Social scientist Luke Kemp analyzed dozens of civilizations—which he defined as "a society with agriculture, multiple cities, military dominance in its geographical region and a continuous political structure"—from 3000 B.C. to 600 A.D. and calculated that the average life span of a civilization is close to 340 years. Of these, the most durable were the Kushite Kingdom in Northeast Africa (1,150 years), the Aksumite Empire in Africa (1,100 years), and the Vedic Civilization in South Asia and the Olmecs in Mesoamerica (both 1,000 years), while the shortest-lived were the Nanda Empire in India (24) and the Qin Dynasty in China (14).