Australopithecus anamensis -- KNM-KP 29285

Australopithecus anamensis -- KNM-KP 29285

This partial tibia, which dates to about 4.1 million years ago, was found at the Kanapoi site in Kenya.

A paleoanthropological research team headed by Meave Leakey

KNM-KP 29285

Kenya

Kanapoi

1994

about 4.1 million years ago

⁴⁰Ar/³⁹Ar dating of the volcanic ash layer in which it was found

This specimen, which consists of the proximal and distal ends of a right tibia, provides the earliest evidence for bipedalism in Australopithecus anamensis. The proximal condyles, which articulate with the distal end of the femur, are concaved like the condyles seen in anatomically modern Homo sapiens. Additionally, similar to modern humans, the proximal tibia is wider near the knee joint to allow the deposit of extra spongy bone, which acts as a shock absorber during bipedal locomotion. This extra deposit of spongy bone can also be seen in the medial malleolus, which articulates with the ankle.

Overall, the partial tiba is more human-like than it is ape-like. The fact that the shock-absorbing mechanisms in Au. anamensis so closely mirror the same mechanisms seen in modern humans is what led Leakey, Kimeu, and other paloeanthropologists to believe that this species was a habitual biped. 

Conroy, Glenn C., and Herman Pontzer. Reconstructing Human Origins: A Modern Synthesis. 3rd ed., New York & London, W. W. Norton & Company, Inc., 2012, pp. 220-21.

Johanson, Donald, and Blake Edgar. From Lucy to Language. New York, Nevraumont Publishing Company, 2006, p. 39.

Johanson, Donald, and Blake Edgar. From Lucy to Language. New York, Nevraumont Publishing Company, 2006, p. 129-30.

Hefner, Joseph. "Australopithecus anamensis." Michigan State University, 23 Feb. 2012, East Lansing.

"KNM-KP 29285." What Does it Mean to be Human?, 9 Feb. 2016, humanorigins.si.edu/evidence/human-fossils/fossils/knm-kp-29285. Accessed 12 Apr. 2017.