TOEFL Reading: ETS-TOEFL阅读机经 - 3MW535047TNLGZ13L$

This passage discusses Early Food Production in Sub-Saharan Africa A. Food production started with the cultivation of root plants and developed to include the cultivation of cereal crops. B. Pastoralists who moved south across the Sahara to find suitable land for cattle grazing may have also cultivated some crops for food. C. In order to avoid human and animal sleeping sickness, which posed a danger to herders and cattle, more and more herders took up cultivation. D. Hunter-gatherer groups in eastern and southern Africa raided their herding neighbors to acquire cattle and other domesticated animals. E. By 1500 B.C. cereal agriculture was widespread throughout the savanna belt south of the Sahara, and shifting agriculture was used effectively and widely by farmers. F. Slash-and-burn agriculture was initially rejected by farmers because it was too labor-intensive, but once the technique was improved, it expanded gradually to eastern and southem Africa.