Dawn of agriculture took toll on health
When populations around the globe started turning to agriculture around 10,000 years ago – regardless of location and type of crop – the height and health of people declined, probably because of an increase in disease and a rise in nutritional deficiencies. These are the findings of an Emory University team led by Amanda Mummert, who conducted a comprehensive review of studies on stature and health during the Agricultural Revolution. Results of the review will appear in Economics and Human Biology.
Mummert, an Emory graduate student in anthropology, said that agricultural settlements spurred population density, which led to an increase in infectious diseases, likely exacerbated by problems of sanitation and the proximity to domesticated animals and disease vectors (carriers).
This broad and consistent pattern holds up when you look at standardized studies of whole skeletons in populations.
Many people have this image of the rise of agriculture and the dawn of modern civilization, and they just assume that a more stable food source makes you healthier. But early agriculturalists experienced nutritional deficiencies and had a harder time adapting to stress, probably because they became dependent on particular food crops, rather than having a more significantly diverse diet.
Eventually, the trend toward shorter stature reversed, and average heights for most populations began to increase. The trend is most evident in the developed world during the past 75 years, following the industrialization of food systems.
Emory anthropologist George Armelagos, co-author of the review, said:
Culturally, we’re agricultural chauvinists. We tend to think that producing food is always beneficial, but the picture is much more complex than that. Humans paid a heavy biological cost for agriculture, especially when it came to the variety of nutrients. Even now, about 60 percent of our calories comes from corn, rice and wheat.
Armelagos, along with M. N. Cohen, wrote the book Paleopathology at the Origins of Agriculture, which drew from more than 20 studies to describe an increase in declining health and nutritional diseases as societies shifted from foraging to agriculture. The book was controversial when it was published in 1984, but the link between the agricultural transition and declining health soon became widely accepted in what was then the emerging field of bioarchaeology.
Mummert and her team undertook the current review to compare data from more recent studies involving different world regions, crops and cultures. The studies included populations from areas of China, Southeast Asia, Europe, and North and South America. These studies looked at entire skeletons and overall health, rather than focusing on particular skeletal elements and specific diseases.
Unless you’re considering a complete skeleton, you’re not getting a full picture of health. You could have an individual with perfect teeth, for example, but serious markers of infection elsewhere. You could see pitting on the skull, likely related to anemia or nutritional stress, but no marks at all on the long bones.
Adult height, dental cavities and abscesses, bone density and healed fractures are some of the markers used to paint a more complete picture of an individual’s health. Mummert said:
Bones are constantly remodeling themselves. Skeletons don’t necessarily tell you what people died of, but they can almost always give you a glimpse into their ability to adapt and survive.
Mummert said that it’s important to keep re-evaluating the data as more studies are completed. One confounding factor in conducting a study is that agriculture was not adopted in an identical fashion and time span across the globe. In some ancient societies, such as those of the North American coasts, crops may have merely supplemented a seafood diet. Mummert explained:
In these cases, a more sedentary lifestyle, and not necessarily agriculture, could have perpetuated decreased stature.
Some economists and other scientists are using the rapid physiological increases in human stature during the 20th century as a key indicator of better health. To this, Mummert added:
I think it’s important to consider what exactly “good health” means. The modernization and commercialization of food may be helping us by providing more calories, but those calories may not be good for us. You need calories to grow bones long, but you need rich nutrients to grow bones strong.
Bottom line: Amanda Mummert and her colleagues at Emory University conducted the first comprehensive review of studies pertaining to human health during the transition to agriculture worldwide. The team determined that the majority of studies show that human stature and health declined, probably due to an increase in disease and a rise in nutritional deficiencies. Results of the review will appear in Economics and Human Biology.