Paranthropus
Paranthropus is a genus of extinct hominin which contains two widely accepted species: P. robustus and P. boisei. However, the validity of Paranthropus is contested, and it is sometimes considered to be synonymous with Australopithecus. They are also referred to as the robust australopithecines. They lived between approximately 2.9 and at least 1 million years ago from the end of the Pliocene to the Middle Pleistocene.
Paranthropus is characterised by robust skulls, with a prominent gorilla-like sagittal crest along the midline—which suggest strong chewing muscles—and broad, herbivorous teeth used for grinding. However, they likely preferred soft food over tough and hard food. Typically, Paranthropus species were generalist feeders, but while P. robustus was likely an omnivore, P. boisei seems to have been herbivorous, possibly preferring abundant bulbotubers. Paranthropoids were bipeds. Despite their robust heads, they had comparatively small bodies. Average weight and height are estimated to be at for P. robustus males, at for P. boisei males, at for P. robustus females, and at for P. boisei females.
They were possibly polygamous and patrilocal, but there are no modern analogues for australopithecine societies. They are associated with bone tools and contested as the earliest evidence of fire usage. They typically inhabited woodlands, and coexisted with some early human species, namely A. africanus, H. habilis and H. erectus. They were preyed upon by the large carnivores of the time, specifically crocodiles, leopards, sabertoothed cats and hyenas. Paranthropus, specifically P. boisei, was also the likely origin of genital herpes in modern humans.
Taxonomy
Species
''P. robustus''
The genus Paranthropus was first erected by Scottish-South African palaeontologist Robert Broom in 1938, with the type species P. robustus. "Paranthropus" derives from Ancient Greek παρα para beside or alongside; and άνθρωπος ánthropos man. The type specimen, a male braincase, TM 1517, was discovered by schoolboy Gert Terblanche at the Kromdraai fossil site, about southwest of Pretoria, South Africa. By 1988, at least six individuals were unearthed in around the same area, now known as the Cradle of Humankind.In 1948, at Swartkrans Cave, in about the same vicinity as Kromdraai, Broom and South African palaeontologist John Talbot Robinson described P. crassidens based on a subadult jaw, SK 6. He believed later Paranthropus were morphologically distinct from earlier Paranthropus in the cave—that is, the Swartkrans Paranthropus were reproductively isolated from Kromdraai Paranthropus and the former eventually speciated. By 1988, several specimens from Swartkrans had been placed into P. crassidens. However, this has since been synonymised with P. robustus as the two populations do not seem to be very distinct.
''P. boisei''
In 1959, P. boisei was discovered by Mary Leakey at Olduvai Gorge, Tanzania. Her husband Louis named it Zinjanthropus boisei because he believed it differed greatly from Paranthropus and Australopithecus. The name derives from "Zinj", an ancient Arabic word for the coast of East Africa, and "boisei", referring to their financial benefactor Charles Watson Boise. However, this genus was rejected at Mr. Leakey's presentation before the 4th Pan-African Congress on Prehistory, as it was based on a single specimen. The discovery of the Peninj Mandible made the Leakeys reclassify their species as Australopithecus boisei in 1964, but in 1967, South African palaeoanthropologist Phillip V. Tobias subsumed it into Australopithecus as A. boisei. However, as more specimens were found, the combination Paranthropus boisei became more popular.It is debated whether the wide range of variation in jaw size indicates simply sexual dimorphism or a grounds for identifying a new species. It could be explained as groundmass filling in cracks naturally formed after death, inflating the perceived size of the bone. P. boisei also has a notably wide range of variation in skull anatomy, but these features likely have no taxonomic bearing.
''P. aethiopicus''
In 1968, French palaeontologists Camille Arambourg and Yves Coppens described "Paraustralopithecus aethiopicus" based on a toothless mandible from the Shungura Formation, Ethiopia. In 1976, American anthropologist Francis Clark Howell and Breton anthropologist Yves Coppens reclassified it as A. africanus. In 1986, after the discovery of the skull KNM WT 17000 by English anthropologist Alan Walker and Richard Leakey classified it into Paranthropus as P. aethiopicus. There is debate whether this is synonymous with P. boisei, the main argument for separation being the skull seems less adapted for chewing tough vegetation.In 1989, palaeoartist and zoologist Walter Ferguson reclassified KNM WT 17000 into a new species, walkeri, because he considered the skull's species designation questionable as it comprised the skull whereas the holotype of P. aethiopicus comprised only the mandible. Ferguson's classification is almost universally ignored, and is considered to be synonymous with P. aethiopicus.
Others
In 2015, Ethiopian palaeoanthropologist Yohannes Haile-Selassie and colleagues described the 3.5–3.2 Ma A. deyiremeda based on three jawbones from the Afar Region, Ethiopia. They noted that, though it shares many similarities with Paranthropus, it may not have been closely related because it lacked enlarged molars which characterize the genus. Nonetheless, in 2018, independent researcher Johan Nygren recommended moving it to Paranthropus based on dental and presumed dietary similarity.A 1.4 million year old jaw, designated "SK 15" that was discovered in 1949 in Swartkrans, initially named Telanthropus capensis and later attributed to Homo ergaster was suggested to belong to the genus Parathropus by palaeoanthropologist Clément Zanolli, based on high-resolution X-ray scans and virtual 3D modeling.
Validity
In 1951, American anthropologists Sherwood Washburn and Bruce D. Patterson were the first to suggest that Paranthropus should be considered a junior synonym of Australopithecus as the former was only known from fragmentary remains at the time, and dental differences were too minute to serve as justification. In face of calls for subsumation, Leakey and Robinson continued defending its validity. Various other authors were still unsure until more complete remains were found. Paranthropus is sometimes classified as a subgenus of Australopithecus.There is currently no clear consensus on the validity of Paranthropus. The argument rests upon whether the genus is monophyletic—is composed of a common ancestor and all of its descendants—and the argument against monophyly says that P. robustus and P. boisei evolved similar gorilla-like heads independently of each other by coincidence, as chewing adaptations in hominins evolve very rapidly and multiple times at various points in the family tree. In 1999, a chimp-like ulna forearm bone was assigned to P. boisei, the first discovered ulna of the species, which was markedly different from P. robustus ulnae, which could suggest paraphyly.
Evolution
P. aethiopicus is the earliest member of the genus, with the oldest remains, from the Ethiopian Omo Kibish Formation, dated to 2.6 mya at the end of the Pliocene. It is sometimes regarded as the direct ancestor of P. boisei and P. robustus. It is possible that P. aethiopicus evolved even earlier, up to 3.3 mya, on the expansive Kenyan floodplains of the time. The oldest P. boisei remains date to about 2.3 mya from Malema, Malawi. P. boisei changed remarkably little over its nearly one-million-year existence. Paranthropus had spread into South Africa by 2 mya with the earliest P. robustus remains.It is sometimes suggested that Paranthropus and Homo are sister taxa, both evolving from Australopithecus. This may have occurred during a drying trend 2.8–2.5 mya in the Great Rift Valley, which caused the retreat of woodland environments in favor of open savanna, with forests growing only along rivers and lakes. Homo evolved in the former, and Paranthropus in the latter riparian environment. However, the classifications of Australopithecus species is problematic.
According to a 2025 study of palaeoproteomics of Paranthropus teeth from Swartkrans Cave was able to assign the individual teeth to sex and identify patterns of diversity suggesting the existence of multiple populations.
Evolutionary tree according to a 2019 study:
Description
Skull
Paranthropus had a massively built, tall and flat skull, with a prominent gorilla-like sagittal crest along the midline which anchored large temporalis muscles used in chewing. Like other australopithecines, Paranthropus exhibited sexual dimorphism, with males notably larger than females. They had large molars with a relatively thick tooth enamel coating, and comparatively small incisors, possibly adaptations to processing abrasive foods. The teeth of P. aethiopicus developed faster than those of P. boisei.Paranthropus had adaptations to the skull to resist large bite loads while feeding, namely the expansive squamosal sutures. The notably thick palate was once thought to have been an adaptation to resist a high bite force, but is better explained as a byproduct of facial lengthening and nasal anatomy.
In P. boisei, the jaw hinge was adapted to grinding food side-to-side, which is better at processing the starchy abrasive foods that likely made up the bulk of its diet. P. robustus may have chewed in a front-to-back direction instead, and had less exaggerated anatomical features than P. boisei as it perhaps did not require them with this kind of chewing strategy. This may have also allowed P. robustus to better process tougher foods.
The braincase volume averaged about, comparable to gracile australopithecines, but smaller than Homo. Modern human brain volume averages for men and for women.