19 May 11 Humans “supersize” as technology advances our evolution
For nearly three decades, the Nobel Prize-winning economist Robert W Fogel and a small clutch of colleagues have assiduously researched what the size and shape of the human body say about economic and social changes throughout history, and vice versa. Their research has spawned not only a new branch of historical study but also a provocative theory that technology has sped human evolution in an unprecedented way during the past century.
Next month Cambridge University Press will publish the capstone of this inquiry, “The Changing Body: Health, Nutrition, and Human Development in the Western World Since 1700”, just a few weeks shy of Fogel’s 85th birthday. The book, which sums up the work of dozens of researchers on one of the most ambitious projects undertaken in economic history, is sure to renew debates over Fogel’s groundbreaking theories about what some regard as the most significant development in humanity’s long history.
Fogel and his co-authors, Roderick Floud, Bernard Harris and Sok Chul Hong, maintain that “in most if not quite all parts of the world, the size, shape and longevity of the human body have changed more substantially, and much more rapidly, during the past three centuries than over many previous millennia.” What’s more, they write, this alteration has come about within a time frame that is “minutely short by the standards of Darwinian evolution.”
“The rate of technological and human physiological change in the 20th century has been remarkable,” Fogel said in an interview with the New York Times from Chicago, where he is the director of the Center for Population Economics at the University of Chicago’s business school. “Beyond that, a synergy between the improved technology and physiology is more than the simple addition of the two.”
This “technophysio evolution,” powered by advances in food production and public health, has so outpaced traditional evolution, the authors argue, that people today stand apart not just from every other species, but from all previous generations of Homo sapiens as well.
“I don’t know that there is a bigger story in human history than the improvements in health, which include height, weight, disability and longevity,” said Samuel H Preston, one of the world’s leading demographers and a sociologist at the University of Pennsylvania. Without the 20th century’s improvements in nutrition, sanitation and medicine, only half of the current American population would be alive today, he said.
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).
Fogel (left) and his colleagues’ great achievement was to figure out a way to measure some of that gain in body size, Preston said. Much of the evidence — childhood growth, mortality, adult living standards, labour productivity, food and manufacturing output — was available, but no one had put it all together in this way before.
Over the years Fogel and his colleagues have pored over a monumental amount of raw data to piece together the health records of thousands of people in different countries. When he won the Nobel in economics in 1993, the Swedish committee stated it was “for having renewed research in economic history by applying economic theory and quantitative methods in order to explain economic and institutional change.”
“The Changing Body” is full of statistical tables and graphs that include the heights of girls in Croatia and Germany; the caloric energy derived from potatoes, fish and wine; and the average annual allowance of grains and meat for widows in Middlesex County, Mass, from 1654 to 1799 — a testament to both the staggering accumulation of information and the collaborative nature of the enterprise.
But the basic argument is rather simple: that the health and nutrition of pregnant mothers and their children contribute to the strength and longevity of the next generation. If babies are deprived of sufficient nutrition in the womb and early in life, they will be more fragile and more vulnerable to diseases later on. These weakened adults will, in turn, produce weaker offspring in a self-reinforcing spiral.
Technology rescued humankind from centuries of physical maladies and malnutrition, Fogel argues. Before the 19th century, most people were caught in an endless cycle of subsistence farming. A colonial-era farmer, for example, worked about 78 hours during a five-and-a-half-day week. People needed more food to grow and gain strength, but they were unable to produce more food without being stronger.
The new book is not yet available, but experts familiar with Fogel’s work say that disagreements have arisen over his explanations for improved health in the West. Preston agrees that technology has superpowered human evolution over the past hundred years, but in his view the prevention of infectious diseases has not received sufficient credit.
“In many parts of the world, including the United States in the 20th century, medical advances appear to be at least as important as improvements in nutritional intake,” he said.
Preston pointed in particular to public health practices — like protecting water supplies, installing sewage systems and hand washing and quarantining in hospitals — that were instituted in American cities, beginning in the 1890s. An infinite supply of food is irrelevant, for example, if you can’t prevent chronic childhood diarrhea. Height dipped in the late 18th century when poor sanitation and infectious diseases plagued crowded new cities.
Angus Deaton, an economist at Princeton University who researches health in rich and poor countries, says he admires Fogel’s work as well, but he too is skeptical about the emphasis on nutrition, as well as about some of the conclusions researchers have inferred from height.
“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,” he said. India has twice the per capita income of Kenya and about three times that of Tanzania.
Fogel’s work could have significant consequences for determining policies for the developing world. Recdently, researchers at the Harvard School of Public Health published a paper that used the height of women in 54 low- and middle-income countries to indicate how children in Africa, Latin America, Asia and the Middle East were faring. (The answer was not good: height had stayed the same or declined, particularly in Africa, suggesting that living conditions and disease controls for children have deteriorated.)
The best way to combat such decline depends on the cause-and-effect relationships among economic growth, nutrition and health, Mr. Deaton said. If food production is the most important factor, then focusing on economic growth might be the best policy, but if infectious disease is a major reason for chronic illness and premature death, then more aggressive public health measures might also be needed.
To Carole Shammas, an expert in socioeconomic history at the University of Southern California, the problem in her field is that historians have not paid enough attention to changes in height (as a useful measure of nutrition and disease) or in lifespan. History textbooks, she complained, almost completely ignore the topic.
One thing Fogel did not expect when he first started his research was that “overnutrition” would become the primary health problem in the United States and other Western nations. Obesity, which increases the risk of heart disease, stroke, hypertension and some cancers, threatens to upset the links in the upward march of size, health and longevity that he and his colleagues have spent years documenting.
But Fogel said that he remained an optimist at heart. The human body is enormously flexible and responsive, he said, a fact that fills him with confidence that “the trend of larger bodies and longer lives will continue into the future.”
Source: NY Times
Read more on the debate on this issue: Do We Want to Be Supersize Humans? If human bodies become taller, bigger and longer-living – is that progress?