The Effects of Domestication on Certain Seed and Fiber Properties of Perennial Forms of Cotton, Gossypium hirsutum L.

A consideration of a wide range of native forms of Gossypium birsutum leads to the conclusion that they can be grouped into five discrete categories: A-"wild", B-semi-feral, C-commensal, D-primitive cultigens, and E-improved types. They constitute a sequence A through E in which the effects of human selection should become progressively greater. Certain seed and fiber properties seem to have been influenced by domestication. Prompt seed germination, which is infrequent in "wild" forms, becomes progressively more common with increasing domestication. In the Caribbean area seed size has been approximately doubled, and this, in turn, has apparently been associated with a threefold increase in lint index and an 80 per cent increase in mean fiber length. An attempt has been made to correlate these changes with known events in the imperfectly known historical and archaeological record in the Caribbean. The final step (from D to E) is known to have taken place during the last 50 years. The differentiation of Categories B, C and D was most likely initiated in mid-eighteenth century when cotton was grown and exported to European markets. It is suggested that the earliest step from A to B may have been accomplished between the time of the Spanish Conquest (15th-16th centuries) and mid-eighteenth century. On this interpretation the types in Category A would be feral forms descended from pre-Columbian cultigens. Alternatively, if Category A types have never been cultivated, the step from A to B would be extended back in time to the origin of settled cultures in the Caribbean (between 1000 B.C. and 300 A.D.). These findings are related to the much older records of domestication which have recently been obtained in Meso-America.