One thing I love about Cultural Evolution is how it makes us look at ordinary things we do every day from a completely new angle. As an example, if you think about it, wearing pants, especially in warmer climates, is a very strange thing. It turns that there is a surprising explanation why we do it (check my posts on The Evolution of Pants).
Similarly, some characteristics of our modern societies are actually a result of decisions made by our distant ancestors thousands of years ago. Take the domestication of plants—this was one of the most momentous decisions made by humans, which enabled cities and civilization, sciences and arts, modern government and warfare, and many other things, good and bad.
So much is well known. What is less known is that a choice of particular cultivar can have unexpected and profound consequences down the line.
Consider China. In the cooler and drier north the grains that were domesticated included first millet and later wheat. In the hot and humid south, the grain of choice became rice.
Wheat and rice require very different cultivation methods that actually shape societal institutions. Paddy rice cultivation requires massive labor inputs, which are, however, limited in time. Labor requirements are so high that a single family cannot do it. So what rice farmers do is that several families cooperate. They stagger planting times in such a way that they all first take care of one family’s farm, then go to the next, and so on.
Growing wheat, on the other hand, doesn’t require such collective effort. A family can take care of its farm by spreading the work over a longer period of time.
Different cultivars require different technologies to grow; not just agricultural, but also social technologies—institutions. And these institutions left a long-lasting imprint on people’s psychology. A recent study in Science by Thomas Talhelm and coworkers found that people from rice-growing counties were more interdependent, collectivist, and holistic thinking than people in wheat-growing counties. Note, experimental subjects tested by Talhelm et al were not farmers; they simply grew up in local societies whose institutions and even ways of processing information co-evolved with subsistence technologies in the past.
In the psychological test illustrated below, people from rice-growing regions chose holistic answers; those from wheat-growing regions chose analytical answers.
Measuring analytical versus holistic thinking. From Henrich, Joseph. 2014. Rice, Psychology, and Innovation. Science 344:593-594.
And this is not all. Rice versus wheat agriculture affects not only psychology, it affects health. That was literally a life-and-death decision that the early adopters of plant cultivars made for their descendants.
In an article that was published in the last issue of Cliodynamics: The Journal of Quantitative History and Cultural Evolution, Ned Kock, an economist at the Texas A&M University, analyzes the China II data on diet and mortality in 69 counties of China (between 1983 and 1993). Kock found that as the proportion of wheat in diet increased, so did mortality from vascular disease, such as heart attacks and stroke:
As diet shifts from completely rice-based to completely wheat-based, heart-disease mortality increases by 50 percent! That’s a huge effect.
A very interesting question, of course, is what it is about wheat that is so lethal. Because we have only correlational data (so far), any conclusions must be speculative. Ned Kock thinks that
it may not be wheat flour consumption that is the problem, but the culture associated with it, which is characterized by decreased levels of physical activity, decreased exposure to sunlight, increased consumption of processed foods, and increased social isolation. Wheat flour consumption may act as a proxy for the extent to which this culture is expressed in a population.
Note that “increased social isolation” is an aspect of more individualistic, and less collectivist culture of wheat regions. This could be a contributing factor.
Yet, readers of my blog would probably guess that, unlike Kock, I would place blame squarely on wheat. Simply put, wheat is a much more poisonous grain than rice. Especially if you consume polished white rice because most of the toxins that rice uses to deter herbivory are located in the brown skin of the rice grain. I have asked Paul Jaminet, the author of the Perfect Health Diet to comment on Ned’s article, and I hope this comment will be published in the next issue of Cliodynamics. So more is to follow.