For most families, Thanksgiving dinner would be unthinkable without turkey on the table. Long before the arrival of European settlers, wild turkeys populated the United States, Mexico and Central America and the Aztecs were busily domesticating them. The conquistadores took some of these domesticated birds back to Spain, and before long Europeans were breeding them into a much plumper version. Interestingly enough, European settlers brought some of these domesticated birds back to the New World in the 1600s and eventually began crossing them with America's wild turkeys. Most U.S. turkeys raised today are from the White Holland variety, which has been bred to produce a maximum of white meat (a U.S. favorite). In fact, the breasts of today's turkeys are so massive that they must rely on artificial insemination because they can't get close enough to mate. Although male (tom ) turkeys can reach 70 pounds, those over 20 pounds are becoming less and less available. The female (hen ) turkey usually weighs from 8 to 16 pounds. Gaining in popularity is a smaller version of both sexes (sometimes called a fryer-roaster ), which weighs in at between 5 and 8 pounds. The trend toward these compact turkeys is the result of both smaller families and the desire of turkey producers to make turkey everyday rather than exclusively holiday fare. Turkeys are available fresh and frozen year-round. They're sold both whole and as separate parts — such as breasts or drumsticks. Some whole turkeys have had a built-in plastic thermometer implanted that pops up when the turkey is done. Self-basting turkeys have been injected with butter or vegetable oil. Smoked turkey — whole or breast — is also available, as is canned boned turkey. Turkey is very similar to chicken in many regards, including USDA grading.