
Yes, as per The Secret of Our Success humans are very social creatures. But ultimately that sociality redounds to individual success (e.g., positional games/status hierarchies take up more time and energy than coordinating to achieve group success). Western civilization’s individualistic ethos is to my mind a reversion to a more primal norm, as dense human living became less constrained by the eternal Malthusian traps of the agrarian civilizations which arose after the Neolithic. Individualism and wealth go hand and hand.



Evolutionary processes in complexes species generally involves an element of intraspecific competition. Some would even posit that in many cases this is the dominant dynamic driving evolutionary change. But the invention of a caste of slaves, and masses of servile peasants, to serve a small elite, was a feature of agricultural civilization. This was no natural consequence of natural competition.
We know all this happened. The current project has to be to understand how it happened. Why it happened.
A new paper in Nature Genetics sheds light on a critical piece of the puzzle, Punctuated bursts in human male demography inferred from 1,244 worldwide Y-chromosome sequences. The figure below communicates the main results:
In some ways this seems an incremental improvement over last year’s A recent bottleneck of Y chromosome diversity coincides with a global change in culture. Much of the detail of this current paper, and why it adds to earlier work, can be found in the supplements.
The major takeaway is again you see evidence in Y chromosomal male lineages of incredibly rapid and explosive demographic growth. This is the rise of patriarchy, the arrival on the scene of despotic lineages which monopolized access to a disproportionate amount of the goods and services of many societies, including women.
In the plot above three lineages jump out at you. E1b, R1a, and R1b. The first is associated with the Bantu expansion, that occurred over the last 4,000 years. The second two are likely associated with Indo-Europeans in both Asia and Europe, respectively. The timescale is on the order of 4 to 5,000 years in the past. The association between culture and genes, or the genetic lineages of males, is rather clear, in these cases. In other instances the growth was more gradual. For example, the lineages likely associated with the first Neolithic pulses, J and G. Interestingly, the authors of the paper notice that the same is true in East Asia. Here one sees a more gradual accumulation of genetic mutations as lineages branch out from each other at a stolid pace, a sharp contrast to the explosive “star phylogeny” that is the case for R1b and R1a. This is almost certainly due to the differences in the cultural revolutions, and the reproductive success that that allowed a given male.
Finally, the authors suggest that haplogroup E, which is today the dominant lineage within Africa, though it is found in the Middle East and Europe, is the product of a back migration ~50,000 years ago. The argument is from parsimony. E and D are clearly a clade, and D is found in Japan (and also Tibet and Southeast Asia). If E originated in Africa, and later spread to Europe, so did D. Rather, the authors favor the model that E is a basal Eurasian haplogroup which percolated back into Sub-Saharan Africa during the Pleistocene. It would not be surprising that Southwest Eurasian humans would maintain contact with nearby African populations, but this sort of phenomenon does seem to point to the possibility for a Levantine origin for modern humans!
This is all based on contemporary DNA, and contemporary distributions of populations. There may have been mass extinctions which hide from our perception other demographic revolutions. Additionally, if there is one thing that ancient DNA has taught us, it is that modern distributions may not reflect ancient ones. Nevertheless, this is a good step in understanding the cultural changes which have resulted in the world we see around us.


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