填空题.The hunter-gatherer tribes that today live like our prehistoric human 1 ancestors consume primarily a vegetable diet supplementing with animal foods. 2 An analysis of 58 societies of modern hunter-gatherers, including the Kung of southern Africa, revealed that one-half emphasize gathering plant foods, one-third concentrate on fishing, and only one-sixth are primarily hunters. Overall, two-thirds and more of the hunter-gatherer's calories come from 3 plants. Detailed studies of the Kung by the food scientists at the University of London, showed that gathering is a more productive source of food than is hunting. An hour of hunting yields in average about 100 edible 4 calories, as an hour of gathering produces 240. 5 Plant foods provide for 60 percent to 80 percent of the Kung diet, and no 6 one goes hungry when the hunt fails. Interestingly, if they escape fatal infections or accidents, these contemporary aborigines live to old ages despite of the absence 7 of medical care. They experience no obesity, no middle-aged spread, little dental decay, no high blood pressure, no heart disease, and their blood cholesterol levels are very low (about half of the average American adult). 8 If no one is suggesting that we return to an aboriginal life style, we certainly 9 could use their eating habits as a model for healthier diet. 10