the rest of Africa, as well as throughout Eurasia, and encountered other, more “archaic” people, it is possible that they passed on practical concepts and technical elements. This, very plausibly, consolidated the patterns already in play among these other communities as well. Furthermore, as this gradually spread I would suggest that the exchange of information and materials to the next group and the next, even over vast distances, gradually started that same altered selective process in the anatomy of these other groups. This would have taken thousands of years to have a visible effect on skeletons, but we know now that this process literally had thousands of years: in Africa it had at least 100,000 years and possibly even longer.
I might add that by intermarrying with other groups, “anatomically modern” humans increased their own genetic diversity, even if it occasionally meant importing some problematical recessive alleles. At the same time, they were living demonstrations of a successful economic pattern. Indeed, as these technologies and practices permitted population growth, the tendency would have been to increase the flow of information and personnel in both directions. This would have happened each time this culture come into contact with others all over Africa, and it also happened between groups that had trickled into Eurasia.
The genetic data appears consistent with all anatomically modern humans alive today stemming mainly from one ancestral culture area within Africa. This was most likely to have been one of a series of interconnect cultures developing along the coasts of the entire continent. Especially during the height of inland mega droughts, even at very slow rates of population growth (.01% a year) archaic Homo sapiens could still have eventually spread south toward the Cape as well as north past the Horn and up major rivers such as the Nile, and around the shores of the Mediterranean, as well as across southern Arabia towards the Tigris, and the Euphrates and onward. These people would, of course, neither be aware of leaving one continent and entering another. I doubt they were even likely have completely lost touch with the communities their ancestors had come from. It seems probable that many would have developed rafting and even boats from time to time, to explore offshore islands, and to cross deeper stretches of water. Such a culture would have developed exploiting several ecological zones. They could supplement the dwindling savanna with near-shore aquatic resources, as well marine resources like shellfish, fish, and sea-going mammals.
Possibly, this culture area represented a set of linked demes speaking an array of dialects. I think it is plausible that the people in these remained intermittently interconnected by networking ties that permitted a flow of information and personnel. People in the coastal culture area less fragmented by these droughts would have been the likeliest candidates to become the first to pull all the strategies of ecological engineering together. Once this happened, this would furthermore be the one linked “culture area” capable of budding new communities up and down the coasts rivers even in the worst times of drought and hardship.
It is astonishing to realize that people likely did not have a goal of “leaving Africa”; rather, in the process of doubling every 1400 years would still fill up the world, NO ONE need ever have moved more than a few hundred miles, in a whole lifetime.
Try the calculation.
a) Assume a SE African culture area of hunter-gatherers who occupied the savanna and coastal region. Around, let us say, 90,000 years ago, a small daughter colony of this coastal culture has been established here and there “outside of Africa” – 1000 people scattered in 40 camps along the eastern Mediterranean coast, 1000 people scattered in 40 camps in the southern Arabian peninsula. There is some archaeological evidence of this, although at a slightly later date.
Note: I am assuming a set of demographic units that range over a territory of about 8,000 to 12,000 square km, a pretty average figure for a mobile hunter-gatherer group of about a thousand. Since they have a riparian, lacustrine, or coastal adaptation with some inland hunting, one can imagine an elongated territory stretching 200 kilometres along the lake shore, the coast, or the river, augmented by gathering and hunting resources perhaps 50 kilometres inland. Both of these would be, in our OOA model, derived from one of the northernmost groups of the chain of African cultures which appear to have had this dual ecosystem adaptation – using the aquatic as well as terrestrial resources, as well as the rich mixture of both represented by river deltas.
b) So we assume a starting population in the Middle East and along the south coast of Arabia of 2000 people. Now let us calculate how many there would be, at the modest rate of 0.05% increase per year, after 10 to 12,000 years.
After 1400 years, it is 4000, after another 1400 years, it is 8000, then 16,000, then 32,000, then 64,000, then 128,000, then 256,000, then 512,000, then 1,024,000 – and it is only 67,400 years ago.
c) Over a million people in Eurasia within about 12,000 years. Even if we assume all kinds of setbacks through diseases and adverse climatic events, and double that time, there could still be still be nearly a million Homo sapiens in Eurasia within a very short time. Does this make the genetic data that supports the idea of “out of Africa” more plausible? I doubt was as neat as this, but the exponential function is relentless. One way or another, our hunter-gatherer ancestors were pretty successful, not just in Africa, but all over the world.
We could change the starting date.. make it 100,000 or 50,000 years ago. But the main point here is that, no matter when we start the clock, there would still be over a million modern Homo sapiens in Eurasia within 12,000 years, for example, and it would be two million 1400 years later.
Given the shorter doubling times that prevail in modern Homo sapiens (at least until the annual rate of population increases was further raised by improved sanitation, medical care, antibiotics, vaccines, and so on) it really did not take repeated “waves of migration” out of Africa to populate the world.
A little squirt across the Red Sea, mission accomplished. Nor did the ancestral roll call of anatomically modern people have been lengthy even in Africa. It was obviously a longer roll call – the population remaining in Africa was likely at least ten times larger: most genetic variation was left behind. But we can easily derive various calculations, from a starting population as small as 20,000 or 30,000, and fill up all of Africa remarkably quickly, and test the plausibility of how modern humans enveloped and absorbed, both genetically and culturally, most of the “archaic” populations they encountered in the process.
All in all, I think what was “special” about the generalist hunter-gatherers with modern anatomy was indeed, a new ecological niche. But it was not because we became a new kind of biological animal, it was because we doubled down on what humans were, and still are, really good at adapting through feedback between culture and biology.
Developing a highly durable cultural system, one that manipulated whole ecosystems, was doing something new, ecologically. Despite evidence of use of fire for cooking and modification of material technology dating back at least two million years, no previous humans used fire ecology, or deliberately replanted, to promote plants and animals that they liked to eat. They may have had division of labour, but not the level of specialization in economic activities and conceptual realms common among hunter-gatherers today. You find quirky tinkerers as well as obsessive geniuses among all modern humans. I think cognitive variability may be a necessary and biological consequence of the kind of genome that can actually support long term investment in culture as a main adaptive strategy. Of course these kinds of minds are but leavening: for human culture to work, you also need a solid doughy lump of retentive rationality.
Even if only a tiny minority of people in any deme pondered particular issues and came up with wild ideas as well as practical innovations, any real conceptual breakthroughs, and resulting practices, could be demonstrated to others. The successful application of concepts generally is what reinforces their utility. Thus, even when few people in the rest of the culture actually understand the causal relationships, they can still make use of the resulting practical ideas. Any culture can change successfully as long as a sufficient minority of observers ponder and tinker with materials and ideas exist within them, and such people are indulged – or at least, given an audience and a fair opportunity to show how their discoveries work. In the later Pleistocene, when people were coping with extremes of fire and ice, receptivity to new technologies and ideas must have peaked at times.
I find it significant that all the survivors, of this exercise in cognitive shape-shifting, appear to be the anatomically modern human beings we identify today as “ourselves”.
Is it plausible, then, that the absorption of any remaining “archaic” people was as much cultural as biological? Why not consider a model of intermarriage, not “interbreeding”? Why not envisage the children of unions between these “archaic” and “modern” people being raised by their parents and grandparents, speaking two or more languages? Why not explore the implication that these children, although showing more robust anatomy initially, would be leaving descendants who were more and more anatomically “modern” as time went on, transformed by the elixir of humanity’s cleverest culture: the one that gardened Eden?
The ecological engineering associated with these early “hyper-keystone” human economies represents the single most successful collective cognitive niche that humans ever developed.
Sadly, today, only a small number of humans on the planet still know how to do this.
I wonder if Woodstock got this one right – maybe we really must get back to the garden, before our current global civilization foolishly undoes what took thousands of years of observation, empiricism, work, and passion, to create.