expand southward. Their propagation was accelerated by the adoption of pastoralism and of Iron Age technology. The people living in the south and southwest were hunter-gatherer groups, whose technology involved only minimal use of metal technologies. The development of metal tools during this time period revolutionized agriculture and animal husbandry. This led to the displacement of the hunter-gatherer groups in the east and southeast. The 10th century marked the final expansion of the Bantu in West-Central Africa.Rising population soon made intricate local, regional and foreign commercial nets possible, forming networks that traded mostly in salt, iron and copper. Upemba culture In the 15th century, a society began to develop in the Upemba depression along the banks of the Lualaba River in Katanga. This culture, known as the Upemba, would eventually evolve into the more significant Luba Empire, as well as the Kingdom of Lunda. The process in which the primitive original Upemba society transitioned into the Luba kingdom was gradual and complex. This transition ran without interruption, with several distinct societies developing out of the Upemba culture prior to the genesis of the Luba. Each of these societies based the foundation of their society on that of the one which preceded it (much in the way that many aspects of Roman culture were borrowed from the Greeks). The 5th century saw this societal evolution develop in the area around present day Kamilamba at the Kabambasee, which was followed and replaced by a number of other cultures which were based around the cities of Sanga and Katango. The region in which these cultures appeared is particularly rich in ore and these civilizations began to develop and implement iron and copper technology, in addition to trading in ivory and other goods. The Upemba established a strong commercial demand for their metal technologies and were able to institute a long-range commercial net (the business connections extended over 1500 km, all the way to the Indian Ocean). Additionally, the region was endowed with favorable agricultural conditions and a wealth of fish and game. Its strong economy and food-base allowed the region to become extremely wealthy. So wealthy, in fact, that cities and centralized government based on a chieftain system developed. The political institution of the chieftain became generally accepted and these rulers became increasingly powerful, especially at the end of the 16th century. Effects of geography and climate Additionally, it must be mentioned that,