On several occasions, when I presented the results of our model and data analysis that support the idea that the primary engine of the evolution of large-scale states is warfare, people objected by saying that there are lots of places on earth where warfare is very intense, but no states formed. One of the most frequently mentioned (supposed) counter-examples is New Guinea.
Indeed, New Guinea looks like an anomaly from the point of view of several theories. The most recent archaeological data suggest that agriculture in New Guinea is almost as old as in the Fertile Crescent. So, according to Jared Diamond’s theory in Guns, Germs, and Steel, New Guinea should have had large-scale complex societies long ago.
Warfare is very intense, as we saw in my previous blog. According to Mervin Meggitt’s estimate, 35% of Mae Enga men die of war-related causes. Even more important, group extinction rates are very high.
In an influential paper, Can group-functional behaviors evolve by cultural group selection? An empirical test, published in 1995 in Current Anthropology, Joseph Soltis, Robert Boyd, and Peter Richerson summarized the evidence for cultural group extinction rates in New Guinea. The Mae Enga was one of their strongest case-studies. Using Meggitt’s data, they calculated that 18 percent of Mae Enga clans go extinct in one generation (25 years). A typical extinction event happens when a clan loses war to a neighbor, resulting in most of the clan members dispersing and joining other clans where they have relatives. Clan extinction is quite common in other New Guinean ethnic groups, with per-generation extinction rates ranging from 1.6 to 31.3%, and the median rate of 16.7%.
But high clan extinction in New Guinea coexists with low rate of cultural group extinction. It’s all a matter of social scale. Clans are very small-scale groups.
An ethnolinguistic group in New Guinea, such as the Enga, may have several dialectal groups, such as the Mae Enga. The next level is tribes or phratries, and the lowest level is the clans. So there can be a high turn-over at the level of the clans, but a much lower turn-over at the level of phratries, and very slow turn-over at the level of dialectal or linguistic groups.
And cultural group extinction, at the level of ethno-linguistic groups, is veeery slow in New Guinea. This island contains an astounding number of languages—more than 1000. High linguistic diversity means that cultural group extinction is rare; it is a sign of weak competition between ethnolinguistic groups. So intense between-clan warfare is within ethnolinguistic groups, not between them.
High linguistic diversity is found in two kinds of terrain: in areas overgrown by thick and impenetrable tropical forests and in mountainous regions. The tropical island of New Guinea has both the extremely rugged mountains and dense vegetation (where it is not cleared for growing plants). Other mountainous areas that have very high linguistic diversity are the uplands of South-East Asia and the Caucuses mountains.
Historical linguists refer to mountainous areas in which languages of various families have been preserved, such as New Guinea and the Caucasus, as “residual zones.” A “spread zone,” in contrast, is an area where languages tend to spread out widely, driving previous languages in the area to extinction. A typical result of a spread is that only one language occupies most or all of the area. Spread zones, are thus, regions where competition between cultural groups is so intense, that one particular linguistic group can drive many others to extinction over a large area.
It should not come as a surprise that broad treeless flatlands, such as the Great Eurasian Steppe, or the North American Great Plains, are spread zones. We know enough history of the Eurasian Steppe to actually time some of the great spreads that swept literally across thousands of kilometers between what is now Ukraine and Mongolia. These highly successful groups include such speakers of Iranian languages as Medians, Persians, and Scythians or Sakas three millennia ago. These ancient peoples were succeeded by the Turkic and Mongolic nomads who spread from East to West in the Middle Ages. Finally, the Russians spread East along the northern edge of the Great Steppe during the Early Modern era. As a result, practically everybody who lives within the steppe belt of Eurasia speaks one of the languages spoken by these peoples, or its descendant.
So here’s my solution to the New Guinea puzzle. Warfare there is very intense, but because of the terrain it occurs at a very small social scale. As a result, cultural group selection is very weak, and we wouldn’t expect cultural evolution to larger-scale societies. From the point of view of cultural multilevel selection, New Guinean warfare is completely counter-productive.