More interesting but perhaps less known is the history of the contacts between Africa and Asia (beyond the Near East) in very early times. Africa gave to Asia a number of domesticated plants. But Africa also received from Asia not only the Near Eastern cultigens (wheats, barleys, and so on) but also plants transmitted from tropical South-East Asia. It does seem very probable that the bananas, the greater ya m (Dioscorea alata L.), the taro (Çolocasia esculenta L . Schott.) and possibly the sugar cane (Saccarum officinarum L.) arrived on African shores perhaps by way of south-western Arabia and East Africa, or perhaps brought in by early navigators landing on the coast of South-East Africa. Som e of these cultivated plants native to Asia, notably the bananas, enabled agriculture to gain an easier foothold in the tropical forest regions of Africa.
A good example of this African-Asian exchange is the case of the sorghums. In Asia, there exist today cultivated sorghums of African origin other than those already mentioned, especially, for example, S. bicolor Moenc h which seems to have originated through crossing cultigens deriving from S. aethiopicum on the one hand and on the other from the wild species S. sudanense. This S. bicolor ma y be linked in particular to the S. dochna Snowd. of India, Arabia and Burma , re-introduced into Africa in more recent times, the 5 . miliforme Snowd. of India recently introduced into Kenya, and the sorghums of East Africa. Yet another cultivated sorghum, S. nervosum Bess., seems related to S. aethiopicum and to 5 . bicolor, and it seems that the sorghums of Burm a and also of China may , with others, be related to it. Without going into the inevitably complex details of this genetic cocktail, w e can simply state that there are plenty of indications of ancient contacts between the sorghums of Africa and those of Asia. Everything points to very old relationships and exchanges of plant material between the eastern parts of Africa and Asia. Certainly w e know that in Africa, in precolonial times, there existed a numbe r of cultivated plant species which had their origin in tropical South-East Asia. We have already mentioned that it was perhaps easier for agriculture to gain a foothold in the African forest as a result of the appearance of cultivated species such as bananas and taro which had their origin in the wet, tropical forests of South-East Asia and the East Indies. It was from here that the early migrants set out for Madagascar and the East African coast, taking with them a number of their domesticated plants.
