National Museum of Natural History, Washington DC, and Smithsonian Tropical Research Institute, Balboa, Republic of Panama

An archaeologist tells how her research interest sheds light on the history of her favourite fruit.

My mother gave me a lot of sage advice during my childhood. This sometimes countered prevailing wisdom, such as her recommendation that I should eat bananas, not apples, every day.

The nutritional qualities of bananas were underappreciated when I was growing up in Philadelphia, Pennsylvania, although their value as a crop had been recognized millennia before.

A recent paper (B. Lejju et al. J. Archaeol. Sci. 33, 102–113; 2006) reports that bananas were being cultivated in Africa as long as 5,000 years ago.

The investigators reached this conclusion by studying phytoliths — highly durable pieces of silica that form in plant cells — that had been dug up in Uganda. I use phytoliths (and starch grains) in my own research into the history of agriculture, so it was more than just my fondness for bananas that drew me to this paper.

Phytoliths tell us which crops grew where and when, and so in turn can teach us about human cultures. Part of what makes this finding interesting is that bananas aren't native to the African continent. Wild bananas grow in eastern Asia, Australia and Melanesia. Hence the Ugandan bananas represent ancient human transport, probably through trade across the Indian Ocean with societies that were already growing the plant.

The age of the banana phytoliths also rivals presently available dates for the domestication of important, indigenous plants such as sorghum. However, I suspect that when phytolith and starch-grain analysis is applied to the history of native African crops, the date of their domestication will be pushed further back.