It is a unique natural laboratory for the study of human origins and evolution and a number of fossils of the earliest hominins, particularly of the Australopithecines, as well as some of the oldest known Olduwan stone artifacts, have been found at the site—all of late Miocene, the Pliocene, and the very early Pleistocene times, that is, about 5.6 million years ago (mya) to 2.5 mya.

[2][3] [4] It is broadly thought that the divergence of the lines of the earliest humans (hominins) and of chimpanzees (hominids) was completed near the beginning of that time range, or sometime between seven and five mya.

However, the larger community of scientists provide several estimates for periods of divergence that imply a greater range for this event, see CHLCA: human-chimpanzee split.

Australopithecus garhi fossils are dated as recent as the very early Pleistocene, or 2.5 mya; fossils of Homo erectus in the Daka member at the site (at 1 mya) and Homo sapiens idaltu (at 160 ka ago) are found in the middle and late Pleistocene.

Fossil remains of other vertebrates found with the hominins, including the cane rat, further suggest such an environment.