The Origin of Bananas

[Source: Anne Vézina]

'Where our bananas come from' (1962) was published in the 'New Scientist magazine'. In it, Norman Simmonds wrote that to answer the question on where cultivated varieties of banana come from, “we must go back to Malaysia several thousand years ago, for it was there that men took the first decisive steps in converting the inedible, wild, seedy bananas of the jungles into the lush, parthenocarpic and sterile fruit that we know today”.
Nobody denies that Southeast Asia is a centre of domestication of banana. It’s just that Simmonds should have known better, if only because a few years earlier he had been in a collecting mission to Southeast Asia and the Pacific. During that trip, he visited what is now Papua New Guinea, where he observed a diversity of bananas he had not seen anywhere else. The unusual thing about these edible bananas is that like their wild ancestors they have two sets of chromosomes (diploids)[1], as opposed to the three sets of chromosomes (triploids) found in most cultivated bananas. Because in Asia edible diploids had been largely displaced by the more productive triploids they had given rise to, Simmonds assumed that the diploids he saw in Papua New Guinea had been introduced from Southeast Asia early in the domestication process and had owed their survival to the late arrival of triploid bananas. Except for the unusual Fei bananas – which Simmonds recognized as having been domesticated in the Pacific because their wild ancestor(s) are not found elsewhere – he could not imagine that bananas tracing their origin to Musa acuminata alone, or hybridized with Musa balbisiana, had been domesticated outside Asia.

Subsequent genetic analyses and the discovery of 7,000-year-old banana phytoliths[2] at Kuk Swamp in the highlands of Papua New Guinea, now a UNESCO World Heritage Site, proved Simmonds wrong. New Guinea and nearby islands, including the Solomon Islands, are definitely centres of domestication of banana.

Analysing the genetic make-up of hundreds of banana cultivars revealed that more than one subspecies of Musa acuminata have been implicated in the domestication of bananas. Since these subspecies occupy distinct geographic regions, different subspecies at various stages of domestication must have been moved around in order to come into contact and hybridize. It means that the meeting of Malaysian and New Guinean bananas, among others, was facilitated by people sharing genetic resources.

Starting 2,000 to 4,000 of years ago, the ancestors of Plantains and East African highland bananas went west to Africa, where they continued to diversify, making Africa a secondary centre of diversity. In the other direction, many of the New Guinean bananas were taken east by seafarers, eventually landing in Hawaii. And maybe South America, but that’s another story.

[1] Humans also have two sets of chromosomes, one inherited from the mother and the the other from the father
[2] Phytoliths are microscopic stones made of silica that form in plant cells and are used as archaeological markers for plants that, like domesticated bananas, do not produce seeds and pollen. To see what they look like, See here.

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