On this day of Halloween, when ghoulish jack-o’-lanterns decorate our homes and public spaces, it may be interesting to reflect on the fact that pumpkins – and indeed all squashes – came very near to going extinct… and that human beings probably saved them.
Big Fruits for Big Animals
Squashes and pumpkins belong to the genus Cucurbita, a genus restricted to the New World. In their wild form, they form creeping or climbing vines that bear baseball-sized fruit.
Recent findings show that, up to about 14,000 years ago, squash fruits were eaten by the American megafauna: mastodons, giant ground sloths, gomphotheres (an extinct family of elephantlike animals), etc. We know this because their seeds are found in the fossilized dung of these animals. By eating the fruit without digesting the seeds, the megafauna ensured that wild squash seed was spread far and wide and thus ensured the survival of the many different species that existed at the time.
Wild squash fruits have a very hard shell and are very rich in cucurbitacins, highly bitter compounds that are even toxic if ingested in quantity. Smaller animals would have had a hard time opening the fruits and an even harder time digesting them. Even today, sheep are occasionally killed by eating wild squash.
Interestingly, modern elephants seem indifferent to the bitterness and toxicity of cucurbitacins and readily consume and easily digest fruits rich in cucurbitacins. Presumably this was also the case with the megafauna of the time. Scientists believe that cucurbitacin levels evolved specifically to be palatable to the largest megafauna species while discouraging smaller animals from eating them.
So, thanks to their large size, their hard shell and the bitter compounds they contained, squash could only be distributed by megafauna.
When the Seed Distributor Disappears…
But the New World’s megafauna disappeared about 11,000 to 14,000 years ago, a period that corresponds with the arrival of human beings in the New World, and many specialists blame their disparition on humans who apparently hunted them to extinction. But even if they disappeared for some other reason, the result is the same: all New World mammals larger than a bison disappeared. And without their “seed distributors”, squash too began to decline.
Most squash species became extinct at that time, although a few species are still found in the wild in areas where there is less competition. Even the species that gave our modern pumpkins and zucchinis, Cucurbita pepo, no longer exists in the wild.
But then about 10,000 years ago, squash remains start showing up in the sites occupied by humans. The domestication of squash had begun!
At first they were only used for their hard outer shell: indeed, when emptied out, they could readily serve as containers; when cut into slices, they became tools. And humans could also eat very immature squash, as cucurbitacins only build up over time.
Gradually, however, selections with fewer cucurbitacins were developed and soon the direction of squash domestication took on a whole new turn. Varieties were now chosen not for a hard outer rind, but thick, sweet, tasty flesh with as little bitterness as possible. Seeds too of these new squash were edible. This led to the development of the hundreds of squash varieties Native Americans already grew prior to the arrival of the first Europeans… and the hundreds more developed since, given that squash are now grown around the world.
Saved From Extinction!
And so it is that humans, after having first put squash on the path to extinction by eliminating their megafauna seed distributors, eventually came to develop a symbiotic relationship with them and saved them from extinction!
Knowing that, you may never look at a jack-o’-lantern the same way again!
You’ll find more information about megafauna squash distribution here.
This text was originally published on this blog October 31st 2016.