The estimated 45 million turkeys that many Americans eat on Thanksgiving are genetically distinct from their wild turkey ancestors.
"Ancient turkeys weren't your Butterball," Rob Fleischer, head of the Smithsonian Conservation Biology Institute's Center for Conservation and Evolutionary Genetics, said in a press release. "We set out to compare the genetic diversity of the domestic turkeys we eat today with that of the ancestral wild turkey from South Mexico. Some of what we found surprised us."
He and his colleagues determined that the domestic turkey that ends up on the dinner table has less genetic variation than not only its ancestral wild counterparts, which were first domesticated in 800 B.C., but also than other livestock breeds, such as domestic pigs or chickens.
The genetic traits affected by the variation are body size and breast muscle development - features that can help determine the likelihood of a consumer buying a turkey.
"Few people know that the commercial turkeys served at Thanksgiving descended from Mexico, where they were discovered during the Spanish Conquest and transported to Europe," said Julie Long, senior author of the study and research physiologist with USDA's Agricultural Research Service in Beltsville, Md.
"During the next 100 years, Europeans created many different varieties of the domesticated turkey. It's important to assess the differences between ancient and modern domesticated turkeys in the event that some unforeseen problem might threaten the stability of the commercial turkey lines."
The scientists sequenced the genomes of domestic turkeys from seven commercial lines and compared them to those of three South Mexican turkeys collected in 1899 from Chihuahua, Mexico. The ancient turkey samples came from specimens at the Smithsonian's National Museum of Natural History.
"It is often the case that selection in domestication reduces the level of variation," Fleischer said. "What did surprise us, however, is how well the ancient DNA from the three museum specimens worked to generate the genome sequences needed to determine the genetic variation and structure. These data and this approach show great promise for determining what genes were involved in the process of turkey domestication."
The findings were published in BMC Genomics.
As a side note, turkeys in the 19th century were often boiled instead of roasted for fancy dinners. I'm guessing that the meat from these birds was tougher, but perhaps more flavorful. Isabella Beeton, the Martha Stewart of her day, wrote about the "noble dish" of turkey in 1859. Some companies still sell free-range "wild" turkeys.