We usually think of farmers as sturdy, Midwestern types who raise their ruddy-cheeked children on a balanced diet of eggs, potatoes, and chores. A study from researchers at Emory University, though, suggests that our farming ancestors weren't the picture of health. When humans transitioned from hunting and gathering to farming and living in cities, the authors say, they became malnourished and more prone to disease. Oh, and they were shorter.
Scientists use height as a rough yardstick of a population's health and nutrition. As an individual, your potential height comes from your parents' genes. But whether you reach that potential has to do with how healthy you are as a child--are you getting the right nutrients? Fighting diseases? And the average height of a population tells scientists roughly how healthy that population is. The tallest people on Earth today live in the Netherlands.
To assess the health of various prehistoric populations, the Emory researchers pooled data from several previous studies of ancient bones, then examined how people's heights changed as their populations transitioned to agriculture. Farming first appeared around 10,000 years ago in the Middle East, then spread around the globe, sometimes cropping up (ahem) independently. The populations included in this study ranged from 9,000-year-old Chinese to North Americans from within the past thousand years.
In general, the authors say, populations tended to get shorter as they transitioned from hunting and gathering to agriculture. Some bones provided evidence of malnutrition, anemia, and poor dental health. Why would farming make people sick? For one thing, relying on a smaller variety of food sources could lead to malnutrition, if crucial nutrients were missing from a farmed diet. Food supply depended on the seasons, and groups had to store enough food to last through the winter. A drought or infestation meant that the whole community went hungry. And since people were living in bigger, denser communities, infectious diseases could spread more easily.
The researchers acknowledge that several studies within the larger group they looked at did not find a short-farmer effect. Those studies found that height stayed the same, or even increased, when populations made the move to agriculture. The effect may have depended on the resources available in an area; maybe populations that could grow a greater variety of foods avoided a health decline. In some areas, height initially decreased but then increased over subsequent generations.
If farming were really a worse survival strategy than hunting and gathering, it couldn't have persisted. Rogue groups of humans who lived outside of the community and gathered their own food would have outcompeted their city-dwelling, farmer neighbors. Instead, farming became the norm. So this lifestyle--organizing ourselves into communities, sharing resources, dividing labor, domesticating crops and animals--must have provided a net gain in our well-being. Even if it initially made us a little more sickly, it allowed our populations to grow and spread.
You might interpret these findings as evidence that you should take up a "caveman diet." If so, there are plenty of books and websites out there to help you; they generally recommend starving yourself and eating a lot of nuts and meat. I'd recommend looking into local hunting laws before you start shooting your own squirrels and pigeons. (Of course, if you're on a true caveman diet, shooting is cheating.) This book even comes with a measurement conversion table, in case you're not sure how many ounces are in a skull cup.
Farming may be a relatively new development in human history, but that doesn't mean we're not built for it. For example, if your ancestors came from a dairying culture such as in northern Europe or eastern Africa, you probably drink milk and eat ice cream with no problem. This isn't the caveman way. For our ancient ancestors--as it is for humans in most parts of the world today--the enzyme that breaks down the sugar in milk (lactose is the sugar, lactase is the enzyme) faded away as humans grew out of early childhood. But the tendency to hang on to lactase has evolved at least twice since we started keeping dairy animals. Drinking a domestic animal's milk must have given these populations a serious evolutionary advantage in order for the lactase-keeping trait to spread so well. So is it "unnatural" to drink milk as an adult? My genes say no, though yours might say something different. It's not the caveman way. But we're not cavemen anymore; we're farmers.
Mummert, A., Esche, E., Robinson, J., & Armelagos, G. (2011). Stature and robusticity during the agricultural transition: Evidence from the bioarchaeological record Economics & Human Biology, 9 (3), 284-301 DOI: 10.1016/j.ehb.2011.03.004
Botany 2015 -Monday
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