martes, febrero 09, 2010

Turkeys: So Good People Tamed Them Twice

By Sujata Gupta
ScienceNOW Daily News
2 February 2010

Americans love turkeys, so it's surprising how little researchers know about the birds' early relationship to humans. Many archaeologists credited Mesoamericans--who lived in the area extending from present-day Mexico to Honduras--with bringing domesticated turkeys to North America sometime between 200 B.C.E. and 500 C.E., much like they brought maize, beans, and squash. But a new study shows that Native Americans in what is now the southwestern United States likely tamed turkeys on their own.

Double domestication. Residents of the southwestern United States might have independently tamed turkeys like the one shown on this ancient bowl from New Mexico.
Credit: Courtesy of the Amerind Foundation Inc.

The history of the turkey, one of the few animals to be domesticated in the New World, has proven elusive. In part, that's because the turkey is so well-traveled. The Spaniards, for instance, took the bird from Mesoamerica to Europe in the early 16th century and then brought it back to the Americas 100 years later as a food source. (Descendents of these returnees are believed to be the turkeys present in most grocery stores today.) And the National Wild Turkey Federation initiated a trap-and-release program in the 1950s that moved subspecies of wild turkeys all over the country. In the meantime, wars, settlement, and disease wiped out most wild turkey populations.

Brian Kemp, a molecular anthropologist at Washington State University, Pullman, and colleagues tested the DNA from almost 200 bones and coprolites--the scientific name for very old, dry poop--from 38 archaeological sites in the American Southwest dating from 200 B.C.E. to 1800 C.E. (Coprolites retain ancient DNA particularly well, Kemp says. "Smell these turkey droppings after they've been rehydrated, and it smells like you're on a farm," he says.) The group also analyzed genetic samples from 10 Mesoamerican wild turkeys--now extinct, but preserved at the Smithsonian Institution--12 samples from turkeys bought in U.S. grocery stores, and almost 300 turkey sequences already in the GenBank database. They homed in on 12 tightly linked genes on a single chromosome, known as haplotypes, across the various turkey breeds.

They found that the southwestern turkeys were very distantly related to Mesoamerican wild turkeys. Apparently, the Native Americans who lived in that part of the Southwest, known as the Puebloan Ancestors, didn't inherit domesticated turkeys from the Mesoamericans, but took care of domestication themselves, the team reports online in the Proceedings of the National Academy of Sciences. It's not unusual for the same species to be domesticated multiple times, Kemp notes. For instance, pigs were tamed in Africa, the Near East, and Asia.

Surprisingly, the Puebloans didn't domesticate wild birds native to the Southwest. Rather, southwestern turkeys share haplotypes with modern-day wild turkeys found in the Midwest and along the Eastern seaboard. The researchers speculate that the Puebloans may have traveled east to catch these birds for their superior feathers. Turkey feather blankets replace rabbit fur blankets at about the same time turkey remains begin to appear in archaeological sites, says Kemp's Washington State colleague William Lipe.

There are so many connections between southwestern and Mexican prehistoric cultures, but very few extending from the Southwest to the east, says Kathy Roler Durand, an archaeologist at Eastern New Mexico University, Portales. "Who would have thought this was possible? she says. "I would have bet money against [it]."

Evidence that the domestic turkey in the Southwest might have originated farther east validates an idea proposed in 1980 by ethnozoologist Charmion McKusick of the former Southwest Bird Laboratory in Globe, Arizona. Lacking genetic testing technology, McKusick, now 79, relied on skeletal characteristics of ancient turkeys, such as muscle imprints left on bone. "I measured 7000 turkeys," she says with some indignation. "So of course I'm not surprised."

"We could not replicate [McKusick's] measurement studies ... so we weren't persuaded" at the time, says Robin Lyle, a turkey researcher with the Crow Canyon Archaeological Center in Cortez, Colorado. But now "it's all beginning to make sense."

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