Contrasting dissemination patterns of diploid cultivated cotton species Gossypium herbaceum L. and G. arboreum L. in Antiquity
The textile use of cotton fibers from sister species Gossypium arboreum L. (Tree Cotton) and G. herbaceum L. (Levant Cotton) began, respectively, in Asia in the eighth millennium BP and in Africa in the third millennium BP and probably earlier. Archaeological data show that cotton cultivation spread in the Antiquity over most tropical and subtropical regions suitable for agriculture in Afroeurasia. The geographical expansions of the two Old World cotton species appear very contrasted, in terms of their chronologies, in terms of the areas conquered, and as for their speed of diffusion. G. arboreum spread over humid or sub-humid regions of southern, western and eastern Asia at ca. 0.8 to 1.7 km/yr, a rate close to that estimated for wheat from the Fertile Crescent to northwestern Europe during Antiquity, while G. herbaceum spread over arid to sub-arid regions of Africa and western and central Asia, much later and more than five times faster than G. arboreum. The very high speed of diffusion of G. herbaceum can be explained by the context and by the agricultural adaptations of this species but also leads to revisit the history of its domestication and beginning of cultivation.