Science Supersized Thanksgiving Dinner

Your corn is sweeter, your potatoes are starchier and your turkey is much, much bigger than the foods that sat on your grandparents' Thanksgiving dinner table.

Most everything on your plate has undergone tremendous genetic change under the intense selective pressures of industrial farming. Pilgrims and American Indians ate foods called corn and turkey, but the actual organisms they consumed didn't look or taste much at all like our modern variants do.

In fact, just about every crop and animal that humans eat has experienced some consequential change in its DNA, but human expectations have changed right along with them. Thus, even though corn might be sweeter now, modern people don't necessarily savor it any more than their ancestors did.

"Americans eat a pound of sugar every two-and-a-half days. The average amount of sugar consumed by an Englishman in the 1700s was about a pound a year," said food historian Kathleen Curtin of Plimoth Plantation, a historical site that recreates the 17th-century colony. "If you haven't had a candy bar, your taste buds aren't jaded, and your apple tastes sweet."

The traditional Thanksgiving dinner reflects the enormous amount of change that foods and the food systems that produce them have undergone, particularly over the last 50 years. Nearly all varieties of crops have experienced large genetic changes as big agriculture companies hacked their DNA to provide greater hardiness and greater yields. The average pig, turkey, cow and chicken have gotten larger at an astounding rate, and they grow with unprecedented speed. A modern turkey can mature to a given weight at twice the pace of its predecessors.

In comparison with old-school agriculture or single-gene genetic modification, these changes border on breathtaking. Imagine your children reaching full maturity at 10 years old.

This human-directed evolution has generated animals and plants that share little more than a name with their wild or pre-industrial farm-domesticated relatives. The accumulation of agricultural breeding knowledge and consumer testing has resulted in plants and animals that are physically shaped by consumer tastes. Americans like a medium-size corn kernel, so kernels aren't too big or small. American consumers like white meat, so turkeys are grown with larger breasts.

The breeding programs of the last half-century are, in some ways, a tremendous scientific accomplishment. For example, the United States pumped out 33 times more pounds of turkey at a lower cost to consumers in 2007 than our farmers did in 1929.

Turkeys more than doubled in size in that time from an average of 13 pounds to an average of 29 pounds, and as seen in the chart above, show no signs of stopping. If the trend continues, we could see an average turkey size of 40 pounds by 2020. According to the National Wildlife Turkey Federation, the largest wild turkey on record is 38 pounds.

In fact, in commercial and academic turkey-breeding programs, adult male turkeys, called toms, can reach 50 pounds at the tender age of five months, said John Anderson, a longtime turkey breeder at Ohio State University. "We get 50 pounders at 20 weeks, but that's at the top edge of our normal distribution," Anderson said. "We've got some adult male-line birds that went over 80 pounds."

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