The breadfruit trail: the wild ancestors of a staple food illuminate human migrations in the Pacific islands

Natural History, Dec, 2003 by Nyree J.C. Zerega

Many years ago a god named Ku came to Hawai's and married a mortal woman. Together they had a large family but Ku never told her he was a god. One year, a terrible famine came to the islands, and Ku's family became weak with hunger. When Ku could no longer bear his family's suffering, he confided to his wife: "If I go on a long journey, I can get food for our children and everyone on the island, but I will never beable to return." At first his wife would hot hear of-such a thing, but after watching her children slowly starve, she finally relented. The couple walked together into their garden, where Ku kissed his wife good-bye and disappeared into the earth. In her grief Ku's wife waited at the spot where he had disappeared, watering it for several days with her tears. Soon a sprout pushed up from the spot and rapidly grew into a tree. Within just a few days Ku's body had transformed into a large tree trunk, his arms into branches, his blood into a white latex flowing through the tree, and his head into a fruit that provided Ku's family with the food he had promised. The tree, and the food, was the breadfruit.

This legend is just one of many that are told to account for the origins of breadfruit (Artocarpus altilis). It is little wonder that the plant is the stuff of legend, for it has been cultivated as a staple starch crop in the Pacific islands for thousands of years. Biologists, however, are still looking for a more down-to-earth explanation of the plant's origins. The puzzle begins with the fact that many breadfruit trees are seedless and sterile. Sometime in the past, cultivators must have transformed a fertile plant into one that needs human intervention to reproduce itself. But what was the ancestral tree? Breadfruit is scattered across thousands of islands in the Pacific, but no close wild relatives grow throughout much of this range. Thus there is no prime local candidate for botanists to name as breadfruit's ancestor. And if the transformation did not occur throughout the Pacific, it probably occurred in just one place, and the sterile trees must have been spread by human means. But where did these people come from?

Seafaring people reached Australia and New Guinea at least 40,000 years ago and, relaunching from those lands, settled the Solomon Islands by 30,000 years ago. But the broader peopling of Oceania--the middle and southern Pacific islands--did not get underway until about 4,000 years ago. Most scholars attribute the resurgence in settlement to a people they call the Lapita, after an archaeological site in New Caledonia. The main evidence for the patterns of their migrations comes from tracing a characteristic style of pottery in which geometric and, occasionally, representational designs were stamped into the clay. Linguistic and genetic data generally support the archaeological conclusions.

The Lapita, thought to have come from somewhere in island Southeast Asia, first traveled to the northern coast of New Guinea. They continued their migrations eastward through Melanesia and into the far reaches of eastern Polynesia, making their way to Easter Island by about 1,700 years ago [see map on pages 48 and 49]. Micronesia is much more culturally and linguistically heterogeneous than Polynesia, and its island groups were probably settled by migrants who came at various times from island Southeast Asia, Melanesia, New Guinea, and elsewhere. The last of the principal Oceanic islands to be settled were the Hawaiian Islands, about 1,700 years ago, and New Zealand, about 1,200 years ago--in both cases by Polynesians.

Prehistoric seafarers casting off from their home islands to settle elsewhere would have been sure to take along breadfruit trees, which provide an abundance of fruit. The first breadfruit trees, like their unknown progenitor, may have been capable of reproducing by means of seeds. At some point, however, the voyagers must have begun to transport and transplant root cuttings, which can be nicked with a sharp blade to produce shoots. In that way the trees were propagated vegetatively throughout Oceania.

If migrating people were responsible for the propagation of breadfruit, finding its wild progenitor might contribute to far more than the botanical problem of finding the origins of the plant. By tracing the paths of ancient breadfruit, light might be shed on the routes taken by the ancient mariners who transported it. Unfortunately, reconstructing the plant's botanical history has long proved difficult. During the millennia breadfruit has been cultivated, the trees changed with time and place. Mutations occurred, and cultivators on various islands selected for trees that grew best under local particularly conditions or whose fruits were particularly appealing in size, taste, and texture. My hope was that DNA evidence obtained through the new tools of molecular biology would finally resolve the puzzle of the species' origins.

Scholars have put forward at least two testable hypotheses about the origins of breadfruit. The first was advanced in 1940, when Eduardo Quisumbing, a Filipino botanist, suggested bread-fruit may be "derived, by selection, from some species perhaps even approximating the 'camansi.'" He was referring to the breadnut, A. camasi, native to New Guinea and possibly the Philippines and the Moluccas. It produces edible, chestnut like seeds. A second, much more complex hypothesis was proposed in 1960 by Francis Raymond Fosberg, an accomplished American botanist of the Pacific flora. Fosberg implicated two other species in addition to the breadnut. One is the Philippine endemic commonly known as antipolo (A. blancoi), which is used primarily for lumber. The other, often called dug-dug (A. mariannensis), is endemic to certain uplifted limestone islands in Micronesia, namely Palau and the Marianas. The islanders consume both its seeds and the surrounding flesh.