A Natural History of Thanksgiving Dinner

The Thanksgiving dinner menu is often pretty standard. When you’re feeding a large group of people with picky kids (and adults) to satisfy, and traditions to uphold, it doesn’t pay to get crazy. You can’t go wrong with  turkey, green beans, potatoes, cranberry sauce, and pumpkin. But have you ever thought about what those foods are like before they get to your table? You may have given thanks for the bounty, and perhaps even for the Earth that provided them. But do you think about how and where they’ve grown in the dirt, under the hot sun, for thousands of years? Or  the odd adaptations that keep them alive? Maybe  your “normal” Thanksgiving dinner is pretty extraordinary.

Let’s start at the end, with pumpkin pie. If you’re ambitious, you may have  baked a pumpkin and scooped the soft, orange flesh out of the rind. Although I enjoy pumpkin pie, I’ve often thought it a little weird to take a vegetable, mix it with sugar and eggs, and make a dessert. Personally, I prefer a berry pie.

But, to  a botanist, a pumpkin is a berry! Scientifically speaking, a berry is a fleshy fruit produced from a single flower. Pumpkins are a  type of thick-walled berry known as a pepo. Appropriately, the scientific name for the pumpkin is Cucurbita pepo. C. pepo is also the name for the acorn squash, delicata squash, spaghetti squash, pattypan squash, zucchini, and ornamental gourds. Despite the fact that some on the list are hard-skinned winter squash, and some are soft and juicy summer squash, they are all fruits of the same species of plant.

That plant was domesticated from its wild ancestors about 10,000 years ago. We know this from the large seeds—characteristic of C. pepo, but not it wild cousins—that were unearthed in a cave in Oaxaca, Mexico, and dated using carbon-14. That makes pumpkins and their cousins the oldest known domesticated plants in the Americas.

While the beans in your green bean casserole aren’t quite that old, they are one of the longest-cultivated plants in the Americas. Kidney, black, pinto, and navy beans all were domesticated in South America. As with pumpkins, many types of beans all belong to the same species: Phaseolus vulgaris (vulgaris means common). Green beans are simply the unripe fruit of various cultivars of the common bean -- selected especially for the fleshiness, flavor, or sweetness of their pods.

Long before humans domesticated beans, the beans developed their own beneficial relationship with another organism. Through a series of chemical signals, soil bacteria called rhizobia trigger the bean plant to grow deformed root hairs that expand into nodules. The bacteria waltz on in, becoming guests in the bean plant’s spare room. While the bean feeds the rhizobia with carbohydrates, proteins, and even oxygen, rhizobia are not moochers. The bacteria possess the rare talent of taking nitrogen out of the air, and fixing it into a form that the beans can use.

This special relationship between the beans and the bacteria impacts our relationship with beans, too. Nitrogen is a basic building block of amino acids, and amino acids are the basic building blocks for protein. The mutualistic symbiosis that beans have with rhizobia give the beans the high protein content we desire.

The bean plants themselves also make pretty good houseguests. Microscopic hairs on their leaves can be used to trap bedbugs!

Leaves from the potato plant are also bad for bugs. All parts of the potato plant – except for the tuber itself – contain toxic alkaloids like solanine that are supposed to protect the plant from its predators.

Human predators–hunters--are one of the biggest causes of mortality for the Thanksgiving centerpiece. Hunters are responsible for two thirds of the mortality in tom turkeys. Of course, you probably weren’t eating a wild turkey. But if you were, could you have figured out how good his genes were, and if he had intestinal parasites or not? The hens could have!

Turns out, it’s all in the snood. This fleshy outgrowth hangs down over the male’s beak and is used to dissipate heat when he’s strutting his stuff. A longer snood also signals to the ladies that he has good genes that are helping him ward off intestinal parasites. What a life!

All of the dishes on our Thanksgiving table were made from living things. But before they went into the pot, they had lives filled with history, drama, stress, and relationships not so unlike ours. And now, their lives are part of ours, sustaining us with vital products created in their very own bodies. “How calmly, as though it were an ordinary thing, we eat the blessed earth.” -- Mary Oliver.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! The current exhibit, “Nature’s Superheroes—Adventures with Adaptations,” opens in May 2014 and will remain open until March 2015.

Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.