In spite of the wide variety of shapes and sizes, all hard-shelled gourds are members of the same species, Lagenaria siceraria (also synonymous with L. vulgaris and L. leucantha). They belong to the family of plants known collectively as Cucurbits; as the name suggests, this is the same family to which belong cucumbers, as well as all squash, pumpkins/ melons, luffas, and ornamental gourds.
The origin of cultivated Lagenarias remains something of a mystery; they are unquestionably one of the earliest cultigens, and it is quite interesting that the nature of early agriculture focused not on food production, but utility (Flannery, 1986). With truly wild relatives occurring only in Africa, bottle gourds (as they are often called) do not occur as convincing "wild" populations elsewhere in their domestic range. Although inconclusive, Africa provides the most probable genesis for the domesticated gourd.
In any event, gourds had not only arrived in the New World by the Archaic, but had spread by cultivation into Peru and as far north as central Mexico by 7000 BC (Flannery, 1986). By the time they had reached these areas (and probably long before), their use as net floats had presumably been augmented by other, more obvious functions such as water bottles and eating utensils. In the southeastern United States, Lagenarias can be comfortably dated to at least 1000 BC (Hudson, 1976). With the less problematic introduction of gourds into Asia by overland transportation, they became a mainstay of traditional life throughout the temperate and tropical world for thousands of years.
Research of anthropologists and biologists suggests that the domesticated bottle gourds widely used by prehistoric peoples were likely brought to the Americas some 10,000 years ago from Asia. Since bottle gourds are thought to have originated in Africa, the previously held theory was that the gourds had floated across the Atlantic ocean from Africa and were picked up and used as containers once they reached the Americas. Genetic comparisons showed that the gourds found at archaelogical sites in the Americas were a closer genetic match to modern-day gourds in Asia. The current research suggests that these bottle gourds may have been brought in boats from Asia, hand-carried across a land bridge, or floated across the Bering Strait.
The gourds of northeastern Asia were originally transported by humans from their native Africa. When humans harvest, store, and plant seeds over a sustained period, the plant populations adapt through genetic and morphological changes making it possible to distinguish the populations from the various regions. In addition to providing information about the origin of American gourds, it is interesting to note that this research shows that the bottle gourd -- essentially a container, not a food crop -- is the earliest known domesticted plant grown here. Radiocarbon dating indicates that gourds were used as containers in the New World for at least 9000 years.
(The collaborative research was done by scientists from Harvard University, the Smithsonian Institution's National Museum of Natural History, Massey University in New Zealand and the University of Maine. The full report is available online on the website of the Proceedings of the National Academy of Sciences.) Go to: http://www.pnas.org/cgi/content/full/102/51/18315
Radiocarbon dating indicates that bottle gourds were present in the Americas by 10,000 years ago and widespread by 8,000 years ago. Some of the specimens studied were not only the oldest bottle gourds ever found but also quite possibly the oldest plant DNA ever analyzed.
The Bottle gourd or calabash gourd has been reported to be the only cultigen most widely dispersed and common both to the Old World and New World since ancient historic times.
Archaeological reports on the occurrence of this pantropical species were recorded from several regions of the world, viz., Ocampo cave, Tamaulipas (7000 BC), Coxcatlan cave, Tehucan valley (5000 BC), sites near Ancon, Peru (2700 BC), Njora river cave, East Africa (1000 BC), a fifth dynasty Egyptian tomb (2500 BC), Spirit cave, Thailand (7000 BC), and China (2000 BC) (Leakey and Leakey, 1950; Cutler and Whitaker, 1967; Chang, 1968; Gorman, 1969; Pickersgill, 1969; Harlan, 1975). According to Decker-Walters et al. (2001), molecular analysis suggested the dispersal of bottle gourd fruits from Africa to Asia and the Americas during pre-Columbian times was followed by independent domestication on all three continents.
Previously, researchers speculated that the gourds floated here from Africa, although they had no way to prove it. In 2005, a team of scientists challenged that notion. They analyzed short fragments of DNA taken from living and archaeological bottle gourds and found that ancient North American specimens shared more in common with Asian than with African gourds, so perhaps the colonizers who crossed the Bering land bridge more than 10,000 years ago took gourd seeds with them.
But that did not explain how the bottle gourd, a plant that prefers tropical climates, could have survived such harsh winters. Moreover, ancient American seeds more closely resemble the fatter, oddly shaped African seeds than the thinner, more symmetrical Asian ones.
Now, it seems, those questions have finally been answered. The founding bottle gourds did not come from Asia after all, but instead traveled to the Americas directly from Africa, a new study in Proceedings of the National Academy of Sciences reports.
To arrive at this conclusion, researchers used a relatively new method of genetic analysis called high-throughput sequencing. “The technology has come an incredibly long way since the 2005 study, so now we can look at this question in a lot more detail,” said the lead author, Logan Kistler, a postdoctoral fellow in anthropological genomics at Penn State.
To recreate the plant’s family tree, the researchers isolated DNA taken from modern bottle gourds around the world and ancient ones found at nine archaeological sites throughout the Americas. The pre-Columbian artifacts from the New World, they found, were linked directly to African relatives. This means the gourds floated to the Americas on their own.
To double-check this conclusion, the team created a computer model of Atlantic Ocean currents. Simulations confirmed that a bottle gourd traveling from West Africa could make it to North or South America in nine months, on average. Once there, given the right conditions, the seeds could very likely take root. (A 1954 study found that bottle gourds could spend up to a year floating in saltwater without losing fertility.) The diversity of New World gourd populations suggests that there were several successful oceanic crossings throughout history.
Some mysteries remain, however. Scientists are not sure how the gourds managed to spread from New World shores across entire continents, or why wild bottle gourds no longer grow in the Americas. Dr. Kistler and his colleagues hypothesize that large animals might have spread the gourds’ seeds, and when those animals later went extinct, the wild bottle gourds did the same.
Changing climate could also have played a role. “The study is another step forward, but we are still far from understanding what really happened,” said Hanno Schäfer, a botanist at the Technical University of Munich who was not involved in the work. Further detailed studies “will probably be the only way to really answer the question without the need of storytelling,” he said.
Analyzing bottle gourds from archaeological sites elsewhere in the world could help fill in those details, as could examining genetic material found in the cells’ nuclei.
“At this point, I think we can say we’re confident that bottle gourds did travel from Africa, but that certainly isn’t the end of the story for the species,” Dr. Kistler said. “There’s always more to learn.”