March 2, 2014

Useful bottle gourd likely floated here from Africa in ancient times

Simulations confirmed that a bottle gourd traveling from West Africa could make it to North or South America in nine months, on average.

By the time Columbus arrived in the New World in 1492, bottle gourds had already conquered much of the globe. After evolving in Africa, one species, Lagenaria siceraria, made a break for East Asia around 11,000 years ago and eventually took up residence in Polynesia, China, Peru and beyond, earning the title of most widely distributed pre-Columbian domesticated plant.

When dried, the gourds have been supremely useful as containers, medical and musical instruments, even decorative birdhouses. Despite their ubiquity, though, they have their secrets. Archaeological evidence shows that ancient peoples living in Florida and Mexico began using them at least 10,000 years ago. Yet how they got to the Americas remained unknown. Until now, maybe.

In 2005, scientists 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. Also, 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, reports a new study in Proceedings of the National Academy of Sciences: The founding bottle gourds did not come from Asia after all but instead traveled to the Americas directly from Africa.

Researchers isolated DNA from modern bottle gourds around the world and ancient ones found in 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 America or South America in nine months, on average.

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