Cultural complexity generated by mere numbers

And not any internal evolutionary change such as brain size or whatever.

Late Pleistocene Demography and the Appearance of Modern Human Behavior
Adam Powell, Stephen Shennan, Mark G. Thomas

The origins of modern human behavior are marked by increased symbolic and technological complexity in the archaeological record. In western Eurasia this transition, the Upper Paleolithic, occurred about 45,000 years ago, but many of its features appear transiently in southern Africa about 45,000 years earlier. We show that demography is a major determinant in the maintenance of cultural complexity and that variation in regional subpopulation density and/or migratory activity results in spatial structuring of cultural skill accumulation. Genetic estimates of regional population size over time show that densities in early Upper Paleolithic Europe were similar to those in sub-Saharan Africa when modern behavior first appeared. Demographic factors can thus explain geographic variation in the timing of the first appearance of modern behavior without invoking increased cognitive capacity.

Full article is behind paywall but you can read a press synthesis at Science Daily anyhow:

In the study, the UCL team found that complex skills learnt across generations can only be maintained when there is a critical level of interaction between people. Using computer simulations of social learning, they showed that high and low-skilled groups could coexist over long periods of time and that the degree of skill they maintained depended on local population density or the degree of migration between them. Using genetic estimates of population size in the past, the team went on to show that density was similar in sub-Saharan Africa, Europe and the Middle-East when modern behaviour first appeared in each of these regions. The paper also points to evidence that population density would have dropped for climatic reasons at the time when modern human behaviour temporarily disappeared in sub-Saharan Africa.

(...)

Dr Mark Thomas, UCL Genetics, Evolution and Environment, says: "When we think of how we came to be the sophisticated creatures we are, we often imagine some sudden critical change, a bit like when the black monolith appears in the film 2001: A Space Odyssey. In reality, there is no evidence of a big change in our biological makeup when we started behaving in an intelligent way. Our model can explain this even if our mental capacities are the same today as they were when we first originated as a species some 200,000 years ago.

"Ironically, our finding that successful innovation depends less on how smart you are than how connected you are seems as relevant today as it was 90,000 years ago."

This should be only so terribly obvious for us modern humans immersed in both high speed globalization and equally fast techno-cultural developement since some five centuries ago but still the monolith (i.e. the Judaistic myth of intelligence being a divine or otherwise extraterrestrial quality) remains stuck in our imaginary: we think of Paleolithic people as nearly chimpanzees who could not even light a fire (please!), when in truth they were just like you and me, just that their social-cultural enviroment was much more restricted: there were no public libraries back then, nor telephone, nor TV nor Internet: all knowledge was oral and you could only meet so many people in your life.

It seems that there were then some moments and places where population density thrived beyond what was normal for UP standards. This happened in Africa c. 100,000 years ago, when, coincident with a wet period, the first ornaments are found in almost identical styles from North to South of the continent. This happened in SW Europe through the Upper Paleolithic, notably Magdalenian, when cave art first appeared and reached heights that are still admired. And this happened in West Asia in the eve of Neolithic as well. And there are probably other cases as well.