July The Olduvai Gorge (see p. ) was first ‘discovered’ in the early twentieth century by a German butterfly collector. However, Olduvai has come to be identified with Mary and Louis Leakey, who worked here for over years. It was Mary Leakey who directed archaeological excavations at Olduvai and Laetoli and she made some of the most exciting discoveries.
This is what Louis Leakey wrote about one of their most remarkable finds: ‘ That morning I woke with a headache and a slight fever. Reluctantly, I agreed to spend the day in camp.With one of us out of commission, it was even more vital for the other to continue the work, for our precarious seven-week season was running out. So Mary departed for the diggings with Sally and Toots [two of their dogs] in the Land-Rover [a jeep-like vehicle], and I settled back to a restless day off. Some time later – perhaps I dozed off – I heard the Land-Rover coming up fast to camp.
I had a momentary vision of Mary stung by one of our hundreds of resident scorpions or bitten by a snake that had slipped past the dogs. The Land-Rover rattled to a stop, and I heard Mary’s voice calling over and over: “I’ve got him! I've got him! I’ve got him!” Still groggy from the headache, I couldn’t make her out.
“Got what? Are you hurt?” I asked. “Him, the man! Our man,” Mary said.
“The one we’ve been looking for years. Come quick, I’ve found his teeth!” ’ – From ‘Finding the World's Earliest Man’, by L.S.B. Leakey, National Geographic , (September ). The remains of early humans have been classified into different species.
These are often distinguished from one another on the basis of differences in bone structure. For instance, species of early humans are differentiated in terms of their skull size and distinctive jaws (see illustration on p. ). These characteristics may have evolved due to what has been called the positive feedback mechanism.
THE POSITIVE FEEDBACK MECHANISM The arrows pointing towards a box indicate the