February 12, 2010 Leave a comment
The taming of the turkey
It’s not unusual for our domesticated familiars to have gone through several cycles of domestication. In the Old World, pigs and sheep and cows submitted to the process several times. But the New World has only a few examples of its own homegrown domesticates, and now, thanks to some fossilized poop, we can trace the taming of the turkey.
Mitochondria and coprolites
Using coprolites–that’s the poop–and mitochondrial DNA, researchers describe in a study published in PNAS having nailed down the domestication of the turkey in the American Southwest. The previous idea was that the turkey was like beans, maize, and squash–it made its domesticated way to the Southwest by way of trade routes from southern Mexico. Indeed, in southern Mexico, indigenous peoples had domesticated their own version of the bird.
But the southwesterners had their own version, too, and mitochondrial DNA–which passes from mother to offspring and accumulates mutations at a slow, predictable rate–shows that their turkeys came from a different species.
Modern turkeys are imports
You might think that the turkeys around today came from one or the other of these turkey lines, so carefully bred 2000 years ago. Nope. Europeans showed up, took some turkeys back to Europe. There, other Europeans produced some deeply inbred turkeys that then made their way via import back to the Americas. The turkeys we eat today, the ones that make the centerpiece around a Thanksgiving table or in a Sarah Palin interview, may trace back to southern Mexico, but they’re now really inbred European imports. Good thing Ben Franklin didn’t get his way when he allegedly proposed the turkey as the national bird for his fledgling nation.
Ideas for questions
Why do you think mitochondrial DNA accumulates mutations more slowly than, say, nuclear DNA?
Explain why mitochondrial DNA passes only from mother to offspring.
How do you think the researchers could tell whether or not turkeys were inbred?
Coprolites are trace fossils, while fossilized bones are body fossils. What are other examples of trace fossils? What can these trace fossils tell us in the absence of body fossil information?