The 5,000-year secret history of the watermelon

~ By Mark Strauss, National Geographic 
Folllow Mark Strauss on Twitter.

Ancient Hebrew texts and Egyptian tomb paintings reveal the origins of our favorite summertime fruit.

The watermelon has long inspired artists, such as Giuseppe Recco's Still Life With Fruit (1634-1695). The first color sketches of the red-fleshed, sweet watermelon in Europe can be found in a medieval medical manuscript, the Tacuinum Sanitatis.

 
PHOTOGRAPH BY DEA, A. DAGLI ORTI/DEAGOSTINI/ GETTY

To taste a watermelon is to know "what the angels eat," Mark Twain proclaimed.

The angels, however, would have gagged if they had eaten the watermelon's wild ancestor - a bitter fruit with hard, pale-green flesh. Generations of selective breeding, spanning several countries and cultures, produced the sweet red fruit that's now a common sight on picnic tables.

Much of this epic history has been lost to antiquity. But Harry Paris, a horticulturalist at the Agricultural Research Organization in Israel, has spent years assembling clues – including ancient Hebrew texts, artifacts in Egyptian tombs and medieval illustrations - that have enabled him to chronicle the watermelon's astonishing 5,000-year transformation.

Who's your Daddy?

Scientists agree that the watermelon's progenitor - the ur-watermelon, if you will - was cultivated in Africa before spreading north into Mediterranean countries and, later, to other parts of Europe.

But, that's where the consensus ends. Did the ancestral watermelon originally grow in Western Africa? Southern Africa? Northeastern Africa? The theories are, literally, all over the map.

"The history has been screwed up from the very outset," says Paris, who places the blame on generations of taxonomists, stretching back to the 18th century, who hopelessly muddled melon classification.

Even the name for the modern watermelon - Citrullus lanatus - is wrong. Lanatus means "hairy" in Latin and was originally the name applied to the fuzz-covered citron melon (Cirtrullus amarus).

The citron melon, which grows in southern Africa, is one popular candidate for the watermelon's ancient ancestor. But Paris is doubtful. He's found evidence that the Egyptians began growing watermelon crops around 4,000 years ago, which predates farming in southern Africa.

Contestant number two is the egusi melon from western Africa. Again, Paris is skeptical. Egusis weren't cultivated for their flesh, but for their edible seeds - the one part of the modern watermelon that nobody wants.

Paris says the true ancestor of the modern watermelon is indigenous to northeastern Africa: citrullus lanatus var. colocynthoides, known as gurum in Sudan and gurma in Egypt.

"Why go all the way to western Africa, to a country like Nigeria, when you have these watermelons still growing wild in the deserts of Egypt and Sudan to this very day?" says Paris.

Pharaonic Fruit

People have been eating watermelons for millennia. We know this because archaeologists found watermelon seeds, along with the remnants of other fruits, at a 5,000-year-old settlement in Libya.

Seeds, as well as paintings of watermelons, also have been discovered in Egyptian tombs built more than 4,000 years ago, including King Tut's. One tomb painting, in particular, stands out. The watermelon depicted in the image is not round like the wild fruit. Instead, it has the now-familiar oblong shape, suggesting that it was a cultivated variety.

A fair question to ask is why the Egyptians began cultivating wild watermelons in the first place. The fruit was hard and unappetising, tasting either bitter or bland. Yet somebody at some point said, "Hey, let's grow more of these!"

The answer, according to Paris, is in the fruit's name: water. Unlike other fruits, watermelons could remain edible for weeks or even months if kept in a cool, shaded area. A National Geographic correspondent visiting Sudan in 1924 saw watermelons being collected and stored this way during the dry season, when they would be periodically pummeled to extract their water.

Paris believes the Egyptians were drawn to the fruit for the same reason. And, he adds, it's why we find remnants of watermelons in tombs, "These Egyptian pharaohs, when they died they had a long journey ahead of them so they needed a source of water – and what would that source of water be?" says Paris.

Once the Egyptians began cultivating watermelons, Paris suspects the first trait they sought to change was the taste. Just one dominant gene was responsible for the bitter flavor, so it would have been relatively easy to breed it out of the population.

After that, watermelon growers began selectively breeding for other traits. In that respect, the tomb painting of the oblong melon, which is shown resting on top of a food platter, reveals a clue to how the melon was changing. Since it was being served fresh, it must have been tender enough to cut and eat. Gone was the hard flesh and the need to pound it into watery pulp.

But while the fruit was no longer hard and bitter, it had not yet fulfilled its destiny as the sweet, tender watermelon that we enjoy today.

Hitting the Road

After 2000 B.C., the watermelon's historical trail must be teased out of medical books, travelogs, recipes and religious texts. By studying and comparing descriptions from several sources, Paris was able to deduce the ancient names for the watermelon and track its many uses.

Writings from 400 B.C. to 500 A.D. indicate the watermelon spread from northeastern Africa to Mediterranean countries. Paris speculates that, in addition to trade and bartering, the watermelon's territorial expansion was aided by its unique role as a natural canteen for fresh water on long voyages.

The ancient Greek name for the watermelon was the pepon. Physicians, including Hippocrates and Dioscorides, praised its many healing properties. It was prescribed as a diuretic and as a way to treat children with heatstroke by placing the cool, wet rind on their heads.

The Roman naturalist, Pliny the Elder, was also a fan, describing the pepo as a refrigerant maxime - an extremely cooling food - in his 1st-century encyclopedia, "Historia Naturalis."

Paris confirmed that the ancient Hebrew name for watermelons was avattihim. He found a trove of clues in three codices of Jewish Law that were compiled millennia ago in Israel: the "Mishnah," "Tosefta" and the "Jerusalem Talmud."

The most exciting reveal in the Hebrew writings was a tract, written around 200 A.D., which placed the tithed watermelons in the same category as figs, grapes and pomegranates.

And what do all of those fruits have in common? They're sweet. By the 3rd century, the watermelon had graduated from desert crop to dessert. And if sweet watermelons were in Israel, they had likely spread across the Mediterranean.

Taste the Rainbow

Descriptions from that era describe ripe watermelons as having a yellowish interior. Likewise, a Byzantine-era mosaic in Israel, from around 425 A.D., depicts what appears to be a cut watermelon with yellow-orange flesh.

In subsequent years, the watermelon would take on its familiar red hue. That's because the gene for the color red is paired with the gene that determines the sugar content. As watermelons were bred to become even sweeter, their interior gradually changed color.