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Growing crops made us smaller


When humans first started to farm, we became shorter and less healthy. The effect didn't last forever, especially in the developed world following the industrialization of food systems, the researchers say. Shown here are wheat fields in eastern Washington.

People got shorter and sicker everywhere in the world when they started to farm, according to a recent study that suggests the transition to an agricultural lifestyle came at a biological cost.

The transition occurred at different times in different places around the world beginning about 10,000 years ago in the Fertile Crescent, an arc of land spanning modern day Egypt to the border between Iraq and Iran.

As people gave up the diverse diet of foraged foods and settled on eating a few staple food crops they "experienced nutritional deficiencies and had a harder time adapting to stress," Amanda Mummert, an anthropology graduate student at Emory University, said in a news release.

Compounding the problem, growth in population density spurred by agricultural settlements led to an increase in unsanitary conditions ripe for spreading infectious diseases and the transmission of novel viruses from livestock to humans, she added.

Eventually, this trend reversed itself and average heights for most populations began to increase. This is most evident in the 75 years or so since the industrialization of agriculture in the developed world.

The finding is based on a review of skeletal data on populations from various corners of the world, including China, Southeast Asia, and North and South America. Mummert and colleagues looked at skeletal height as well as dental cavities, bone density, and other indicators of health.

"Culturally, we’re agricultural chauvinists. We tend to think that producing food is always beneficial, but the picture is much more complex than that," Emory anthropologist George Armelagos, co-author of the review, said in the statement.

The findings support a theory he proposed in the 1984 book, "Paleopathology at the Origins of Agriculture," which showed a decline in health and rising nutritional diseases as humans shifted from foraging to agriculture. 

So, if the transition to agriculture was bad for our health, why did we do it? 

The geneticist Spencer Wells argues in his 2010 book, "Pandora's Seed: The Unforeseen Cost of Civilization,"  that the transition was driven by a cold snap between 12,700 and 11,500 years ago called the Younger Dryas. 

In the Near East, the cold spell was also a dry spell, which was bad news for hunter-gatherers there who had settled some of the world's first villages and subsisted on easily foraged fields of wheat and barley. 

The arid climate meant the grains clung to moist niches in the hills, not the valleys where the hunter-gatherers settled. The commute to the hills to forage grains was unsustainable. So someone — most likely a woman since they did most of the gathering — Wells argues, had the brilliant idea to plant grains closer to home. 

"Her first efforts must have been rewarded with admiration from the entire village," he writes. "Virtually overnight, humans had gone from being controlled by their food supply to controlling it." 

More on agriculture, health, and evolution:

John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).