Jack-o-lanterns, butternut squash soup, pumpkin pie — autumn wouldn’t be complete without squashes and gourds. Squashes originated in the Americas before the arrival of humans and became dietary and cultural staples for the first residents of Mesoamerica around 10,000 years ago.
But our modern favorites, like zucchinis and Jack-o-lantern pumpkins, looked — and tasted — a lot different back then, said Logan Kistler, curator of archaeobotany at the Smithsonian’s National Museum of Natural History. “Wild squashes are bitter and toxic, and have thin rinds,” he said. As humans planted, used and ate squashes and gourds over time, they ushered along the evolution of these species into the fruits we cook and display today.
Unearthing past plants
Archaeobotanists, like Kistler, excavate and examine preserved plant remains to untangle how humans used them — and how humans changed them. Very seldom do archaeologists come across mineralized plant remains in which the soft tissue of seeds or fruits harden over time into inorganic minerals, Kistler explained. More common, he said, are carbonized remains that are preserved by being burnt. Plant material loses its organic matter but can retain its physical shape during burning, and researchers often glean insights about past diets from charred material left in the remnants of a cooking fire.
Plants can also be preserved by desiccation in caves or rock shelters, where super-dry conditions prevent plant tissues from breaking down. “That’s really great for preserving gourds and squashes because it preserves all the minute details, and we can extract DNA from those,” Kistler said. The inverse process, waterlogging, can also yield valuable results. “At the bottom of a bog, things can preserve for tens of thousands of years,” he said, because such environments are oxygen-starved and inhospitable to microbes that would otherwise aid in the plant materials’ decomposition.
Kistler’s scientific collaborators have even found evidence of prehistoric gourds in fossilized dung, yielding clues not just about what plants existed in the past, but also how they changed over time. “We have 30,000-year-old mastodon dung deposits from Florida that have well-preserved squash seeds in them,” he said. Research Kistler conducted along with National Museum of Natural History archaeologist Bruce D. Smith revealed that giant mammals like the mastodon ate wild squash and scattered its seeds in new corners of North America before humans stepped in and started using them.
Bottle it up
Some of the first known plants used by humans were bottle gourds, durable hard-shelled fruits that are often hourglass-shaped. Bottle gourds, also known as calabashes, appear in the archaeological record around 11,000 years ago in Asia, Kistler explained. But they also show up in the Americas around the same time and in Africa just a bit later.
How did bottle gourds make that continental leap? It’s possible they were carried around the globe by migrating humans, or maybe they drifted across the ocean then landed and grew on distant shores. In 2014, Kistler and Smith found that New World bottle gourds are most closely related to those of West Africa, and that the currents and wave patterns of the Atlantic Ocean could have carried viable seeds tucked in the fruits’ watertight shells in just about nine months.
Across locations, humans used the gourds’ hollowed-out shells as receptacles and containers. “They’re interesting because they’re not used for food — they’re tools,” Kistler said of the gourds.
Early humans soon began growing their own calabashes, likely selecting for thicker and tougher flesh. People today still use the plants as bottles or cups, but also as the bodies of instruments, to create puppets, in food and even “for fishnet floats, or to float rafts down rivers,” Kistler said.
Bottle gourds belong to the same taxonomic family as inedible ornamental gourds and cooking favorites like butternut and summer squash. The main difference between gourds and squashes is that gourds are grown to be used or displayed, while squashes are grown to be eaten.
Squashes belong to the genus Cucurbita and are all native to the Americas, originating in Mexico around 10,000 years ago. They soon became dietary and cultural staples for the early humans of Mesoamerica who cultivated and altered them through the process of domestication.
Domestication is “a really fuzzy process,” Kistler said. “It’s not something that has a clear, definite beginning. And it’s certainly not something that has a definite end, because evolution doesn’t finish.” But at some point in squash history, the plants changed physiologically and genetically such that they were more suited to growing in human-made situations than in the wild, he explained.
Evidence of squash domestication predates that of maize by around 1,000 years, but the two crops became inextricable dietary essentials along with legumes, which were introduced later. Indigenous North Americans from the Maya to the Iroquois planted squashes, corn and beans together in a technique known as the “Three Sisters.” Each crop contributed a benefit to the others: the beans wind up the cornstalks like a trellis, microbes affixed to the bean roots help capture useable nitrogen in the soil and the squash plant’s wide leaves shade the entire operation. Together the three crops provided a robust array of nutrients.
What’s in the can?
Chances are your Thanksgiving dinner will feature a heavily domesticated squash: the flavorful and creamy fruit that goes into the canned pumpkin. “That’s called the Dickinson field pumpkin,” Kistler said. This pumpkin doesn’t resemble the bright orange spherical fruits we love to carve and display, but rather “it’s more related to a butternut squash,” he said. It’s a highly cultivated variety, and has been refined for taste.
American farmer Elijah Dickinson developed this varietal on his fields in the 19th century, and later bought a cannery with his brothers in central Illinois. They sold the facility to the Libby family in 1930, and cans with the Libby’s brand name containing Dickinson’s namesake pumpkin sit on grocery store shelves today.