Europeans, in other words, seem to have sustained a more luxuriant growth of autonomous private groups than other societies did. The plow team was probably the cell from which this capability grew. Travelers may notice that people in those parts of Europe where cooperative moldboard plowing once prevailed still obey rules, form queues, and in general trust one another more than do the inhabitants of land where separate families cultivated their fields independently and often distrusted their neighbors because of boundary disputes or the like.In other words, if you weren't a polite team player in moldboard plowing lands, you were ostracized: you wouldn't be able to grow as much stuff as others (if any at all), which had a huge fitness impact during this time period, as the end of the Medieval Warm Period and the Black Death made it difficult to scrape by even with teamwork. Throughout this book, the authors waffle w.r.t. Darwinian selection as opposed to cultural selection, though I remember reading a parenthetical remark which showed they're not opposed to the notion of recent natural selection in humans. And given the papers that've been coming out on this topic over the past year (which I wrote about here and here), the idea has even more support.
I mention this because I wonder whether it will be important in determining which part of the globe will make the most impressive breakthroughs on recent selection in humans. So far the Americans have been ahead, though the data are drawn from among the three major racial groups, rather than from within, say, Europe, where regional differences and recent history are better understood. Indeed, Europeans can't help but notice national differences in personality, as when a Briton visits Spain or Italy and is perplexed by the local lack of queue-forming ability. Now, we Americans notice even greater differences between the various races that make up our country, but this is less PC to investigate, whereas using molecular and cultural data to test hypotheses about what makes the Mediterraneans (compared to Nordics) more extroverted, queue-deficient, and attractive -- while anathema to the EU's axiom of national sameness -- isn't so offensive to the general intellectual culture. Could they be the wedge?