| Paranthropus | |
|---|---|
 | |
| Skull ofP. boisei (MGL 95211) | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Haplorhini |
| Family: | Hominidae |
| Subfamily: | Homininae |
| Tribe: | Hominini |
| Subtribe: | Australopithecina |
| Genus: | †Paranthropus Broom, 1938 |
| Type species | |
| †Paranthropus robustus Broom, 1938 | |
| Species | |
| Synonyms | |
Paranthropus is agenus of extincthominin which contains two widely acceptedspecies:P. robustus andP. boisei. However, the validity ofParanthropus is contested, and it is sometimes considered to besynonymous withAustralopithecus. They are also referred to as therobust australopithecines. They lived between approximately 2.9 and at least 1 million years ago (mya) from the end of thePliocene to theMiddle Pleistocene.
Paranthropus is characterised by robustskulls, with a prominentgorilla-likesagittal 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 whileP. robustus was likely anomnivore,P. boisei seems to have been herbivorous, possibly preferring abundantbulbotubers. Paranthropoids werebipeds. Despite their robust heads, they had comparatively small bodies. Average weight and height are estimated to be 40 kg (88 lb) at 132 cm (4 ft) forP. robustus males, 50 kg (110 lb) at 137 cm (4 ft 6 in) forP. boisei males, 32 kg (71 lb) at 110 cm (3 ft 7 in) forP. robustus females, and 34 kg (75 lb) at 124 cm (4 ft 1 in) forP. boisei females.
They were possiblypolygamous andpatrilocal, 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, namelyA. africanus,H. habilis andH. erectus. They were preyed upon by the large carnivores of the time, specifically crocodiles, leopards,sabertoothed cats and hyenas.Paranthropus, specificallyP. boisei, was also the likely origin ofgenital herpes in modern humans.[1]
The genusParanthropus was first erected by Scottish-South AfricanpalaeontologistRobert Broom in 1938, with thetype speciesP. robustus.[2] "Paranthropus" derives fromAncient Greek παραpara beside or alongside; and άνθρωποςánthropos man.[3] Thetype specimen, a male braincase,TM 1517, was discovered by schoolboy Gert Terblanche at theKromdraai fossil site, about 70 km (43 mi) southwest ofPretoria, South Africa.[2] By 1988, at least six individuals were unearthed in around the same area, now known as theCradle of Humankind.[4]
In 1948, atSwartkrans Cave, in about the same vicinity as Kromdraai, Broom and South African palaeontologistJohn Talbot Robinson describedP. crassidens based on a subadult jaw, SK 6. He believed laterParanthropus were morphologically distinct from earlierParanthropus in the cave—that is, the SwartkransParanthropus werereproductively isolated from KromdraaiParanthropus and the former eventuallyspeciated.[5] By 1988, several specimens from Swartkrans had been placed intoP. crassidens. However, this has since been synonymised withP. robustus as the two populations do not seem to be very distinct.[4]
In 1959,P. boisei was discovered byMary Leakey atOlduvai Gorge,Tanzania (specimenOH 5). Her husbandLouis named itZinjanthropus boisei because he believed it differed greatly fromParanthropus andAustralopithecus. The name derives from "Zinj", an ancient Arabic word for the coast of East Africa, and "boisei", referring to their financial benefactorCharles Watson Boise.[6] 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.[7] The discovery of thePeninj Mandible made the Leakeys reclassify their species asAustralopithecus (Zinjanthropus) boisei in 1964,[8] but in 1967, South African palaeoanthropologistPhillip V. Tobias subsumed it intoAustralopithecus asA. boisei. However, as more specimens were found, the combinationParanthropus boisei became more popular.[9]
It is debated whether the wide range of variation in jaw size indicates simplysexual dimorphism or a grounds for identifying a new species. It could be explained asgroundmass filling in cracks naturally formed after death, inflating the perceived size of the bone.[10][11][12]P. boisei also has a notably wide range of variation in skull anatomy, but these features likely have no taxonomic bearing.[13]
In 1968, French palaeontologistsCamille Arambourg andYves Coppens described "Paraustralopithecus aethiopicus" based on a toothless mandible from theShungura Formation, Ethiopia (Omo 18).[14] In 1976, American anthropologistFrancis Clark Howell and Breton anthropologistYves Coppens reclassified it asA. africanus.[15] In 1986, after the discovery of the skullKNM WT 17000 by English anthropologistAlan Walker andRichard Leakey classified it intoParanthropus asP. aethiopicus.[16] There is debate whether this is synonymous withP. boisei,[11] the main argument for separation being the skull seems less adapted for chewing tough vegetation.[12][17]
In 1989, palaeoartist and zoologistWalter 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 ofP. aethiopicus comprised only the mandible.[15] Ferguson's classification is almost universally ignored,[18] and is considered to be synonymous withP. aethiopicus.[19]
In 2015, Ethiopian palaeoanthropologistYohannes Haile-Selassie and colleagues described the 3.5–3.2 MaA. deyiremeda based on three jawbones from theAfar Region, Ethiopia. They noted that, though it shares many similarities withParanthropus, it may not have been closely related because it lacked enlarged molars which characterize the genus.[20] Nonetheless, in 2018, independent researcher Johan Nygren recommended moving it toParanthropus based on dental and presumed dietary similarity.[21]
A 1.4 million year old jaw, designated "SK 15" that was discovered in 1949 inSwartkrans, initially namedTelanthropus capensis and later attributed toHomo ergaster was suggested to belong to the genusParathropus by palaeoanthropologist Clément Zanolli, based on high-resolution X-ray scans and virtual 3D modeling.[22][23]
In 1951, American anthropologistsSherwood Washburn andBruce D. Patterson were the first to suggest thatParanthropus should be considered ajunior synonym ofAustralopithecus as the former was only known from fragmentary remains at the time, and dental differences were too minute to serve as justification.[24] In face of calls for subsumation, Leakey[6] and Robinson[25] continued defending its validity. Various other authors were still unsure until more complete remains were found.[4]Paranthropus is sometimes classified as asubgenus ofAustralopithecus.[26]
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There is currently no clear consensus on the validity ofParanthropus. The argument rests upon whether the genus ismonophyletic—is composed of a common ancestor and all of its descendants—and the argument against monophyly (that the genus isparaphyletic) says thatP. robustus andP. boisei evolved similar gorilla-like heads independently of each other by coincidence (convergent evolution), as chewing adaptations in hominins evolve very rapidly and multiple times at various points in the family tree (homoplasy).[12] In 1999, a chimp-likeulna forearm bone was assigned toP. boisei, the first discovered ulna of the species, which was markedly different fromP. robustus ulnae, which could suggest paraphyly.[27]
P. aethiopicus is the earliest member of the genus, with the oldest remains, from the EthiopianOmo Kibish Formation, dated to 2.6 mya at the end of thePliocene. It is sometimes regarded as the direct ancestor ofP. boisei andP. robustus.[11] It is possible thatP. aethiopicus evolved even earlier, up to 3.3 mya, on the expansive Kenyan floodplains of the time.[28] The oldestP. boisei remains date to about 2.3 mya fromMalema, Malawi.[11]P. boisei changed remarkably little over its nearly one-million-year existence.[29]Paranthropus had spread into South Africa by 2 mya with the earliestP. robustus remains.[17][30][31]
It is sometimes suggested thatParanthropus andHomo aresister taxa, both evolving fromAustralopithecus. This may have occurred during a drying trend 2.8–2.5 mya in theGreat 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, andParanthropus in the latterriparian environment.[28][32][33] However, the classifications ofAustralopithecus species is problematic.[34]
According to a 2025 study ofpalaeoproteomics ofParanthropus teeth fromSwartkrans Cave was able to assign the individual teeth to sex and identify patterns of diversity suggesting the existence of multiple populations.[35]
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Evolutionary tree according to a 2019 study:[34]
Paranthropus had a massively built, tall and flat skull, with a prominentgorilla-likesagittal crest along the midline which anchored largetemporalis muscles used in chewing.[36] Like other australopithecines,Paranthropus exhibited sexual dimorphism, with males notably larger than females.[17][37][38] They had largemolars with a relatively thicktooth enamel coating (post-canine megadontia),[39] and comparatively smallincisors (similar in size to modernhumans),[40] possibly adaptations to processing abrasive foods.[41][42] The teeth ofP. aethiopicus developed faster than those ofP. boisei.[43]
Paranthropus had adaptations to the skull to resist large bite loads while feeding, namely the expansivesquamosal sutures.[44] The notably thickpalate 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.[45]
InP. boisei, thejaw hinge was adapted to grinding food side-to-side (rather than up-and-down in modern humans), which is better at processing thestarchy 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 (lessderived) anatomical features thanP. boisei as it perhaps did not require them with this kind of chewing strategy. This may have also allowedP. robustus to better process tougher foods.[46]
The braincase volume averaged about 500 cm3 (31 cu in), comparable to gracile australopithecines, but smaller thanHomo.[47] Modern human brain volume averages 1,270 cm3 (78 cu in) for men and 1,130 cm3 (69 cu in) for women.[48]
UnlikeP. robustus, the forearms ofP. boisei were heavily built, which might suggest habitualsuspensory behaviour as inorangutans andgibbons.[27][49][50] AP. boiseishoulder blade indicates longinfraspinatus muscles, which is also associated with suspensory behavior.[51] AP. aethiopicus ulna, on the other hand, shows more similarities toHomo thanP. boisei.[50]
Paranthropus werebipeds, and their hips, legs and feet resembleA. afarensis and modern humans.[52][53] The pelvis is similar toA. afarensis, but the hip joints are smaller inP. robustus. The physical similarity implies a similar walking gait.[54] Their modern-humanlike big toe indicates a modern-humanlike foot posture and range of motion, but the more distal ankle joint would have inhibited the modern human toe-offgait cycle. By 1.8 mya,Paranthropus andH. habilis may have achieved about the same grade of bipedality.[55]
In comparison to the large, robust head, the body was rather small. Average weight forP. robustus may have been 40 kg (88 lb) for males and 32 kg (71 lb) for females;[17] and forP. boisei 50 kg (110 lb) for males and 34 kg (75 lb) for females.[17] At Swartkrans Cave Members 1 and 2, about 35% of theP. robustus individuals are estimated to have weighed 28 kg (62 lb), 22% about 43 kg (95 lb), and the remaining 43% bigger than the former but less than 54 kg (119 lb). At Member 3, all individuals were about 45 kg (99 lb).[37] Female weight was about the same in contemporaneousH. erectus, but maleH. erectus were on average 13 kg (28.7 lb) heavier thanP. robustus males.[56]P. robustus sites are oddly dominated by small adults, which could be explained as heightened predation or mortality of the larger males of a group.[57] The largest-knownParanthropus individual was estimated at 54 kg (119 lb).[37]
According to a 1991 study, based onfemur length and using the dimensions of modern humans, male and femaleP. robustus are estimated to have stood on average 132 and 110 cm (4 ft 4 in and 3 ft 7 in), respectively, andP. boisei 137 and 124 cm (4 ft 6 in and 4 ft 1 in). However, the latter estimates are problematic as there were no positively identified maleP. boisei femurs at the time.[38] In 2013, a 1.34 Ma maleP. boisei partial skeleton was estimated to be at least 156 cm (5 ft 1 in) and 50 kg (110 lb).[49]
Paranthropus seems to have had notably high rates ofpitting enamel hypoplasia (PEH), wheretooth enamel formation is spotty instead of mostly uniform. InP. robustus, about 47% ofbaby teeth and 14% of adult teeth were affected, in comparison to about 6.7% and 4.3%, respectively, in any other tested hominin species. The condition of these holes covering the entire tooth is consistent with the modern human ailmentamelogenesis imperfecta. However, since circular holes in enamel coverage are uniform in size, only present on themolar teeth, and have the same severity across individuals, the PEH may have been a genetic condition. It is possible that thecoding-DNA concerned with thickening enamel also left them more vulnerable to PEH.[58]
There have been 10 identified cases ofcavities inP. robustus, indicating a rate similar to modern humans. A molar fromDrimolen, South Africa, showed a cavity on thetooth root, a rare occurrence in fossilgreat apes. In order for cavity-creating bacteria to reach this area, the individual would have had to have also presented eitheralveolar resorption, which is commonly associated withgum disease; or super-eruption of teeth which occurs when teeth become worn down and have to erupt a bit more in order to maintain a proper bite, and this exposed the root. The latter is most likely, and the exposed root seems to have causedhypercementosis to anchor the tooth in place. The cavity seems to have been healing, which may have been caused by a change in diet ormouth microbiome, or the loss of the adjacent molar.[59]
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It was once thoughtP. boisei cracked open nuts with its powerful teeth, giving OH 5 the nickname "Nutcracker Man". However, like gorillas,Paranthropus likely preferred soft foods, but would consume tough or hard food during leaner times, and the powerful jaws were used only in the latter situation.[60] InP. boisei, thick enamel was more likely used to resist abrasive gritty particles rather than to minimize chipping while eating hard foods.[61] In fact, there is a distinct lack of tooth fractures which would have resulted from such activity.[62][63]
Paranthropus were generalist feeders, but diet seems to have ranged dramatically with location. The South AfricanP. robustus appears to have been an omnivore, with a diet similar to contemporaneousHomo[36] and nearly identical to the laterH. ergaster,[64] and subsisted on mainlyC4 savanna plants andC3 forest plants, which could indicate either seasonal shifts in diet or seasonal migration from forest to savanna. In leaner times it may have fallen back on brittle food. It likely also consumed seeds[65][66] and possiblytubers ortermites.[67] A high cavity rate could indicatehoney consumption.[59]
The East AfricanP. boisei, on the other hand, seems to have been largely herbivorous and fed on C4 plants. Its powerful jaws allowed it to consume a wide variety of different plants,[42][68] though it may have largely preferred nutrient-richbulbotubers as these are known to thrive in the well-watered woodlands it is thought to have inhabited. Feeding on these,P. boisei may have been able to meet its daily caloric requirements of approximately 9,700 kJ after about 6 hours of foraging.[69]
JuvenileP. robustus may have relied more on tubers than adults, given the elevated levels ofstrontium compared to adults in teeth from Swartkrans Cave, which, in the area, was most likely sourced from tubers.Dentin exposure on juvenile teeth could indicate early weaning, or a more abrasive diet than adults which wore away thecementum andenamel coatings, or both. It is also possible juveniles were less capable of removing grit from dug-up food rather than purposefully seeking out more abrasive foods.[41]
Oldowan toolkits were uncovered at an excavation site on the Homa Peninsula in western Kenya. Stone tools called "oldowan toolkits" are used to pound and shape other rocks or plant materials. These tools are thought to be between 2.6 and 3 million years old. The stone tools were found near Paranthropus teeth.[70]
Bone tools dating between 2.3 and 0.6 mya have been found in abundance in Swartkrans,[67] Kromdraai andDrimolen caves, and are often associated withP. robustus. ThoughHomo is also known from these caves, their remains are comparatively scarce toParanthropus, makingHomo-attribution unlikely. The tools also cooccur withHomo-associatedOldawan and possiblyAcheulian stone toolindustries. The bone tools were typically sourced from theshaft oflong bones from medium- to large-sized mammals, but tools made sourced frommandibles,ribs and horn cores have also been found. Bone tools have also been found at Oldawan Gorge and directly associated withP. boisei, the youngest dating to 1.34 mya, though a great proportion of other bone tools from here have ambiguous attribution. Stone tools from Kromdraai could possibly be attributed toP. robustus, as noHomo have been found there yet.[30]
The bone tools were not manufactured or purposefully shaped for a task. However, since the bones display no weathering (and were not scavenged randomly), and there is a preference displayed for certain bones, raw materials were likely specifically hand-picked. This could indicate a similar cognitive ability to contemporary Stone AgeHomo.[30]
Bone tools may have been used to cut or process vegetation,[71] or dig uptubers ortermites,[30][67] The form ofP. robustus incisors appear to be intermediate betweenH. erectus and modern humans, which could indicate less food processing done by the teeth due to preparation with simple tools.[41]
Burnt bones were also associated with the inhabitants of Swartkrans, which could indicate some of the earliest fire usage.[72] However, these bones were found in Member 3, whereParanthropus remains are rarer thanH. erectus, and it is also possible the bones were burned in a wildfire and washed into the cave as it is known the bones were not burned onsite.[73][74]
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Given the marked anatomical and physical differences with modern great apes, there may be no modern analogue for australopithecine societies, so comparisons drawn with modern primates will not be entirely accurate.[75][76]
Paranthropus had pronouncedsexual dimorphism, with males notably larger than females, which is commonly correlated with a male-dominatedpolygamous society.P. robustus may have had a harem society similar to modern forest-dwellingsilverback gorillas, where one male has exclusive breeding rights to a group of females, as male-female size disparity is comparable to gorillas (based on facial dimensions), and younger males were less robust than older males (delayed maturity is also exhibited in gorillas).[77]
However, ifP. robustus preferred a savanna habitat, a multi-male society would have been more productive to better defend the troop from predators in the more exposed environment, much like savannababoons. Further, among primates, delayed maturity is also exhibited in therhesus monkey which has a multi-male society, and may not be an accurate indicator of social structure.[76]
A 2011strontium isotope study ofP. robustus teeth from thedolomiteSterkfontein Valley found that, like otherhominins, but unlike other great apes,P. robustus females were more likely to leave their place of birth (patrilocal). This also discounts the plausibility of a harem society, which would have resulted in amatrilocal society due to heightened male–male competition. Males did not seem to have ventured very far from the valley, which could either indicate small home ranges, or that they preferred dolomitic landscapes due to perhaps cave abundance or factors related to vegetation growth.[75]
Dental development seems to have followed about the same timeframe as it does in modern humans and most other hominins, but, sinceParanthropus molars are markedly larger, rate oftooth eruption would have been accelerated.[12][78] Their life history may have mirrored that of gorillas as they have the same brain volume,[79] which (depending on the subspecies) reach physical maturity from 12–18 years and have birthing intervals of 40–70 months.[80]
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It is generally thought thatParanthropus preferred to inhabit wooded, riverine landscapes.[68] The teeth ofParanthropus,H. habilis andH. erectus are all known from various overlapping beds in East Africa, such as at Olduvai Gorge[81] and theTurkana Basin.[50]P. robustus andH. erectus also appear to have coexisted.[56][73]
P. boisei, known from the Great Rift Valley, may have typically inhabited wetlands along lakes and rivers, wooded or aridshrublands, and semiarid woodlands,[68] though their presence in the savanna-dominated MalawianChiwondo Beds implies they could tolerate a range of habitats.[82] During the Pleistocene, there seem to have been coastal and montane forests in Eastern Africa. More expansive river valleys—namely theOmo River Valley—may have served as important refuges for forest-dwelling creatures. Being cut off from the forests of Central Africa by a savanna corridor, these East African forests would have promoted high rates ofendemism, especially during times of climatic volatility.[83]
The Cradle of Humankind, the only areaP. robustus is known from, was mainly dominated by thespringbokAntidorcas recki, but other antelope,giraffes andelephants were also seemingly abundant megafauna. Other known primates are earlyHomo, thehamadryas baboon, and the extinctcolobine monkeyCercopithecoides williamsi.[84]
The left foot of aP. boisei specimen (though perhaps actually belonging toH. habilis) from Olduvai Gorge seems to have been bitten off by a crocodile,[85] possiblyCrocodylus anthropophagus,[86] and another's leg shows evidence of leopard predation.[85] Other likely Olduvan predators of great apes include thehunting hyenaChasmaporthetes nitidula, and thesabertoothed catsDinofelis andMegantereon.[64] The carnivore assemblage at the Cradle of Humankind comprises the two sabertooths, and the hyenaLycyaenops silberbergi.[84]
MaleP. robustus appear to have had a higher mortality rate than females. It is possible that males were more likely to be kicked out of a group, and these lone males had a higher risk of predation.[76]
It was once thought thatParanthropus had become a specialist feeder, and were inferior to the more adaptable tool-producingHomo, leading to their extinction, but this has been called into question.[36][64][65][67][71] However, smaller brain size may have been a factor in their extinction along with gracile australopithecines.[47]P. boisei may have died out due to an arid trend starting 1.45 mya, causing the retreat of woodlands, and more competition with savanna baboons andHomo for alternative food resources.[69]
South AfricanParanthropus appear to have outlasted their East African counterparts.[31] The youngest record ofP. boisei comes fromKonso, Ethiopia about 1.4 mya; however, there are no East African sites dated between 1.4 and 1 mya, so it may have persisted until 1 mya.[12]P. robustus, on the other hand, was recorded inSwartkrans until Member 3 dated to 1–0.6 mya (theMiddle Pleistocene), though more likely the younger side of the estimate.[31]
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