Plants which are now important to man in one part of the world in some cases have traveled 1000 of miles from where they were first domesticated. This has partly arisen due to demographic differences around the world and sometimes climate changes over the millennia in some cases favour areas where these crops grow now rather than where they used to grow. It has often been possible to track back where plants were domesticated by looking at natural diversity, archaeological remains, comparing genetic finger prints of wild plants with domestic plants to find similarities. In addition linguistic similarities have been used to determine who moved crop species around the world, this is particularly useful in plants that moved around in Pre history. In Maize for example there are a series of secondary centres of evolution which have been linked to the development of different cob shapes and forms these are closely linked to human migration, settlement and agricultural intensification in different areas.
How did they travel?
Crops that moved around the World before 1492
Some crops may prove that man was capable of intercontinental trade well before Columbus sailed across the ocean blue. Based on linguistic and other pieces of information it has been suggested that plantains reached the tropical rainforests of West Africa by sea from Western South East Asia by 3000 years ago. Certainly banana suckers can withstand long periods of being carried around semi drying before being replanted The origins of the main species used for cotton production are much debated. Gossypium hirsutum comes from the North of South America and Central America. But genetic information indicates that one of the parental lines in its lineage is only found in Africa, if it reached America did this parent die out? Was this a result of a hybridisation before the continents split up, or due to sea washing up seeds of the African species on the shores of South America? Or more intriguingly was it a result of early human travel?
One proven example of intercontinental movement in pre Colombian days is sweet potato. This species definitely originated in South America but analysis of preserved tubers found in Lord Howe Island showed that the movement predated the time of Columbus.
Crops that moved around the World after 1492
The main production centres for sweet potatoes are not linked to either of these locations but are a result of movement by Spanish and Portuguese explorers. The Spanish and particularly the Portuguese were responsible for a lot of movement of crops between the “new” and the “old” world.
The movers and the stickers
In some cases such as rice the centre of origin in China is still tallies today with one of the largest areas of production. Similarly Mexico is still important for maize production but lags behind other areas. By contrast Soya, lettuce, sugar cane and sweet potato do not feature as major crops in their original centres of origin but feature strongly economically in other areas of the same continent or other continents. Lettuce is of interest because it was originally cultivated as an oil seed crop (its leaves may also have been used), but its most important centre of production is now in California. Here iceberg lettuces have developed which are capable of being trucked for 100’s of miles to provide crisp leaves for salads and garnish for hamburgers. Some crops have moved from their centres as” weeds”, for example oats. They have subsequently become domesticated in areas with climates that have not suited the original crop but have suited the weed species.
Crops that move and move again!
Taking a very specific example navy beans. This is one of the many different forms of Phaseolus vulgaris the common bean that have been selected by man following their movement from the centre of origin in Mexico. The common bean was brought to by explorers from different European countries. Notably the Portuguese brought them to Europe and Africa in connection with the slave trade. It has been suggested that Jersey has played a significant role in the story of the humble baked bean. Sir Walter Raleigh was governor of Jersey and it is possible that he introduced it to the island. It became part of the Jersey cuisine. In the nineteenth century common beans were taken back to the New World by European settlers including fishermen from Jersey. They took the “navy bean” with them and also the information about the dishes that they used them in. One of these dishes became popular around Boston as the “Boston baked bean”. Heinz saw the potential of canning this dish. It proved to be a cheap and nutritious food for feeding troops in the First and Second World War. British servicemen returning from the Second World War brought back their liking for baked beans and this lead to baked beans replacing other bean dishes in the post war period in Britain.