One of the most persistent debates about the process of evolution is whether it exhibits directionality or inevitability. This is not limited to a biological context; Marxist thinkers long promoted a model of long-term social determinism whereby human groups progressed through a sequence of modes of production. Such an assumption is not limited to Marxists. William H. McNeill observes the trend toward greater complexity and robusticity of civilization in The Human Web, while Ray Huang documents the same on a smaller scale in China: A Macrohistory. A superficial familiarity with the dynastic cycles which recurred over the history of Imperial China immediately yields the observation that the interregnums between distinct Mandates of Heaven became progressively less chaotic and lengthy. But set against this larger trend are the small cycles of rise and fall and rise. Consider the complexity and economies of scale of the late Roman Empire, whose crash in material terms is copiously documented in The Fall of Rome: And the End of Civilization. It is arguable that it took nearly eight centuries for European civilization to match the vigor and sophistication of the Roman Empire after its collapse as a unitary entity in the 5th century (though some claim that Europeans did not match Roman civilization until the early modern period, after the Renaissance).
It is natural and unsurprising that the same sort of disputes which have plagued the scholarship of human history are also endemic to a historical science like evolutionary biology. Stephen Jay Gould famously asserted that evolutionary outcomes are highly contingent. Richard Dawkins disagrees. Here is a passage from The Ancestor’s Tale:
…I have long wondered whether the hectoring orthodoxy of contingency might have gone too far. My review of Gould’s Full House (reprinted in A Devil’s Chaplain) defended the popular notion of progress in evolution: not progress towards humanity – Darwin forend! – but progress in directions that are at least predictable enough to justify the word. As I shall argue in a moment, the cumulative build-up of compelx adaptations like eyes strongly suggest a version of progress – especially when coupled in imagination with of the wonderful products of convergent evolution.
A few days ago I was listening to an interview with a reporter who was kidnapped in the tribal areas of Pakistan (he eventually escaped). Because he was a Westerner he mentioned offhand that to “pass” as a native for his own safety he had his guides claim he was Nuristani when inquiries were made. The Nuristanis are an isolated group in Afghanistan notable for having relatively fair features. His giveaway to his eventual captors was that his accent was clearly not Nuristani, and master logicians that the Taliban are, the inference was made that he was likely a European pretending to be Nuristani.
I thought about this incident when looking over the supplements yesterday of Reconstructing Indian population history. On page 19 note S2 figure 1 includes the Kalash of Pakistan. These are the unconverted cousins of the Nuristanis who were not forcibly brought into the religion of peace in the late 1800s because their region of the Hindu Kush was under British rule, who naturally imposed their late 19th century European value that populations should not be converted by force to a particular religion (Nuristan means “land of light,” whereas before Afghans called it Kafiristan, “land of the unbelievers”). Despite the fair features of the Kalash, which has given rise to rumors that they are the descendants of Alexander the Great’s soldiers, they cluster with Central and South Asian populations, not Europeans. Like the Ainu of Japan it seems superficial similarities to Europeans, at least in relation to the majority population around them, has resulted in an inordinate expectation of total genome exoticism, when in reality a few particular loci are producing the distinctiveness.
Figure 1 from the 2007 paper, Genetic Evidence for the Convergent Evolution of Light Skin in Europeans and East Asians, brings home the point: