How and why did variation in skin color develop in modern humans ( Homo sapiens )? What metals and minerals are mined in and exported from Africa?

(A) Identify FIVE of the following in one or two sentences (5 x 4 = 20 points)

Homo erectus                          Lactose tolerance                                t’eff 

Khoisan                                  Shifting cultivation                            Sahel

Malaria                                   Blombos cave