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Captain Cook and the Impossible Cotton

by Brian Dunning

November 18, 2014

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Donate Shortly before Captain James Cook was killed on the island of Hawaii in 1779, one of his botanists, David Nelson, made a single four-day excursion up Mauna Loa and collected 136 species of plants. From Reader's Digest's 1986 book, Mysteries of the Ancient Americas:
When Captain Cook landed in 1778, Hawaiian cotton—a wild hybrid species with one set of chromosomes from New World cotton and another from Old World cotton—was already well established. How did it get to be a hybrid, and how did it get to Hawaii? ... If Old World people and New World people each brought their respective cotton plants to Hawaii, and the hybridization occurred there, where are the two parent species?
This struck me as a true puzzle, and more importantly, one with far-reaching implications. Such a plant might well overturn much of what we've learned about the prehistoric colonization of the Americas and the Pacific islands. Our studies have taught us that no genetic link exists between the original populations of these two regions, but proof that such a crop existed could throw a serious monkey wrench into that knowledge.

The first step was to examine Nelson's records, and right away it became clear that no cotton was among the plants he described and/or brought back to England. However, a steady stream of Europeans flowed into the Hawaiian Islands following Cook, and cotton is thoroughly described in their many newer botanical reports. Which was the mysterious hybrid?

Sea Island Cotton (Gossypium barbadense) is the species most often described. Today it's what we commonly call Egyptian Cotton, but despite its name, it is native to Peru. The early botanists report that it was introduced to Hawaii around 1816, so it is not the elusive native hybrid. In fact, the early botanists wrote very little about the mystery species.

Today we know it as Hawaiian Cotton (G. tomentosum), and it is the only species native to the islands (but was not found on the island of Hawaii itself, perhaps explaining its absence from Nelson's report). To the Hawaiians, the plant was called ma'o, and they ground its leaves into a green dye and its flowers into yellow dye. Its red-brown cotton fibers were sometimes plucked and used for pillow stuffing that they called hulu hulu ("hairy hairy"). Ma'o is quite different from other cotton species around the world, although newer genetic studies have proved that it is closely related to American Upland Cotton (G. hisutum), native to Mexico and Central America, and the most common industrial species that you're probably wearing right now. It's virtually certain that ma'o seeds came to the islands from America—either floating, carried in bird feces, or on debris—from a species ancestral to both G. hirsutum and G. tomentosum.

So... What about its seemingly impossible status as an unexplained New World/Old World hybrid? Well, apparently, the mystery stands explained simply by the fact that this is not the case. To be sure, botanists and geneticists have studied its ancestry just as much as they have other plants, and come to some preliminary findings along the way. In 1956, it was noted that G. tomentosum had characteristics of both G. hirsutum and G. barbadense (both New World species). In 1975, researchers studying its leaves guessed that it was closest to G. mustelinum (native to Brazil). In 1979, studies of its pigments pegged it as most similar to G. barbadense and G. darwinii (native to the Galapagos, also in the New World). But nowhere in the literature did I find a case where anyone had concluded that G. tomentosum appeared to be a hybrid between any of the New World cottons and either of the Old World cottons (G. arboreum from India, and G. herbaceum from Arabia).

The mystery is not how this apparently "impossible" cotton came to be, but rather how the Reader's Digest authors came to the conclusion that such a fanciful hybrid was ever on Hawaii at all. And thus we are able to enjoy another example of one of our favorite pastimes here at Skeptoid Media: eliminating the popularly promoted "mystery" consisting purely of pseudoscience or pseudohistory, and replacing it instead with a real-life mystery still to be solved by someone with deeper document-diving skills than me.

Thanks to Bruno van de Casteele for his help with this.

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Dejoode, D., Wendel, J. "Genetic Diversity and Origin of the Hawaiian Islands Cotton, Gossypium Tomentosum." American Journal of Botany 79 (11): 1311-1319 (1992)

Nagata, K. "Early Plant Introductions in Hawaii." The Hawaiian Journal of History, vol. 19: 35-61 (1985)

St. John, H. "The Vegetation of Hawaii as Seen on Captain Cook's Voyage in 1779." Pacific Science 33 (1): 79-83 (1979)

by Brian Dunning

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