Ancient Egypt used local cotton crops

DNA analysis of 1,600-year-old cotton has cleared up the mystery of where ancient Egyptians’ cotton was domesticated. Archaeologists were unsure whether ancient Egyptians had imported domesticated cotton from the Indian subcontinent, as had happened with other crops, or whether they were growing a native African variety that had been domesticated locally. Using the latest generation of DNA sequencing technology, a new study led by the University of Warwick confirms that seeds taken from a site in Egypt’s Upper Nile were of the G. herbaceum, variety, native to Africa, rather than G. arboreum, which is native to the Indian subcontinent. The site, Qasr Ibrim, is located about 40 kilometers from Abu Simbel and 70 kilometers from the modern Sudanese border on the east bank of what is now Lake Nasser. This is a site that was occupied for more than 3,000 years by five successive cultures—Napatan, Roman, Meroitic, Christian, and Islamic. The seeds found there were remarkably well preserved given their age, and contained virtually no bacteria thanks to the extremely dry conditions at the site. Robin Allaby, from the School of Life Sciences, says the findings confirm there was an indigenous domestication of cotton in Africa, separate from the domestication of cotton in India. “The presence of cotton textiles on Egyptian and Nubian sites has been well-documented but there has always been uncertainty among archaeologists as to the origin of these. “It’s not possible to identify some cotton varieties just by looking at them, so we were asked to delve into the DNA. “We identified the African variety—G. herbaceum, which suggest that domesticated cotton was not a cultural import—it was a technology that had grown up independently in Africa.” As well as the archaeological evidence, the use of cotton in Egypt and along the Nile Valley has been documented by classical authors. Cotton was said to have been cultivated in Nubia (modern-day northern Sudan) by Pliny in the 1st Century AD and by Pollux in the 2nd Century AD. The same study, published in the journal Molecular Biology and Evolution, also found what scientists believe is the first evidence of punctuated evolution—long periods of evolutionary stability interspersed by bursts of rapid change—having occurred in a major crop group. The results showed that even over the relatively short timescale of a millennia and a half, the Egyptian cotton, identified as G. herbaceum, showed evidence of significant genomic reorganization when the ancient and the modern variety were compared. The study also looked at South American cotton samples from sites in Peru and Brazil aged between 800 and nearly 4,000 years old. The South American cotton, of the closely related G. Barbadense variety, showed genomic stability between the two samples, even though these were separated by more than 2,000 miles in distance and 3,000 years in time. This divergent picture points towards punctuated evolution having occurred in the cotton family.