These beds reveal a record of a very important time period (1.79 - 1.15 million years ago), a record that contains evidence of critical changes in the area's fauna, stone tools and climate, such as the disappearance of Homo habilis, a very early hominin and possible human ancestor, and the emergence of Homo erectus, a later hominin considered to be the earliest human ancestor to exit Africa and spread across Eurasia.
Scientists suggest that these same beds may include evidence of the long-sought transition from the more primitive Oldowan stone tools to the appearance of the more advanced Acheulean tools.
Homo erectus is widely thought to be the first species to venture out of Africa to populate the Middle East/Eurasia.
British Museum, Discott, Wikimedia Commons (Tanzania) 22 December 2012 An international team of researchers have returned to Olduvai Gorge in Tanzania to unravel the mystery of how humans transitioned from the first stone tool technology to a more sophisticated industry.
To do this successfully, they said, required extreme dorsiflexion, or bending the foot upward toward the shin to a degree not normally possible among most modern humans.
"We hypothesized that a soft-tissue mechanism might enable such extreme dorsiflexion," wrote the authors in their study report.
The implications for our possible early human ancestors, such as the species Australopithecus afarensis, are significant.
It demonstrated that a foot and ankle bone structure adapted primarily for walking upright on land does not necessarily exclude climbing as a behaviorally habitual means of mobility for survival.
It was first discovered by Donald Johanson and colleagues in the Afar region of Ethiopia with the recovery of the partial skeleton of a 3.2 million-year-old specimen they named "Lucy".
The find has represented a possible benchmark in human evolution for decades.
The Oldowan is considered to have been made and used during the Lower Paleolithic, from 2.6 to 1.7 million years ago, whereas the Acheulean emerged about 1.76 million years ago and was used by early humans up to about 300,000 years ago or later.
To find answers, the team will be reappraising the chronological stratigraphy of Bed II, known to have yielded previous significant finds, and will be re-excavating some of the later beds of the best known fossil and stone tool sites.