Short answers, pulled from the story.
The sweet potato is the first known naturally transgenic food crop, carrying DNA sequences from the bacterium Agrobacterium within its own genome. This genetic anomaly was actively expressed by the plant for millennia before scientists discovered it. No other major food crop possesses this natural genetic modification without human intervention.
The sweet potato originated in the tropical regions of South America, specifically in what is now Ecuador, where it was domesticated between 5,000 and 8,000 years ago. The oldest radiocarbon-dated remains of the crop were discovered in caves within the Chilca Canyon in south-central Peru, dating back to 8080 ± 170 BC. This places the sweet potato's history deep in the pre-Columbian era, long before the arrival of Europeans.
Sweet potatoes were already being grown in Polynesia before the arrival of Europeans, generally spread by vine cuttings rather than by seeds. Radiocarbon dating of sweet potatoes in the Cook Islands places their presence there between 1210 and 1400 CE, suggesting a pre-Columbian contact between Polynesians and South Americans. Genetic and linguistic evidence supports the idea that Polynesians traveled to South America and back, bringing vine cuttings with them to central Polynesia.
The sweet potato was introduced to the Fujian province of China in about 1594 from Luzon in response to a major crop failure. In Japan, sweet potatoes were introduced in the early 1600s by the Portuguese to the Ryukyu Kingdom, present-day Okinawa, and became a staple because they were crucial in preventing famine when rice harvests were poor. The Shōgun Tokugawa Yoshimune even planted sweet potatoes in his private garden, recognizing their value as a reliable food source during times of scarcity.
Sweet potato cultivars with dark orange flesh have more beta-carotene, which is converted to a higher vitamin A content once digested, making them a critical tool in combating vitamin A deficiency in Africa. In a 100-gram reference amount, baked sweet potato provides 100% of the Daily Value for vitamin A and 24% for vitamin C. The plant's nutritional profile includes 76% water, 21% carbohydrates, 2% protein, and negligible fat, with rich contents of vitamin A, vitamin C, manganese, and vitamin B6.
In 2020, global production of sweet potatoes was 89 million tonnes, led by China with 55% of the world total, followed by Malawi, Tanzania, and Nigeria. It is the fifth most important food crop in developing countries, and studies are being done to develop a salt-tolerant variety to combat the effects of climate change. The plant's ability to grow in poor soils with little fertilizer makes it an ideal crop for developing nations, and studies show it is the most efficient staple food to grow in terms of farmland, yielding approximately 10,000 calories per hectare daily.