Why are the fossils so rich in that particular area of Africa?
Donald Johanson: The area of Africa where I worked since the early 1970s is known as the Great Rift Valley. The Great Rift Valley of East Africa has been developing because the horn of Africa has been slowly moving away from the bulk of Africa because of continental drift. As it has been doing so, it’s been thinning the earth’s crust and allowing volcanoes to emerge. It has had areas of subsidence, where you have had lakes and rivers. This has been an ideal environment for animals to die, fall into these lakes and rivers, and be slowly transformed into fossils. The same processes of earth movements which were going on to create this environment are still going on, and promoting a great deal of erosion. The same processes that brought about their preservation are bringing about their re-exposure on the surface. It’s an ideal environment in which to find these fossils. What was it like for Lucy? Do you have a picture of what the earth looked like when she walked upon it? Donald Johanson:
