Last week, the New York Times ran a profile of economist Robert Fogel in anticipation of the release of the book The Changing Body: Health, Nutrition, and Human Development in the Western World since 1700, of which Fogel is a co-author. During his career, Fogel and his colleagues have amassed a mound of evidence on the shape and size of the human body and how this has changed over the last few hundred years. I have not read much of Fogel’s work before, but the book looks like it is worth a look.
The key theme from Fogel’s data is that there have been significant gains in height and mass as countries develop. As the Times states:
To take just a few examples, the average adult man in 1850 in America stood about 5 feet 7 inches and weighed about 146 pounds; someone born then was expected to live until about 45. In the 1980s the typical man in his early 30s was about 5 feet 10 inches tall, weighed about 174 pounds and was likely to pass his 75th birthday.
Across the Atlantic, at the time of the French Revolution, a 30-something Frenchman weighed about 110 pounds, compared with 170 pounds now. And in Norway an average 22-year-old man was about 5 ½ inches taller at the end of the 20th century (5 feet 10.7 inches) than in the middle of the 18th century (5 feet 5.2 inches).
This rate of change over the last few hundred years is much higher than that of the previous millennia.
The Times talks of how “technology has sped human evolution”, although this is not evolution as biologists would call it. Fogel infers no change in underlying genotype. Rather, Fogel calls it “technophysio evolution”, and it provides one of the strongest illustrations of environmental effects on phenotype. Technophysio evolution includes changes due to the womb environment, so might be considered to include epigenetics.
Having said that, this is another area where we should not ignore evolution in the biological or genetic sense. As much of Fogel’s work details, Americans around the time of the civil war were surprisingly sick, and were often ill from a young age. While improvements in environment have been responsible for much (or most) of the improvement in health and increase in body stature, there would also have been strong selection pressures on people at this time. While I am not hugely familiar with the literature, I would expect that there would be some differences in fertility by stature (as John Hawks suggests here). Three hundred years is enough time for genetic changes to have occurred.
Genetic considerations are also relevant to some of the debates about the meaning of Fogel’s results. For example, the Times quotes Angus Deaton, who is sceptical about some of the conclusions on height, and in particular, he questions whether they should be attributed mainly to nutrition. Deaton states that:
We don’t really understand why African adults and children are so much taller than Indian adults and children, but it can’t be their income, because Indians are much richer.
Is this missing the obvious genetic explanation?
Having said that we should not ignore evolutionary factors, stature information is still a useful indicator of development. If height in a developing country is stagnant or decreasing, it is a solid signal that living conditions are not improving. But, if height differences between countries persist despite income increases, consideration of genetics might allow us to stop worrying that everyone is not the same height.