The Olduvai Gorge is an archeological site situated on a series of fault lines, where centuries of erosion have revealed fossils and remnants of early mankind. As early as 1911, a German professor found some fossil bones while looking for butterflies in Olduvai Gorge. In a later expedition, the Leakeys collected skull fragments, a skull, and bones determined to be approximately 2 million years old. Tools and hunting weapons from 1 to 1.5 million years ago were also discovered in Olduvai Gorge. Another exciting find were the famous footprints of a man, woman and child at Laetoli, near Olduvai. These and other discoveries provide more evidence to the theory that at least three hominid species were in this region over 2 million years ago.