Paranthropus

It is debated whether the wide range of variation in jaw size indicates simply

groundmass filling in cracks naturally formed after death, inflating the perceived size of the bone.^[9][10][11] P. boisei also has a notably wide range of variation in skull anatomy, but these features likely have no taxonomic bearing.^[12]

P. aethiopicus

In 1968, French palaeontologists

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.^[14] Ferguson's classification is almost universally ignored,^[17] and is considered to be synonymous with P. aethiopicus.^[18]

Others

In 2015, Ethiopian palaeoanthropologist

There is currently no clear consensus on the validity of Paranthropus. The argument rests upon whether the genus is

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.^[10] It is possible that P. aethiopicus evolved even earlier, up to 3.3 mya, on the expansive Kenyan floodplains of the time.^[25] The oldest P. boisei remains date to about 2.3 mya from Malema, Malawi.^[10] P. boisei changed remarkably little over its nearly one-million-year existence.^[26] Paranthropus had spread into South Africa by 2 mya with the earliest P. robustus remains.^[16][27][28]

It is sometimes suggested that Paranthropus and Homo are

Paranthropus had adaptations to the skull to resist large bite loads while feeding, namely the expansive squamosal sutures.^[40] 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.^[41]

In P. boisei, the

The braincase volume averaged about 500 cm³ (31 cu in), comparable to gracile australopithecines, but smaller than Homo.[43] Modern human brain volume averages 1,270 cm³ (78 cu in) for men and 1,130 cm³ (69 cu in) for women.^[44]

Limbs and locomotion

Unlike P. robustus, the forearms of P. boisei were heavily built, which might suggest habitual

In comparison to the large, robust head, the body was rather small. Average weight for P. robustus may have been 40 kg (88 lb) for males and 32 kg (71 lb) for females;[16] and for P. boisei 50 kg (110 lb) for males and 34 kg (75 lb) for females.^[16] At Swartkrans Cave Members 1 and 2, about 35% of the P. 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).^[33] Female weight was about the same in contemporaneous H. erectus, but male H. erectus were on average 13 kg (28.7 lb) heavier than P. robustus males.^[52] 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.^[53] The largest-known Paranthropus individual was estimated at 54 kg (119 lb).^[33]

According to a 1991 study, based on femur length and using the dimensions of modern humans, male and female P. robustus are estimated to have stood on average 132 and 110 cm (4 ft 4 in and 3 ft 7 in), respectively, and P. 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 male P. boisei femurs at the time.^[34] In 2013, a 1.34 Ma male P. boisei partial skeleton was estimated to be at least 156 cm (5 ft 1 in) and 50 kg (110 lb).^[45]

Pathology

Paranthropus seems to have had notably high rates of

It was once thought P. 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.[56] In P. boisei, thick enamel was more likely used to resist abrasive gritty particles rather than to minimize chipping while eating hard foods.^[57] In fact, there is a distinct lack of tooth fractures which would have resulted from such activity.^[58][59]

Paranthropus were generalist feeders, but diet seems to have ranged dramatically with location. The South African P. robustus appears to have been an omnivore, with a diet similar to contemporaneous Homo

Juvenile P. robustus may have relied more on tubers than adults, given the elevated levels of strontium 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 the cementum and enamel 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.^[37]

Technology

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.[66]

Bone tools dating between 2.3 and 0.6 mya have been found in abundance in Swartkrans,

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 Age Homo.[27]

Bone tools may have been used to cut or process vegetation,^[67] or dig up tubers or termites,^[27][63] The form of P. robustus incisors appear to be intermediate between H. erectus and modern humans, which could indicate less food processing done by the teeth due to preparation with simple tools.^[37]

Burnt bones were also associated with the inhabitants of Swartkrans, which could indicate some of the earliest fire usage.^[68] However, these bones were found in Member 3, where Paranthropus remains are rarer than H. 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.^[69][70]

Social structure

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.^[71][72]

Paranthropus had pronounced

Dental development seems to have followed about the same timeframe as it does in modern humans and most other hominins, but, since Paranthropus molars are markedly larger, rate of tooth eruption would have been accelerated.^[11][74] Their life history may have mirrored that of gorillas as they have the same brain volume,^[75] which (depending on the subspecies) reach physical maturity from 12–18 years and have birthing intervals of 40–70 months.^[76]

Palaeoecology

Habitat

It is generally thought that Paranthropus preferred to inhabit wooded, riverine landscapes.

P. boisei, known from the Great Rift Valley, may have typically inhabited wetlands along lakes and rivers, wooded or arid shrublands, and semiarid woodlands,^[64] though their presence in the savanna-dominated Malawian Chiwondo Beds implies they could tolerate a range of habitats.^[78] During the Pleistocene, there seem to have been coastal and montane forests in Eastern Africa. More expansive river valleys—namely the Omo 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 of endemism, especially during times of climatic volatility.^[79]

The Cradle of Humankind, the only area P. robustus is known from, was mainly dominated by the

Male P. 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.[72]

Extinction

It was once thought that Paranthropus had become a specialist feeder, and were inferior to the more adaptable tool-producing Homo, leading to their extinction, but this has been called into question.^{[32][60][61][63][67]} However, smaller brain size may have been a factor in their extinction along with gracile australopithecines.^[43] 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 and Homo for alternative food resources.^[65]

South African Paranthropus appear to have outlasted their East African counterparts.

References

Further reading

• Grine, F. E. (2007). Evolutionary History of the Robust Australopithecines. Transaction Publishers.
  ISBN 978-0-202-36596-1
  .
• Wood, Bernard; Williams, Alexis (2020). "Meet Your Exotic, Extinct Close Relative: For a million years our likely ancestors in eastern Africa lived alongside creatures so peculiar that scientists today still struggle to make sense of them". American Scientist. 108 (6): 348.
  S2CID 241348079
  .

External links

Look up paranthropus in Wiktionary, the free dictionary.

Wikispecies has information related to Paranthropus.

Wikimedia Commons has media related to Paranthropus.

Wikibooks has a book on the topic of: Introduction to Paleoanthropology

• Reconstructions of P. boisei by John Gurche
• "Early Human Phylogeny". Smithsonian Institution. Archived from the original on 2005-11-02. Retrieved 2006-09-14.
• Human Timeline (Interactive) – Smithsonian, National Museum of Natural History (August 2016).