Paranthropus robustus

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Paranthropus robustus
Fossil range: Pliocene-Pleistocene

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Primates
Family:	Hominidae
Subfamily:	Homininae
Genus:	Paranthropus
Species:	P. robustus

Binomial name

†Paranthropus robustus
Broom, 1938

Paranthropus robustus was originally discovered in Southern Africa in 1938. The development of P. robustus, namely in cranial features, seemed to be aimed in the direction of a "heavy-chewing complex". Because of the definitive traits that are associated with this robust line of australopithecine, anthropologist Robert Broom erected the genus Paranthropus and placed this species into it.

Paranthropus robustus is generally dated to have lived between 2.0 and 1.2 million years ago. P. robustus had large dorsal crests, jaws, and jaw muscles that were adapted to serve in the dry environment that they lived in.

After Raymond Dart’s discovery of Australopithecus africanus, Broom had been in favour of Dart's claims about Australopithecus africanus being an ancestor of Homo sapiens. Broom was a Scottish doctor then working in South Africa who began making his own excavation in Southern Africa to find more specimens, which Dart had found earlier. In 1938, at 70 years old, Broom, excavating at Swartkrans, South Africa discovered pieces of a skull and teeth which resembled Dart's Australopithecus africanus find, but the skull had some "robust" characteristics. The fossils included parts of a skull and teeth; all dated to 2 million years old. Fossil sites found on Paranthropus robustus are found only in South Africa in Kromdraai and Swartkrans. In the caves near Swartkrans, the remains of 130 individuals were discovered. The study made on the dentation of the hominins revealed that the average P. robustus rarely lived past 17 years of age.

Paranthropus robustus became the first "robust" species of hominid ever uncovered well before P. boisei and P. aethiopicus. Broom's first discovery of P. robustus had been the first discovery of a robust australopithecine and the second australopithecine after Australopithecus africanus, which Dart discovered. Broom's work on the australopithecines showed that the evolution trail leading to Homo sapiens was not just a straight line, but was one of rich diversity.

[edit] Morphology

Typical of robust australopithecines, P. robustus had a head shaped a bit like a gorilla's with a more massive built jaw and teeth in comparison to hominins within the Homo lineage. Broom also noted the sagital crest that runs from the top of the skull acts as an anchor for large chewing muscles. The DNH 7 skull of Paranthropus robustus, "Eurydice", was discovered in 1994 at the Drimolen Cave in Southern Africa by Andre Keyser, and is dated to 2.3 million years old, possibly belonging to a female.

The teeth of these primates were larger and thicker than any gracile australopithecine found, due to the morphology differences Broom originally designated his find as Australopithecus robustus. On the skull, a bony ridge is located above from the front to back indicating where the jaw muscles joined. P. robustus males may have stood only 4 feet tall and weighed 54 kg (120 lb) while females stood just under 1 meter (3 feet 2 inches) tall and weighed only 40 kg (90 lb). Clearly there was a large sexual dimorphism between males and females. The teeth found on P. robustus are almost as large as those of P. boisei.

Broom analyzed his findings carefully and noted the differences in the molar teeth size which resembled a gorilla's a bit more than a human's. Other P. robustus remains have been found in Southern Africa. The average brain size of P. robustus measured to only 410 and 530 cc, about as large as a chimpanzee's. P robustus had a diet of hard gritty foods such as nuts and tubers since they lived in open woodland and savanna.