You might know about sticky rice. It’s pretty popular in Asian cuisines, often used in desserts and specialty dishes. It’s sometimes called “glutinous rice”, but it doesn’t actually contain gluten. Instead, it’s sticky because of the chemistry of its starch. Sticky rice starch is almost 100% made of the gluey carbohydrate amylopectin, while the regular rice starch is a mix of amylopectin and amylose.
Rice isn’t the only grain with a sticky variety. One of the others is sticky corn, or “waxy corn”. Waxy corn has the same kind of starch as sticky rice, rich in amylopectin and lacking amylose. Like sticky rice, it’s also popular in Asia – you can buy it at Korean grocery stores in the US.
In fact, waxy corn has been popular all over Asia for centuries, a fact which made several western botanists in the mid-20th century very confused indeed. If corn is from the Americas, why is waxy corn only grown in Asia, and why has it been there so long?
Korean waxy corn
Zongzi, a dish made with sticky rice
The puzzle
The facts were pretty straightforward:
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Columbus’s crew found corn (maize) fields growing abundantly in the Bahamas and Cuba on their 1492 voyage, so clearly maize was there before he was.
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In Asia, maize was reported less than a century later – by Spanish Jesuit Antoni de Montserrat in 1581.1 Before then, there aren’t many European accounts of Asian crops.
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By the time western botanists were finding waxy maize in particular at the beginning of the 20th century, that variety was already cultivated in places across Asia – from Shanghai to Burma to the Philippines – but in isolated pockets mainly in rural backwaters, not across the entire region.
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Waxy maize wasn’t cultivated anywhere outside of Asia before the 1900s.
This left a few possibilities:
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Waxy maize was developed independently in different parts of Asia after 1492, and somehow was never developed in America.
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One waxy breed was developed in Asia after 1492 and spread across Asia, but somehow never became popular or was abandoned, except in these isolated rural areas.
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Waxy maize was developed in the Americas and somehow Europeans never found it.
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Maize came to Asia before 1492, leaving more time for Asians to develop new varieties, and somehow never showed up in Polynesia or Siberia along the way, or left archaeological evidence.
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Maize is actually originally an Asian crop and made it to the Americas before 1492, and somehow all the previous evidence of maize being American was wrong.
The controversy
Guy N. Collins
Guy N. Collins, who first brought waxy corn to the attention of western scientists in 1909, originally thought it was evidence that Maize came to Asia before Columbus sailed.2 By the time of a 1920 paper describing waxy corn kernels from Upper Burma,3 Collins had been considering that waxy corn was brought over from the Americas, but a thorough survey of American corn varieties came up empty. Once the new kernels were found in Burma, he abandoned that hypothesis.
By 1923, other scholars’ work had convinced Collins that corn had been brought to Asia after 1492, and waxy corn developed there.4 And in 1924, scientists in Connecticut found some waxy kernels on two ears of flint corn from a local farmer, suggesting that waxiness could arise from a simple mutation or recessive gene.5
Assam (yellow) in India
That wasn’t the end of it, though. In 1949, Charles Robert Stonor and Edgar Anderson were studying corn varieties grown in the hills of Assam in Northeastern India, including waxy varieties – which the locals said had been grown there since before anyone could remember. Stonor and Anderson concluded that there were in fact two separate races of maize in Asia, one pre-Columbian and one post-Columbian,6 and that possibly maize was originally Asian.
But there was immediate pushback, and in 1951 Paul C. Mangelsdorf and Douglas L. Oliver published a rebuttal,7 in no uncertain terms:
“Basically, however, the lines are drawn between those who are short on facts and use them uncritically (although sometimes with superb imagination) and those who demand evidence and valid reasoning.”
Harsh, but fair. Mangelsdorf and Oliver systematically tore apart each of Stonor and Anderson’s points of evidence and provided so much independent evidence of their own, that it’s hard not to accuse Stonor and Anderson of motivated reasoning. In 1909, perhaps, it was a fair conclusion, but not in 1949.
Modern perspective
Today, waxy corn is grown across the world, and its gooey starch is used as a thickener for packaged foods.8 Modern scholars now generally agree that maize came to Asia after Columbus, spreading from the Spanish and Portuguese to India via Arab trade routes, and then from India to China and elsewhere in Asia. We think waxy corn came from a single origin somewhere in Asia, and farmers used to sticky rice cultivated it intentionally. It was probably grown in isolated pockets because that’s where it grew better than rice.
That said, there are other crops that could have spread across the Pacific before Columbus. The best candidate is sweet potatoes, which are also native to the Americas but seem to have been grown on several Polynesian islands centuries before 1492. So even if waxy corn may not be the best evidence for transpacific contact, the overall story may still have a kernel of truth.
Coming soon: Mbabaram for dog is “dog”.
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