Australopithecus robustus

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2.1-1.6 Million years ago

The species name "robustus" was chosen to describe the skull, jaw, and teeth, which were much more dense and thicker than what was seen in previous species(1). There were also many more ridges and crests located on the skull(2). Its front teeth were smaller, but the molars in the back were larger than previous species(3). This trend is continually seen throughout the human evolution cycle. These dental characteristic hint that their diet consisted of tough foods that required a lot of grinding and chewing from those lower molars(3). A new advancement in the Australopithecus robustus was the presence of a "sagittal crest". This is a ridge that runs from front to back on top of the skull in which muscles are attached(3). These muscles aid in moving the jaw so that chewing is possible. As more muscle is formed more powerful chewing is possible.

Australopithecus robustus skull.

Ardipithecus ramidus	Australopithecus afarnensis	Australopithecus anamensis	Australopithecus africanus	Australopithecus boisei
Homo habilis	Homo erectus	Homo sapiens (archaic)	Homo sapiens neanderthalensis	Homo sapiens (modern)

References:

1. Public Broadcasting Station, 1998, Human Evolution, http://www.pbs.org/wgbh/aso/tryit/evolution/ (November 30, 2001)

2. Poirier, Frank E., 1973, Fossil Man: An Evolutionary Journey, The C.V. Mosby Company, St. Louis, 227 p.

3. Foley, Jim, July 31, 2001, Hominid Species, http://www.talkorigins.org/faqs/homs/species.html (November 29, 2001)