Noni, Morinda citrifolia, is in the family Rubiaceae, which includes such notables as Coffee, Gardenia, and Cinchona, the quinine tree. It is one of perhaps 80 species in the genus Morinda, spread worldwide through the tropics. Many of these species have origins in the area that includes Borneo, New Guinea, Northern Australia, and New Caledonia: it is out of this population that Morinda citrifolia is thought to have evolved and spread.

Plants have several ways to travel between land masses separated by large amounts of ocean. Before the intervention of humans, these were, mainly, by water, either floating on the ocean currents or hitchhiking on something else like a log or other such flotsam, and by air, carried by hurricane or bird or bat.

Noni is a very salt-tolerant tree that thrives in wet or dry conditions. There is a membrane enclosing a gel-like substance around each seed enabling flotation, and the seed coating, being very hard and watertight, can delay sprouting for many months. The flower is self-pollinating, so only one seed needs to sprout for a successful population to possibly emerge. These are positive traits for sea or air dispersion and colonization in any harsh conditions, from salt flats to lava flows.
The Polynesian People are perhaps the principal method of spreading Noni throughout its known range, now from Africa to India and Southern China all through the South Pacific to Central and South America. They were some of the finest sailors from the beginnings of time, with ingenious craft that rivaled the speediest of today, and they explored and settled all through the Pacific and related oceans, even as far as to be the closest genetic relatives of the Eskimos. The Polynesians carried with them essential plants to sustain them in unknown situations; Noni was one of these, chosen for its medicinal value and perhaps its use as a famine food as well; they certainly brought it as far as Hawaii, where it coexists with a native species, Morinda trimera, in lowland forests.

Noni is eaten and used as medicine by the Australian Aborigines, a people who have lived in the same place for perhaps 40,000 years. Morinda is mentioned in the chants of the Rig-Veda from ancient India, one of the first writings ever, transcribed from oral traditions and thought to be as old as 14,000 years.