Waterlogged seeds reveal melons’ ancient journey
DNA in seeds recovered from Chinese port help trace origins of symbolic fruit
Washington University in St. Louis
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A waterlogged melon seed remain uncovered from Shuomen Gugang
view moreCredit: Photo: Xinyi Liu and Melissa Ritchey
By Talia Ogliore
Melons produce many seeds, making the melon shape a traditional symbol of fertility and prosperity in Chinese culture. But the historical debate about how melons made their way to modern tables is as long and twisted as the vines they grow on.
A new study published in Proceedings of the National Academy of Sciences reveals newly discovered aspects of melons’ ancient history. Based on an analysis of the ancient DNA of seeds from a Song imperial dynasty archaeological site in southeastern China (circa 960-1279), scientists at Washington University in St. Louis have determined those ancient melons in East Asia likely arrived from South Asia, rather than being developed from wild Chinese plants, and that they lacked the sweetness of modern dessert melons.
These melons’ flesh color likely resonated with Song dynasty aesthetic sensibilities, as seen in jade-green celadon ceramics that were locally crafted in melon-shaped forms.
Taken together, the study offers a rare and compelling example of how cultural tastes and crop traits may have influenced each other, the researchers said. The study is also an example of how scientists can use ancient DNA to answer historical questions beyond what macro-botanical evidence or artifacts alone can reveal.
Biologist Susanne Renner, in WashU Arts & Sciences and co-author of the new PNAS study, has studied melons for more than 25 years. “At that time, it was assumed that because the genus Cucumis, to which melons belong, has numerous wild African species, that melons originated in Africa,” she said.
But Renner was never convinced. In 2010, she published a study based on some 100 Cucumis samples from Africa, Australia and Asia that showed that melon has numerous previously overlooked species-level relatives in Australia and around the Indian Ocean. “Based on biogeographic analysis, we inferred that melons most likely originated in Asia, not Africa,” Renner said. It is now clear that melon domestication has occurred independently once in Northeast Africa and twice in India, but archaeobotanical evidence points to a possible additional domestication event in southeastern China.
Renner worked with colleagues in Germany and the United Kingdom on the analysis that the melons came from South Asia, rather than locally domesticated despite older archaeological evidence in the region, warranting further investigation. There are two paths they might have taken, the researchers said: a northern “Silk Road” along the foothills of the Inner Asian Mountains and the northern margin of the Tibetan Plateau, or a southern “Tea Horse Road” along the southern slopes of the Himalayas and through the valleys of southwest China.
“Both corridors are historically plausible, as demonstrated by the movement of other food resources,” Liu said. “Current archaeological evidence points more strongly to a southern route. The earliest melon remains in China have been recovered from Han and pre-Han royal tombs in southern China, predating comparable finds from northern ‘Silk Road’ sites by approximately 800 to 1,000 years. We therefore consider a southern route connecting southern China with Southeast and South Asia to be a candidate for the early introduction of melon into China.”
Their genomic analysis also revealed other intriguing facts about the kinds of melons grown in China in the 10th to 13th centuries.
“The color-related traits are particularly interesting. They suggest that these ancient melons likely had light-green flesh and yellow peel,” Liu said. “Melons with these characteristics are often consumed as vegetables, as mildly sweet fruit, or for their seeds, rather than as high-sugar dessert melons. In the lower Yangtze region today, culinary traditions of consuming melon as pickles or vegetables still persist.”
Liu and Renner said that even today, there are only a handful of crops for which ancient DNA has been obtained and placed in context with the evolution of specific traits. These include the economically important crops of barley, certain types of wheat, cotton, maize and beans. “The difficulty lies in the generally very few substitutions that can be attributed to selection on specific traits,” Renner said.
The melon’s flesh color itself may have held cultural and symbolic significance during the Song Dynasty, Liu said.
“The light-green color resonates with the fine-toned color of Chinese jade and with the glazes of celadon porcelain, both highly valued in East Asian aesthetic traditions,” he said. “During the Song dynasty, green celadon ceramics produced in the lower Yangtze region and beyond were frequently fashioned in melon-shaped forms, with glazes echoing the jade-green tones of melon flesh.”
Such greenware ceramics was popular across East Asia, including China, Korea and Japan, and many examples were recovered from Gugang, Liu said. It might have been popular across the region due to the melon’s symbolic value of fertility and abundance.
“Taken together, this represents a rare and compelling case of cultural-genetic symbiosis, reflected in the parallel historical selection of melon traits and celadon aesthetics,” Liu said.
Which is why Renner was intrigued when she sat down next to WashU colleague Xinyi Liu, a professor of archaeology in Arts & Sciences, at a WashU Living Earth Collaborative event. Liu told her about many archaeological seeds, including those that were recently uncovered in an excavation of a medieval port in southeastern China.
Located in present-day Wenzhou, the Gugang port (Shuomen Gugang) helped connect continental East Asia with the Pacific and Indian Ocean worlds during the Song dynasty. An archaeological excavation of the port in 2024 uncovered sunken shipwrecks with large quantities of porcelain and imported fruits such as grape, olive, lychee, kiwifruit — and melons.
Amid this submerged world, Liu saw opportunity. Ancient genetic research relies on exceptionally favorable preservation conditions, where plant DNA are likely to survive. The waterlogged deposits at Gugang represented one such location.
Post-excavation image of Shuomen Gugang, the southeastern China port where WashU archaeologists uncovered ancient melon seeds.
Credit
Photo: Yufei Zhen
