Monday, September 19, 2011

Migration 6: A Summary, and Some Conundra

Migration 6: A Summary; and some Conundrums 

Chris Stringer & Peter Andrews, "The Complete World of Human Evolution", 2005, provides a well-illustrated ride through the findings and ambiguities, telling me more and less than I want to know. Lots on apes and bones, but not on such as language, although it is called a defining characteristic that was likely not present early in our time.

As a leading proponent of the Out of Africa model of human spread, Stringer is of major importance for my picture of Homo sapiens as a species that moves, spreading out over the world, migrating. Interesting that when we use that word in reference to non-humans, we are describing repeating patterns, e.g., birds that fly south for the winter, and return north with spring. Human migration is, particularly by its opponents, on the other hand decried as a one-way flood. And of course, that is what the major debate among evolutionists is: what is the best model to describe how and when we got all over the world.

Here is their time-line for the model which has Homo sapiens developing from previous forms over about 400-150 Kya (thousands of years ago). About 160 Kya, we had spread throughout Africa, although much about that is "still tantalizingly unclear". Then, perhaps 100 Kya, we went across south Asia and to Australia by 60 Kya. Europe has evidence for 40 Kya, and the Americas, 15 Kya or even farther back. There are regional variations, with "relationships unclear". There was overlap with Neanderthals, who were throughout Europe, over to east of Caspian Sea. Did that overlap bring war, avoidance, coexistence, trade, interbreeding? Also "unclear:. Whatever, they were gone by 25 Kya. 

Humans, as CroMagnons in Europe, lasted for about 25 Ky, and seem to be almost the model type for Out-of-Africa people. They hunted, fished, traded, made art, recorded time, gathered plants, stored food, carried out ceremonies, and moved around a lot. They had a range of technologies, with quite swift development. Body size, as well as appearance, also could change in a few millennia.* Even with the addition of genetic analysis (of nuclear, Y chromosome, and mitochondrial DNA),  ambiguity exists as to whether humans moved into already vacated spaces or came into contact with other long-existing hominid species, and even interbred. 

We developed as fruit eaters, added meat, cooking it at some point -- according to Richard Wrangham maybe a very long time ago, though Stringer is not convinced. In their third section, Stringer & Andrews suggest 120 Kya for the start of the story of our spread, after a long time in Africa where we extended our range and adapted to climate change, and consequent changes in sea level, more than once. Again, they stress the data is sparse except for Europe. They suggest Australia by 50 Kya and China even before 30 Kya. It is all quite ambiguous, and no more so than for the Americas: 12 Kya? 20 Kya? with multiple waves of migration? (and that tradition continues, in fine, in the latest few hundred years of America). Perhaps this is a decent place to wonder about territoriality as an element in the make-up of a migratory species, whose travels spread over tens of millennia, which implies some periods of putting one's feet up for a while. 

They suggest there were universal activities, starting 75 Kya. Music, dance, painting, carving, pottery, weaving, social identity, ritual, trade. There was a tool-making change, using more non-stone, 40 Kya (Europe again): clay, rope, basketry. Personal ornaments, pigments, as well as art (>50 Kya in Europe?). There were camps with tents, hearths, & lamps using oil. And why is some cave art so hard to view? And how come most figurines are of women? Burials, because they constitute dramatic evidence, are an obvious object of study; are they earlier than 70 Kya? S & A suggest social stratification existed, based on the elaborateness of burial goods. And were there both female and male burials? They wonder about the meaning of child burials. And note that not all places have all elements of these widespread evidences, but all of this seems to add up to a coherent culture grappling with the world in a multi-faceted effort over the past 100 Ky.

For ambiguity, it is hard to beat evidences & argument on social organization. S & A start out with the other apes. Bonobos, closely related, are egalitarian, flexible, have female bonding, and large groups. Their temporary groups for foraging include males and all ages. S & A call this unique and rare. They prefer chimpanzee society as closer to ours: loosely coherent groups, coming together or not as need be. The core consists of male groups. Females go with kids, not the male groups. A flexible bunch.  Well, I am not going to argue that we are more bonobo than chimp, but in my reading of various of Stringer's works, his insistence on male-oriented monogamy as a genetically evolved trait is one that seems based on projection of how we are today rather than on the variety of human qualities evidenced.

S & A do say this: "it would certainly be unwise to assume that the social structures of today, which are often based on long-term pairing of males and females, had a long evolutionary history." They want to be cautious about comparing present-day hunter-gatherer groups for comparison, which seems wise. But then they say, "it seems unlikely that pre-modern humans had anything comparable" to any culture today as far as structure, language, and religion. Given that anything very recent has to contend with the influences from the Neolithic Revolution 15 Kya, that seems both likely and irrelevant for assessing how sophisticated a people we were from 100-15 Kya.

Finally, they get back to the "simple area" of the differences between males & females. Men can have many children, and women cannot. They also have to nurture children and go through menopause. THEREFORE, men are attracted to potential fertility, and women to men with stability and resources. This conclusion is one I have read in Stringer before; it was even less convincing, and S & A do say, genetic imperatives may not be the whole story; the environment matters. As will be evident from my previous posts, I think this is a grand misreading of how a small-band migratory species with language (and all its consequences) and our sexual characteristics operates. And in my next post, I want to make that case in more detail. 

For now, with all its ambiguities and unanswered conundra, there does seem to be this picture over, lets say 85 Ky, of a smallish population, lets say some tens of thousands in small mutually supportive groups, learning how to cope with changing environments by travel, technology, and culture, using its primary tool of language, a tool that through talk, thought, and imagination, brought greater and greater sophistication.

*This point on the swiftness (millennia) of evolutionary change of body size, is made by them in their section in The Book of Life (pp. 215-7) ed. S.J. Gould -- . 

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