The watermelon, according to Australian chemist James Kennedy, may just possibly be the most unnatural fruit in the world. What Kennedy means is that the watermelon, in the hands of humans, has been changed so significantly that it’s now nothing like the original fruit.
Fans of the British sci-fi comedy Red Dwarf may remember the ship’s cat, who evolved over three million years into a narcissistic humanoid with an obsession with fashion. You’d never take it for a cat. And frankly, that’s pretty much the same with the watermelon.
The ancestral watermelon was native to Africa, and it was a bitter little fruit about two inches in diameter.
Today, due to countless creative generations of breeders, the watermelon averages over two feet in diameter—a 1,680-fold increase in volume over its many-times-great-grandparent—and weighs in somewhere between four and 18 pounds, though modern growers also routinely produce Brobdingnagian whoppers. According to the Guinness World Records, the world’s heaviest watermelon as of 2013, from the garden of Chris Kent of Sevierville, Tennessee, weighed a tad over 350 pounds. That is the size of a bear. The puny ancestral watermelon, in contrast, weighed about three ounces.
Unlike its little predecessor, the more accessible modern watermelon is easily sliced (or smashed) open, revealing its sweet, red flesh. Red flesh is a relative latecomer in the watermelon’s long history of artificial selection. Just consider the famous still life by Italian artist Giovanni Stanchi, for example, probably completed in the mid-1600s. Scholars debate exactly what it’s showing, but the watermelon here is distinctly weird-looking, with a lot of whitish flesh heavily packed with whorls of seeds.
Its flesh—actually the watermelon’s placenta, the tissue that surrounds the seeds—lacked the modern fruit’s hefty concentration of lycopene, that bright-red carotenoid pigment that puts the color in today’s watermelons, tomatoes, and red grapefruit. The watermelon today, in fact, is top of the lycopene list, containing 40 percent more of it, ounce for ounce, than the tomato. Health-wise, this is a plus since lycopene is a powerful antioxidant. Studies suggest that diets high in lycopene lower the risk of heart disease, certain cancers, and age-related eye disorders. In other words, when it comes to watermelon, feel free to dig in.
The watermelon became more unnatural yet in the 20th century with the introduction of the seedless watermelon, which now comprises the bulk of the watermelon market.. Watermelons are rendered seedless by colchicine, a chemical derived from crocuses, which causes the watermelon chromosome number to double. Back-crossing a doubled (tetraploid, four sets of chromosomes) watermelon with a normal (diploid, two sets of chromosomes) watermelon produces the watermelon version of a mule – a triploid (three sets of chromosomes) seedless fruit that produces, at best, thin white slivers of immature protoseeds.
The numbers show that we love the easily munchable, seedless watermelons – but some researchers point out that chucking the seeds may not be in our best interests. In fact, some nutritionists argue, we should eat them. Sprouted watermelon seeds—which taste pretty much like sunflower seeds—are packed with protein, vitamin B, magnesium, and good fats, of the sort that have been shown to reduce cholesterol levels and cardiovascular disease. But does the flesh taste less sweet than the black-seeded variety? That’s a matter for debate.
The modern watermelon is undeniably pretty unnatural—though as unnatural goes, it’s got competition. Kennedy the chemist cites sweet corn, which went from an inch-long, tooth-cracking cluster of kernels on its ancestral teosinte to the foot-long, mouth-wateringly sweet corn-on-the-cob of today.