Happy National Watermelon Day!! It's one of my favorites... it's both considered a fruit and vegetable. I'm going to say fruit, because it's sweet.
Recently, there's been a bit of a stand-off in the scientific world about correctly identifying and classifying the fruit. According to one melon researcher, the Latin name given to the sweet fruit centuries ago—Citrullus lanatus—is wrong. In Latin, the word "lanatus" means woolly or hairy. It's more likely that the name refers to the misidentified, sometimes-furry citrus melon. For years scientists believed that the wild variety of watermelon simply evolved into what we eat at picnics today, but new evidence suggests that modern-day watermelons are an entirely new species that evolved from western varietals. In fact, there are still wild watermelons in south & central Africa that are much closer genetically (as well as in taste and appearance) to the original watermelon. In fact, only recently have that scientists and historians figured out the exact origins of the watermelon.
The word "watermelon" actually refers to many different species of fruit (or vegetable depending on your source), many of which are a result of selective breeding. The so-called original watermelon was likely what we now refer to as the "wild watermelon." Indigenous to Africa, archaeological remains (mostly seeds) dating back about five millenia have been found in parts of Libya. However, these large round fruits were much different from watermelons today. The inside of this ancient wild variety was the exact opposite of the modern-day fruit. It was hard, pale and immensely bitter. A century later, seeds and images of watermelons began popping up in Egyptian tombs. But these Egyptian paintings showed a fruit that was oblong - similar to the shape of many modern watermelons and not round, as researchers believe the original wild fruit was.
As a watermelon expert explained to National Geographic in 2015, the Egyptians valued the watermelon not for its taste but for its namesake. In a desert climate like Egypt, there were few things more valuable than water. A food that is 92 percent water is a tremendous resource. In addition, watermelons, unlike most fruit, can remain edible for weeks if uncut and stored in a cool, dry area. While practical and filled with water, the watermelons of the past were still unpleasant to eat.
We know humans began experimenting with selective breeding and improving crop varieties as long as 6,000 years ago. Within this time, it appears that the ancient Egyptians began the process of breeding out the undesirable traits of watermelon—like the bitter taste and hard texture. They weren't the only ones. As trade between civilizations became more common, the fruit spread across the globe and each group of people began to cultivate their own watermelon patches that matched the desired traits they wanted in the fruit.
Watermelons can be found described in ancient texts, from Greek to Hebrew. They are often described as cool, wet, and sweet. By the third century, writings often grouped watermelons with other desert fruits like figs, grapes and pomegranates.
Besides taste, other traits changed as well. The shape changed from round to oblong. More prominently, the inside hue of the fruit went from a pale color to bright red. The sugar content of the watermelon is tied to the presence of a certain gene that also affects the pigmentation of sucrose. In other words, the sweeter it is, the redder it is. However, this particular change didn't happen overnight, or even in a century. Images that date to the 1st century CE still show the interior in a yellowish-red hue. It wasn't until the 1400s that the watermelon's color matched what today's melons.
Watermelon was a favorite of Mark Twain, who once remarked that "When one has tasted (watermelon), he knows what the angels eat." While humans have consumed the fruit for 5,000 years, it took centuries of selective breeding with certain varieties and genetic traits to produce the sweet, red fruit we eat today.