Overview:

Australopithecus anamensis has a combination of traits found in both apes and humans. The upper end of the tibia (shin bone) shows an expanded area of bone and a human-like orientation of the ankle joint, indicative of regular bipedal walking (support of body weight on one leg at the time). Long forearms and features of the wrist bones suggest these individuals probably climbed trees as well. The cranium combines some more ancestral features, such as a protruding face and a long and narrow braincase, with some more derived features, such as forwardly projecting cheekbones similar to Paranthropus.

History of Discovery:

In 1965, a research team led by Bryan Patterson from Harvard University discovered a single arm bone (KNM-KP 271) of an early human at the site of Kanapoi in northern Kenya. But without additional human fossils, Patterson could not confidently identify the species to which it belonged. In 1994, a research team led by paleoanthropologist Meave Leakey found numerous teeth and fragments of bone at the same site. Leakey and her colleagues determined that the fossils were those of a very primitive hominin and they named a new species called Australopithecus anamensis (‘anam’ means ‘lake’ in the Turkana lanaguage). Researchers have since found other Au. anamensis fossils at nearby sites (including Allia Bay), all of which date between about 4.2 million and 3.9 million years old. In 2019, a team led by Yohannes Haile-Selassie announced a nearly complete Au. anamensis cranium from Woranso-Mille, Ethiopia, dated to 3.8 million years ago.

How They Survived:

Australopithecus anamensis individuals had thickly-built, long, narrow jaws with their side rows of teeth arranged in parallel lines.  Their strong jaws combined with heavily enameled teeth suggest Au. anamensis individuals may at times have eaten hard, abrasive foods, but they likely were plant-eaters in general, relying on both fruits and tough foods such as nuts.  The sites where remains of Au. anamensis have been found were forests and woodlands that grew around lakes.

Evolutionary Tree Information:

Jaw remains suggest that this species was the direct ancestor of Australopithecus afarensis, and possibly the direct descendent of a species of Ardipithecus. However, a new cranium announced in 2019 dated to 3.8 million years ago indicates that this species overlapped in time with Australopithecus afarensis for at least 100,000 years.

Questions:

We don’t know everything about our early ancestors—but we keep learning more! Paleoanthropologists are constantly in the field, excavating new areas with groundbreaking technology, and continually filling in some of the gaps about our understanding of human evolution.

Below are some of the still unanswered questions about Australopithecus anamensis that may be answered with future discoveries:

1. Is Au. anamensis a separate species from Au. afarensis? Many scientists think the fossil material of Au. anamensis and Au. afarensis represents a single lineage that evolved through time, although the 2019 announcement of the MRD Au. anamensis cranium indicated temporal overlap between these two species.
2. Is Au. amanensis a direct descendant of the 4.4 million year old species Ardipithecus ramidus?

References:

First paper:

Leakey, M.G., Feibel, C.S., McDougall, I., Walker, A., 1995. New four-million-year-old hominid species from Kanapoi and Allia Bay, Kenya. Nature 376,565-571.

Other recommended reading:

Leakey, M.G., Feibel, C.S., McDougall, I., Ward, C., Walker, A., 1998. New specimens and confirmation of an early age for Australopithecus anamensis. Nature 393, 62-66.

Ward, C. Leakey, M., Walker, A., 1999. The new hominid species Australopithecus anamensis. Evolutionary Anthropology 7, 197-205.

White, T.D, WoldeGabriel, G., Asfaw, B., Ambrose, S., Beyene, Y., Bernor, R.L., Boisserie, J.-R., Currie, B., Gilbert, H., Haile-Selassie, Y., Hart, W.K., Hlusko, L.J., Howell, F.C., Kono, R.T., Lehmann, T., Louchart, A., Lovejoy, C.O., Renne, P.R., Saegusa, H.,  Vrba, E.S., Wesselman, H., Suwa, G.,  2006. Asa Issie, Aramis and the origin of Australopithecus. Nature 440, 883-889.

Haile-Selassie, Y., Melillo, S.M., Vazzana, A., Banazzi, S., Ryan, T.M. 2019. A 3.8 million-year-old hominin cranium from Woranso-Mille, Ethiopia. Nature 573, 214-221.