The Olduvai Gorge or Oldupai Gorge is commonly referred to as "The Cradle of Mankind." It is a steep-sided ravine in the Great Rift Valley, which stretches along eastern Africa. Olduvai is in the eastern Serengeti Plains in northern Tanzania and is about long. The gorge is named after the Maasai word for the wild sisal plant Sansevieria ehrenbergii, commonly called Oldupaai.
The stratigraphy is extremely deep and layers of volcanic ash and stones allow radiometric dating of the embedded artifacts, mostly through potassium-argon dating. The first artifacts in Olduvai (pebble tools and choppers) date to circa 2 million years ago but fossil remains of human ancestors have been found from as long as 2.5 million years ago.
The earliest archaeological deposit, known as Bed I, has produced evidence of campsites and living floors along with stone tools made of flakes from local basalt and quartz. Since this is the site where these kinds of tools were first discovered, these tools are called Oldowan. It is now thought that the Oldowan toolmaking tradition started about 2.6 million years ago. Bones from this layer are not of modern humans but primitive hominid forms of Paranthropus boisei and the first discovered specimens of Homo habilis.
Beds III and IV have produced Acheulean tools and fossil bones from more than 600,000 years ago.
Beds above these contained tools from a Kenya-Capsian industry made by modern humans and are termed the Masek Beds (600,000 to 400,000 years ago), the Ndutu Beds (400,000 to 32,000 years ago), and the Naisiusiu Beds (22,000 to 15,000 years ago).
Also located on the rim of the Gorge is the Olduvai Gorge Museum. This Museum presents exhibitions pertaining to the Gorge's history.
Olduvai is also the theme of the Olduvai theory, which states that industrial civilization will have a lifetime of less than or equal to 100 years.
The variant "Oldupai" is the Maasai word for the wild Sisal plant that grows in the gorge; some claim the more common spelling "Olduvai" is the result of a mis-hearing of the word by colonial visitors. The latter spelling is not used locally.