The trek down the western face of the Ngorongoro highlands offered yet another example of Tanzania's striking environmental diversity. The cool, grassy highlands, dotted with Maasai bomas and herds of cattle and goats, gradually gave way to rocky, whistling thorn acacia-speckled foothills, which then yielded to the parched, dusty flats of the southern Serengeti. Our goal this day was to visit the Olduvai Gorge Museum and the gorge itself, followed by explorations at Nasera Rock and the nearby Magnetic Shifting Sand Dunes.

Olduvai Gorge ranks among the world's most important paleoanthropological sites. Within the ravine, seasonal torrents of rainwater from the nearby Ngorongoro highlands expose geological layers containing extraordinary evidence of animal and human evolution spanning nearly two million years. It was here, in the mid-20th century, that Louis and Mary Leakey discovered fossils of Homo habilis (about 2.0 million years ago), Paranthropus boisei (about 1.8 million years ago), and an astonishing array of stone tools belonging to the Oldowan and later Acheulean industries of Homo erectus and early Homo sapiens. Over the decades, thousands of animal fossils have also been uncovered, documenting the shifting ecosystems in which early humans lived. Even today, Olduvai remains an active research site, its eroded ravines continually revealing new windows into the deep past. When we arrived, no excavations were in progress, but we met with an Olduvai Gorge Museum docent at the very site of the Leakeys' discoveries and then toured the museum’s exhibits.