Thanksgiving week promises many things, foremost among these delights are the physiology lessons offered by turkey carving.

The bird is presented to the world belly upward, as if in a dissecting dish. The carving knife scalpel slides through the skin, crossing feather tracts still visible as goose (really?) bumps, and cleaves a slice of pectoralis muscle. Who wants light meat? Then, after more blade-work, the femurs are dissociated from the pelvic girdle. Dark meat for anyone?

So many questions on one serving platter. Why the difference in color and taste? Are all birds this way? If we were to throttle then roast that insufferable Thanksgiving guest, would we have the same choice of meat cuts for our plates?

Turkeys are walkers. They fly only in short, plosive bursts. A startled turkey is a trebuchet of feathers. It twangs from the forest floor before smashing into the trees’ ramparts. The projectile moves fast — as much a forty miles per hour, I’m told — but has no staying power. Such bursts of power are delivered by “fast-twitch” muscle fibers that excel in anaerobic bursts, but then sag into exhaustion. Such muscles need relatively little oxygen and so their meat, when cooked, has none of the stain of blood or blood vessels.

Muscles in the legs are aerobic. They squeeze and pump all day without tiring. Such continual low-intensity activity requires “slow twitch” muscle fibers that are amply supplied with blood, capillaries, mitochondria, and oxygen-holding myoglobin. Under the knife: dark meat.

Turkeys are avian curiosities, though. Most other bird species use their wings for sustained flight and their legs for occasional strutting. In these species, therefore, the locations of dark and light meat are the reverse of the turkeys’ arrangement. A chickadee Thanksgiving would be instructive, although the meal would be short. From the roastlings’ chests we could carve slices of dark flight muscle, from the legs, the whiter meat.

As the breeders of industrial monstrosities know, most Americans prefer light meat to dark. By picking out the birds with the thickest and widest chest muscles, poultry scientists have bred varieties that by conforming to the desires of shoppers have lost the ability to grow to full adulthood without leg, lung, and wing problems. A pardoned turkey is not necessarily a lucky turkey.

And for that special Thanksgiving guest, the one whose boorishness or political rants add a spice of loathing to the table, remember that humans, too, have fast and slow twitch muscle fibers. Mostly, our muscles comprise a mix of the two, but the lower back and calf muscles are like turkey legs, always in use and so very dark. When the conversation reaches its nadir, such knowledge can provide a self-protective glaze of therapeutic imaginings.