View source for Paranthropus boisei

{{short description|Extinct species of hominin of East Africa}}
{{good article}}
{{Speciesbox
| fossil_range = [[Early Pleistocene]], {{fossilrange|2.5|1.15}}
| image = Australophithecus boisei (cast), Olduvai Gorge - Springfield Science Museum - Springfield, MA - DSC03368.JPG
| image_caption = Reconstruction of the [[holotype specimen]] [[OH 5]]
| genus = Paranthropus
| species = boisei
| authority = ([[Louis Leakey]], 1959)
| synonyms = *''Zinjanthropus boisei''
*''Australopithecus boisei''
*''[[P. aethiopicus]]''?
}}

'''''Paranthropus boisei''''' is a [[species]] of [[australopithecine]] from the [[Early Pleistocene]] of East Africa about 2.5 to 1.15 million years ago.<ref>{{Cite web|last1=Wood|first1=Bernard|last2=Doherty|first2=Dandy|last3=Boyle|first3=Eve|date=2020-05-29|title=Hominin Taxic Diversity|url=https://oxfordre.com/anthropology/view/10.1093/acrefore/9780190854584.001.0001/acrefore-9780190854584-e-194|access-date=2021-04-19|website=Oxford Research Encyclopedia of Anthropology|language=en|doi=10.1093/acrefore/9780190854584.013.194|isbn=9780190854584}}</ref> The [[holotype specimen]], '''OH 5''', was discovered by palaeoanthropologist [[Mary Leakey]] in 1959 at Olduvai Gorge, Tanzania and [[species description|described]] by her husband [[Louis Leakey|Louis]] a month later. It was originally placed into its own [[genus]] as "'''''Zinjanthropus boisei'''''", but is now relegated to ''[[Paranthropus]]'' along with other robust australopithecines. However, it is also argued that ''Paranthropus'' is an invalid grouping and [[synonym (taxonomy)|synonymous]] with ''[[Australopithecus]]'', so the species is also often classified as '''''Australopithecus boisei'''''.

Robust australopithecines are characterised by heavily built skulls capable of producing high [[stress (physics)|stresses]] and [[bite force]]s, and some of the largest [[molar (tooth)|molars]] with the thickest [[tooth enamel|enamel]] of any known ape. ''P. boisei'' is the most robust of this group. Brain size was about {{cvt|450–550|cc}}, similar to other australopithecines. Some skulls are markedly smaller than others, which is taken as evidence of [[sexual dimorphism]] where females are much smaller than males, though body size is difficult to estimate given only one specimen, OH 80, definitely provides any bodily elements. The presumed male OH 80 may have been {{cvt|156|cm|ftin}} tall and {{cvt|61.7|kg}} in weight, and the presumed female KNM-ER 1500 {{cvt|124|cm|ftin}} tall (though its species designation is unclear). The arm and hand bones of OH 80 and KNM-ER 47000 suggest ''P. boisei'' was [[arboreal]] to a degree.

''P. boisei'' was originally believed to have been a [[generalist and specialist species|specialist species]] of hard foods, such as nuts, due to its heavily built skull, but it was more likely a generalist feeder of predominantly abrasive [[C4 carbon fixation#Plants that use C4 carbon fixation|C4]] plants, such as grasses or underground [[storage organ]]s. Like [[gorilla]]s, the apparently specialised adaptations of the skull may have only been used with less desirable fallback foods, allowing ''P. boisei'' to inhabit a wider range of habitats than gracile australopithecines. ''P. boisei'' may have been able to make [[Oldowan]] [[stone tool]]s and butcher carcasses. ''P. boisei'' mainly inhabited wet, wooded environments, and coexisted with ''[[H. habilis]]'', ''[[H. rudolfensis]]'' and ''[[H. ergaster]]''/''erectus''. These were likely preyed upon by the large carnivores of the time, including [[big cat]]s, [[crocodile]]s and [[hyena]]s.

==Research history==
{{redirect|OH 5|the Ohio congressional district|OH-5}}
[[File:Paranthropus Africa.jpg|thumb|left|Map of ''[[Paranthropus]]'' finds (''P. boisei'' in red)]]

===Discovery===
Palaeoanthropologists [[Mary Leakey|Mary]] and [[Louis Leakey|Louis]] Leakey had conducted excavations in Tanzania since the 1930s, though work was postponed with the start of [[World War II]]. They returned in 1951, finding mostly ancient tools and [[fossil]]s of extinct [[mammal]]s for the next few years.<ref>Mary Leakey, ''My Search'', 52–53, 83; Lewin & Foley, 234.</ref> In 1955, they unearthed a [[hominin]] [[deciduous tooth|baby]] [[canine tooth|canine]] and large [[molar tooth]] in [[Olduvai Gorge]], catalogue ID Olduvai Hominin (OH) 3.<ref name=Tobias2006>{{cite book|first=P. V.|last=Tobias|chapter=''Homo habilis''—A Premature Discovery: Remembered by One of Its Founding Fathers, 42 Years Later |author-link=Phillip V. Tobias|title=The First Humans – Origin and Early Evolution of the Genus ''Homo''|series=Vertebrate Paleobiology and Paleoanthropology|date=2009 |publisher=Springer, Dordrecht|pages=7–15|isbn=978-1-4020-9980-9|doi=10.1007/978-1-4020-9980-9_2}}</ref>

On the morning of July 17, 1959, Louis felt ill and stayed at camp while Mary went out to Bed I's [[Frida Leakey]] Gully.<ref>Bowman-Kruhm, 66; Mary Leakey, ''Excavations'', 227; Morell, 180–181.</ref> Sometime around 11:00&nbsp;AM, she noticed what appeared to be a portion of a skull poking out of the ground, OH 5.<ref>Mary Leakey, ''My Search'', 75.</ref> The dig team created a pile of stones around the exposed portion to protect it from further weathering.<ref name="excavations 227">Mary Leakey, ''Excavations'', 227.</ref> Active excavation began the following day; they had chosen to wait for photographer Des Bartlett to document the entire process.<ref name="excavations 227"/> The partial cranium was fully unearthed August 6, though it had to be reconstructed from its fragments which were scattered in the [[scree]].<ref>Cela-Conde & Ayala, 158; Morell, 183–184.</ref> Louis published a short summary of the find and context the following week.<ref>Louis Leakey, "A new fossil skull from Olduvai", 491–493.</ref>

Louis determined OH 5 to be a subadult or adolescent based on dental development, and he and Mary nicknamed it "Dear Boy".<ref>Cracraft & Donoghue, 524; Deacon, 56; Morell, 183–184.</ref> After they reconstructed the skull and jaws, newspapers began referring to it as "Nutcracker Man" due to the large back teeth and jaws which gave it a resemblance to vintage [[nutcracker doll|nutcrackers]].<ref>Cachel, 48.</ref> South African palaeoanthropologist [[Phillip Tobias]], a colleague of the Leakeys, has also received attribution for this nickname.<ref>Bowman-Kruhm, 66.</ref> The cranium was taken to Kenya after its discovery and was there until January 1965 when it was placed on display in the Hall of Man at the [[National Museum of Tanzania]] in Dar es Salaam.<ref name="staniforth 155">Staniforth, 155.</ref>

===Other specimens===
Louis preliminarily supposed OH 5 was about half a million years old, but in 1965, American geologists [[Garniss Curtis]] and Jack Evernden dated OH 5 to 1.75 million years ago using [[potassium–argon dating]] of [[Anorthoclase|anortoclase]] crystals from an overlying [[tuff]] (volcanic ash) bed.<ref>{{Cite journal|last1=Evernden|first1=J. F.|last2=Curtis|first2=G. H.|year=1965|title=The Potassium-Argon Dating of Late Cenozoic Rocks in East Africa and Italy [and Comments and Reply]|url=https://www.journals.uchicago.edu/doi/abs/10.1086/200619|journal=Current Anthropology|volume=6|issue=4|pages=342–385|doi=10.1086/200619|s2cid=143456420|issn=0011-3204}}</ref> Such an application of [[geochronology]] was unprecedented at the time.<ref>{{cite journal|first=W. H.|last=Gilbert|year=2013|title=Garniss Curtis (1919–2012): Dating Our Past|journal=PLOS Biology|volume=11|issue=9|page=e1001650|doi=10.1371/journal.pbio.1001650|pmc=3769222 |doi-access=free }}</ref>

[[File:Paranthropus y Australopithecus.jpg|thumb|Various ''P. boisei'' specimens]]
The first identified jawbone, [[Peninj 1]], was discovered [[Lake Natron]] just north of Olduvai Gorge in 1964.<ref name=wood2/>{{rp|107}}<ref>{{cite book|title=Journal of Eastern African Research and Development|url=https://books.google.com/books?id=B7BAAAAAYAAJ|year=1974|publisher=East African Literature Bureau|page=129|quote=The mandible was discovered by Kamoya Kimeu in 1964, during an expedition conducted by Richard Leakey and Glynn Isaac.}}</ref><ref name="Morell2011">{{cite book|author=Virginia Morell|title=Ancestral Passions: The Leakey Family and the Quest for Humankind's Beginnings|url=https://books.google.com/books?id=TKatWz1z3r8C&pg=PA303|date=11 January 2011|publisher=Simon and Schuster|isbn=978-1-4391-4387-2|page=303}}</ref> Especially from 1966 to 1975, several more specimens revealing facial elements were reported from the [[Shungura Formation]], Ethiopia; [[Koobi Fora]] and [[Chesowanja]], Kenya; and [[Omo Kibish Formation|Omo]] and [[Konso]], Ethiopia. Among the notable specimens found include the well preserved skull [[KNM-ER 406]] from Koobi Fora in 1970.<ref name=wood2/>{{rp|108–109}} In 1997, the first specimen with both the skull and jawbone (and also one of the largest specimens), KGA10-525, was discovered in Konso.<ref name=Suwa1997>{{cite journal|first1=G.|last1=Suwa|author1-link=Gen Suwa|first2=B.|last2=Asfaw|author2-link=Berhane Asfaw|first3=Y.|last3=Beyene|first4=T. D.|last4=White|author4-link=Tim D. White|display-authors=et al.|year=1997|title=The first skull of ''Australopithecus boisei''|journal=Nature|volume=389|issue=6650|pages=489–492|doi=10.1038/39037|pmid=9333236|bibcode=1997Natur.389..489S|s2cid=205026898}}</ref> In 1999, a jawbone was recovered from Malema<!--not Malema, Mozambique-->, Malawi, extending the species' southernmost range over {{cvt|2000|km}} from Olduvai Gorge.<ref name=wood2/>{{rp|109}} The first definitive bodily elements of ''P. boisei'' associated with facial elements, OH 80 (isolated teeth with an arm and a leg), were discovered in 2013. Previously, body remains lacking unambiguous diagnostic skull elements had been dubiously assigned to the species, namely the partial skeleton KNM-ER 1500 associated with a small jawbone fragment.<ref name=Dominguez2013>{{cite journal|first1=M.|last1=Domínguez-Rodrigo|first2=T. R.|last2=Pickering|first3=E.|last3=Baquedano|display-authors=et al.|year=2013|title=First Partial Skeleton of a 1.34-Million-Year-Old ''Paranthropus boisei'' from Bed II, Olduvai Gorge, Tanzania|journal=PLOS ONE|volume=8|issue=12|page=e80347|doi=10.1371/journal.pone.0080347|pmid=24339873|pmc=3855051|bibcode=2013PLoSO...880347D|doi-access=free}}</ref> In 2015, based on OH 80, American palaeoanthropologist Michael Lague recommended assigning the isolated humerus specimens KNM-ER 739, 1504, 6020 and 1591 from Koobi Fora to ''P. boisei''.<ref>{{cite journal|first=M. R.|last=Lague|year=2015|title=Taxonomic identification of Lower Pleistocene fossil hominins based on distal humeral diaphyseal cross-sectional shape|journal=PeerJ|volume=3|page=e1084|doi=10.7717/peerj.1084|pmc=4512774|pmid=26213653 |doi-access=free }}</ref> In 2020, the first associated hand bones were reported, KNM-ER 47000 (which also includes a nearly complete arm), from [[Ileret]], Kenya.<ref name=Richmond2020>{{cite journal|first1=B. G.|last1=Richmond|first2=D. J.|last2=Green|first3=M. R.|last3=Lague|display-authors=et al.|year=2020|title=The upper limb of ''Paranthropus boisei'' from Ileret, Kenya|journal=Journal of Human Evolution|volume=141|page=102727|doi=10.1016/j.jhevol.2019.102727|pmid=32078931|s2cid=211233056}}</ref>

===Naming===
The remains were clearly [[australopithecine]] (not of the genus ''[[Homo]]''), and at the time, the only australopithecine genera described were ''[[Australopithecus]]'' by [[Raymond Dart]] and ''[[Paranthropus]]'' (the South African ''[[Paranthropus robustus|P. robustus]]'') by [[Robert Broom]], and there were arguments that ''Paranthropus'' was [[synonym (taxonomy)|synonymous]] with ''Australopithecus''. Louis believed the skull had a mix of traits from both genera, briefly listing 20 differences, and so used OH 5 as the basis for the new genus and species "''Zinjanthropus boisei''" on August 15, 1959. The genus name derives from the medieval term for East Africa, "[[Zanj]]", and the specific name was in honour of [[Charles Watson Boise]], the Leakeys' benefactor.<ref name=Leakey1959>{{cite journal|first=L. S. B.|last=Leakey|author-link=Louis Leakey|year=1959|title=A new fossil skull from Olduvai|journal=Nature|volume=185|issue=4685|page=491|doi=10.1038/184491a0|bibcode=1959Natur.184..491L|s2cid=4217460}}</ref> He initially considered the name "''Titanohomo mirabilis''" ("wonderful Titan-like man").<ref>Johanson, Edgar & Brill, 156; Morell, 183.</ref>

Soon after, Louis presented "''Z.''" ''boisei'' to the 4th Pan-African Congress on Prehistory in Léopoldville, [[Belgian Congo]] (now [[Kinshasa]], Democratic Republic of the Congo).<ref name=Tobias2006/> Dart made his now famous joke, "... what would have happened if [the ''A. africanus'' specimen] [[Mrs. Ples]] had met Dear Boy one dark night." At the time of discovery, there was resistance to erecting completely new genera based on single specimens, and the Congress largely rejected "''Zinjanthropus''".<ref>Morell, Virginia. "Ancestral Passions: The Leakey Family and the Quest for Humankind's Beginnings". Touchstone, 2011. p. 193</ref> In 1960, American anthropologist [[John Talbot Robinson]] pointed out that the supposed differences between "''Zinjanthropus''" and ''Paranthropus'' are due to OH 5 being slightly larger, and so recommended the species be reclassified as ''P. boisei''. Louis rejected Robinson's proposal.<ref>{{cite journal|first=J. T.|last=Robinson|author-link=John Talbot Robinson|year=1960|title=The affinities of the new Olduvai australopithecines|journal=Nature|volume=186|issue=4723|pages=456–458|doi=10.1038/186456a0|bibcode=1960Natur.186..456R|s2cid=42964741}}</ref> Following this, it was debated if ''P. boisei'' was simply an East African variant of ''P. robustus'' until 1967 when South African palaeoanthropologist [[Phillip V. Tobias]] gave a far more detailed description of OH 5 in a [[monograph]] (edited by Louis). Tobias and Louis still retained "''Zinjanthropus''", but recommended demoting it to [[subgenus]] level as ''Australopithecus ("Zinjanthropus") boisei'', considering ''Paranthropus'' to be synonymous with ''Australopithecus''.<ref name=Tobias2006/> Synonymising ''Paranthropus'' with ''Australopithecus'' was first suggested by anthropologists [[Sherwood Washburn]] and Bruce D. Patterson in 1951, who recommended limiting hominin genera to only ''Australopithecus'' and ''Homo''.<ref>{{cite journal|first1=S. L.|last1=Washburn|author-link=Sherwood Washburn|first2=B.|last2=Patterson|year=1951|title=Evolutionary Importance of the South African 'Man-apes'|journal=Nature|volume=167|issue=4251|pages=650–651|doi=10.1038/167650a0|pmid=14826894|bibcode=1951Natur.167..650W|s2cid=4207075}}</ref>

==Classification==
{{Human timeline}}
The genus ''Paranthropus'' (otherwise known as "robust australopithecines") typically includes ''P. boisei'', ''P. aethiopicus'' and ''P. robustus''. It is debated if ''Paranthropus'' is a valid natural grouping ([[monophyletic]]) or an invalid grouping of similar-looking hominins ([[paraphyletic]]). Because skeletal elements are so limited in these species, their [[affinity (taxonomy)|affinities]] with each other and to other australopithecines is difficult to gauge with accuracy. The jaws are the main argument for monophyly, but such anatomy is strongly influenced by diet and environment, and could in all likelihood have evolved independently in ''P. boisei'' and ''P. robustus''. Proponents of monophyly consider ''P. aethiopicus'' to be ancestral to the other two species, or closely related to the ancestor. Proponents of paraphyly allocate these three species to the genus ''Australopithecus'' as ''A. boisei'', ''A. aethiopicus'' and ''A. robustus''.<ref name=wood2/>{{rp|117–121}}

Before ''P. boisei'' was described (and ''P. robustus'' was the only member of ''Paranthropus''), Broom and Robinson continued arguing that ''P. robustus'' and ''A. africanus'' (the then only known australopithecines) were two distinct lineages. However, remains were not firmly dated, and it was debated if there were indeed multiple hominin lineages or if there was only 1 leading to humans. In 1975, the ''P. boisei'' skull KNM-ER 406 was demonstrated to have been contemporaneous with the ''[[H. ergaster]]''/''erectus'' skull [[KNM ER 3733]], which is generally taken to show that ''Paranthropus'' was a [[sister taxon]] to ''Homo'', both developing from some ''Australopithecus'' species, which at the time only included ''A. africanus''. In 1979, a year after describing ''[[A. afarensis]]'' from East Africa, anthropologists [[Donald Johanson]] and [[Tim D. White]] suggested that ''A. afarensis'' was instead the last common ancestor between ''Homo'' and ''Paranthropus'', and ''A. africanus'' was the earliest member of the ''Paranthropus'' lineage or at least was ancestral to ''P. robustus'', because ''A. africanus'' inhabited South Africa before ''P. robustus'', and ''A. afarensis'' was at the time the oldest-known hominin species at roughly 3.5 million years old.<ref>{{cite journal|first1=D. C.|last1=Johanson|author-link=Donald Johanson|first2=T. D.|last2=White|author2-link=Tim D. White|year=1979|title=A Systematic Assessment of Early African Hominids|journal=Science|volume=203|issue=4378|pages=321–330|doi=10.1126/science.104384|pmid=104384|bibcode=1979Sci...203..321J}}</ref> Now, the earliest known South African australopithecine ("[[Little Foot]]") dates to 3.67 million years ago, contemporaneous with ''A. afarensis''.<ref>{{cite journal|first1=R. J.|last1=Clarke|author-link=Ronald J. Clarke|first2=K.|last2=Kuman|year=2019|title=The skull of StW 573, a 3.67 Ma ''Australopithecus prometheus'' skeleton from Sterkfontein Caves, South Africa|journal=Journal of Human Evolution|volume=134|page=102634|doi=10.1016/j.jhevol.2019.06.005|pmid=31446970|s2cid=201209318}}</ref>

Such arguments are based on how one draws the hominin family tree, and the exact classification of ''Australopithecus'' species with each other is quite contentious. For example, if the South African ''[[A. sediba]]'' (which evolved from ''A. africanus'') is considered the ancestor or closely related to the ancestor of ''Homo'', then this could allow for ''A. africanus'' to be placed more closely related to ''Homo'' than to ''Paranthropus''. This would leave the Ethiopian ''[[A. garhi]]'' as the ancestor of ''P. aethiopicus'' instead of ''A. africanus'' (assuming ''Paranthropus'' is monophyletic, and that ''P. aethiopicus'' evolved at a time in East Africa when only ''A. garhi'' existed there).<ref name=McNulty2016>{{cite journal|first=K. P.|last=McNulty|year=2016|title=Hominin Taxonomy and Phylogeny: What's In A Name?|journal=Nature Education Knowledge|volume=7|issue=1|page=2|url=https://www.nature.com/scitable/knowledge/library/hominin-taxonomy-and-phylogeny-what-s-in-142102877/}}</ref>

{{clade gallery
|align=left |height=225px|main-borders= 
|main-footer=Three example family trees with ''P. boisei'' (note, they are not absolute)
|caption1=Monophyly<ref name=wood2/>{{rp|119}}
|caption2=Paraphyly<ref name=wood2/>{{rp|119}}
|caption3=Monophyly<ref name=McNulty2016/>
|cladogram1=
{{clade
 |1={{clade
  |1=''[[Australopithecus africanus|A. africanus]]''
  |2={{clade
   |1=''[[P. aethiopicus]]''
   |2={{clade
    |1='''''P. boisei'''''
    |2=''[[Paranthropus robustus|P. robustus]]''
    }}
   }}
  }}
 }}
|cladogram2=
{{clade
 |1={{clade
  |1=''[[Australopithecus africanus|A. africanus]]''
  |2=''[[Paranthropus robustus|P. robustus]]''
  }}
 |2={{clade
  |1=''[[P. aethiopicus]]''
  |2='''''P. boisei'''''
  }}
 }}
|cladogram3=
{{clade
 |1={{clade
  |label1=''[[Australopithecus africanus|A. africanus]]''
  |1={{clade
   |1=''[[Homo]]''
   |2=''[[Australopithecus sediba]]''
   }}
  |2={{clade
   |1=''[[A. garhi]]''
   |label2=''[[P. aethiopicus]]''
   |2={{clade
    |1='''''P. boisei'''''
    |2=''[[Paranthropus robustus|P. robustus]]''
   }}
  }}
}}}}
}}
{{-}}
Because ''P. boisei'' and ''P. aethiopicus'' are both known from East Africa and ''P. aethiopicus'' is only confidently identified from the skull [[KNM WT 17000]] and a few jaws and isolated teeth, it is debated if ''P. aethiopicus'' should be subsumed under ''P. boisei'' or if the differences stemming from archaicness justifies species distinction. The terms ''P. boisei'' [[sensu lato]] ("in the broad sense") and ''P. boisei'' [[sensu stricto]] ("in the strict sense") can be used to respectively include and exclude ''P. aethiopicus'' from ''P. boisei'' when discussing the lineage as a whole.<ref name=wood2/>{{rp|106–107}}

{{African hominin timeline}}

''P. aethiopicus'' is the earliest member of the genus, with the oldest remains, from the Ethiopian [[Omo Kibish Formation]], dated to 2.6 million years ago (mya) at the end of the [[Pliocene]].<ref name=Constantino2007/> It is possible that ''P. aethiopicus'' evolved even earlier, up to 3.3 mya, on the expansive Kenyan floodplains of the time.<ref name=Joordens2019>{{cite journal|first1=J. C. A.|last1=Joordens|first2=C. S.|last2=Feibel|first3=H. B.|last3=Vonhof|first4=A. S.|last4=Schulp|first5=D.|last5=Kroon|year=2019|title=Relevance of the eastern African coastal forest for early hominin biogeography|journal=Journal of Human Evolution|volume=131|pages=176–202|pmid=31182201|doi=10.1016/j.jhevol.2019.03.012|doi-access=free|hdl=20.500.11820/6c1ee960-79ba-45df-9e12-3350c768a497|hdl-access=free}}</ref> The oldest ''P. boisei'' remains date to about 2.3 mya from Malema.<ref name=Constantino2007>{{cite journal|first1=P. J.|last1=Constantino|first2=B. A.|last2=Wood|year=2007|title=The Evolution of ''Zinjanthropus boisei''|journal=Evolutionary Anthropology|volume=16|issue=2|pages=49–62|doi=10.1002/evan.20130|s2cid=53574805|url=https://mds.marshall.edu/cgi/viewcontent.cgi?article=1027&context=bio_sciences_faculty}}</ref> The youngest record of ''P. boisei'' comes Olduvai Gorge (OH 80) about 1.34 mya;<ref name=Dominguez2013/> however, due a large gap in the hominin fossil record, ''P. boisei'' may have persisted until 1 mya.<ref name=wood2/>{{rp|109}} ''P. boisei'' changed remarkably little over its nearly one-million-year existence.<ref>{{cite journal|first1=B.|last1=Wood|first2=C.|last2=Wood|first3=L.|last3=Konigsberg|year=1994|title=''Paranthropus boisei'': an example of evolutionary stasis?|journal=American Journal of Physical Anthropology|volume=95|issue=2|pages=117–136|doi=10.1002/ajpa.1330950202|pmid=7802091}}</ref>

==Anatomy==
===Skull===
[[File:Paranthropus boisei - forensic facial reconstruction.png|thumb|Reconstruction of ''P. boisei'' by Cicero Moraes]]
''P. boisei'' is the most robust of the robust australopithecines, whereas the South African ''P. robustus'' is smaller with comparatively more gracile features.<ref name=wood2/>{{rp|120}} The ''P. boisei'' skull is heavily built, and features a defined [[brow ridge]], receding forehead, rounded bottom margins of the [[orbit (anatomy)|eye sockets]], inflated and concave [[cheek bone]]s, a thick [[palate]], and a robust and deep jawbone. This is generally interpreted as having allowed ''P. boisei'' to resist high stresses while chewing,<ref name=Wood2004/> though the thick palate could instead be a byproduct of facial lengthening.<ref>{{cite journal|first=M. A.|last=McCollum|year=1998|title=Palatal thickening and facial form in ''Paranthropus'': Examination of alternative developmental models|journal=American Journal of Physical Anthropology|volume=103|issue=3|pages=375–392|doi=10.1002/(SICI)1096-8644(199707)103:3<375::AID-AJPA7>3.0.CO;2-P|pmid=9261500|doi-access=free}}</ref> The skull features large rough patches (rugosities) on the cheek and jawbones, and males have pronounced [[sagittal crest|sagittal]] (on the midline) and temporonuchal (on the back) crests, which indicate a massive [[masseter muscle]] (used in biting down) placed near the front of the head (increasing [[mechanical advantage]]). This is typically considered to be evidence of a high [[bite force]].<ref name=Wood2004/>

The [[incisor]]s and canines are reduced, which would hinder biting off chunks of large food pieces. In contrast, the [[cheek teeth]] of both sexes are enormous ([[postcanine megadontia]]), and the greater surface area would have permitted the processing of larger quantities of food at once.<ref name=Wood2004/> In the upper jaw, the 1st molar averages roughly {{cvt|250|mm2}}, the 2nd molar {{cvt|320|mm2}}, and the 3rd molar {{cvt|315|mm2}}; in the lower jaw, the 1st molar averages roughly {{cvt|260|mm2}}, the 2nd molar {{cvt|315|mm2}}, and the 3rd molar {{cvt|340|mm2}}.<ref>{{cite journal|first1=B. A.|last1=Wood|first2=L.|last2=Zuckerman|year=1981|title=Tooth Size and Shape and their Relevance to Studies of Hominid Evolution|journal=Philosophical Transactions of the Royal Society B|volume=292|issue=1057|page=71|jstor=2398644|doi=10.1098/rstb.1981.0014|pmid=6115408|bibcode=1981RSPTB.292...65W}}</ref> The molars are [[bunodont]], featuring low and rounded [[cusp (anatomy)|cusps]]. The [[premolar]]s resemble molars (are molarised), which may indicate ''P. boisei'' required an extended chewing surface for processing a lot of food at the same time. The [[tooth enamel|enamel]] on the cheek teeth are among the thickest of any known ape, which would help resist high stresses while biting.<ref name=Wood2004>{{cite journal|first1=B.|last1=Wood|first2=D.|last2=Strait|year=2004|title=Patterns of resource use in early ''Homo'' and ''Paranthropus''|journal=Journal of Human Evolution|volume=46|issue=2|pages=119–162|doi=10.1016/j.jhevol.2003.11.004|pmid=14871560}}</ref>{{rp|128–132}}
[[File:Australopithecus boisei Peninj 1 IMG 5626 BMNH.jpg|thumb|[[Peninj 1]] showing [[postcanine megadontia]]]]

===Brain and sinuses===
In a sample of 10 ''P. boisei'' specimens, brain size varied from {{cvt|444–545|cc}} with an average of {{cvt|487.5|cc}}.<ref>{{cite journal|first1=S.|last1=Elton|first2=L. C.|last2=Bishop|first3=B.|last3=Wood|year=2001|title=Comparative context of Plio-Pleistocene hominin brain evolution|journal=Journal of Human Evolution|volume=41|issue=1|page=16|doi=10.1006/jhev.2001.0475|pmid=11414771}}</ref> However, the lower-end specimen, Omo L338‐y6, is a juvenile, and many skull specimens have a highly damaged or missing [[frontal bone]] which can alter brain volume estimates.<ref>{{cite journal|first=J.|last=Hawks|author-link=John D. Hawks|year=2011|title=No brain expansion in ''Australopithecus boisei''|journal=American Journal of Physical Anthropology|volume=146|issue=2|pages=155–160|doi=10.1002/ajpa.21420|pmid=21915845|doi-access=free}}</ref> The brain volume of australopithecines generally ranged from {{cvt|400–500|cc}}, and for contemporary ''Homo'' {{cvt|500–900|cc}}.<ref name=Tobias1987>{{cite journal|first=P. V.|last=Tobias|year=1987|title=The brain of ''Homo habilis'': A new level of organization in cerebral evolution|journal=Journal of Human Evolution|volume=16|issue=7–8|pages=741–761|doi=10.1016/0047-2484(87)90022-4}}</ref>

Regarding the [[dural venous sinuses]], in 1983, American neuroanthropologist [[Dean Falk]] and anthropologist Glenn Conroy suggested that, unlike ''A. africanus'' or modern humans, all ''Paranthropus'' (and ''A. afarensis'') had expanded [[occipital sinus|occipital]] and marginal (around the [[foramen magnum]]) sinuses, completely supplanting the [[transverse sinus|transverse]] and [[sigmoid sinus]]es. In 1988, Falk and Tobias demonstrated that hominins can have both an occipital/marginal and transverse/sigmoid systems concurrently or on opposite halves of the skull, such as with the ''P. boisei'' specimen KNM-ER 23000.<ref>{{cite book|first=H. M.|last=McHenry|author-link=Henry McHenry (anthropologist)|chapter=Enlarged occipital/marginal sinuses and emissary foramina: Their significance in hominid evolution|editor-first=F. E.|editor-last=Grine|title=Evolutionary History of the "Robust" Australopithecines|year=1988|pages=133–148|publisher=Routledge |isbn=978-1-351-52126-0}}</ref>
[[File:Paranthropus boisei model NMNH.jpg|thumb|''Paranthropus boisei'' facial reconstruction at the [[Smithsonian National Museum of Natural History]]]]
In 1983, French anthropologist Roger Saban stated that the parietal branch of the [[middle meningeal artery]] originated from the posterior branch in ''P. boisei'' and ''P. robustus'' instead of the anterior branch as in earlier hominins, and considered this a derived characteristic due to increased brain capacity.<ref>{{cite journal|first=R.|last=Saban|year=1983|title=Les veines méningées moyennes des Australopithèques|journal=Bulletins et Mémoires de la Société d'Anthropologie de Paris|language=fr|volume=13|issue=3|pages=313–323|doi=10.3406/bmsap.1983.3905|url=https://www.persee.fr/doc/bmsap_0037-8984_1983_num_10_3_3905}}</ref> It has since been demonstrated that the parietal branch could originate from either the anterior or posterior branches, sometimes both in a single specimen on opposite sides of the skull as in KNM-ER 23000 and OH 5.<ref>{{cite journal|first1=B.|last1=Brown|first2=A.|last2=Walker|author2-link=Alan Walker (anthropologist)|first3=C. V.|last3=Ward|first4=R. E.|last4=Leakey|author4-link=Richard Leakey|year=1993|title=New ''Australopithecus boisei'' calvaria from East Lake Turkana, Kenya|journal=American Journal of Physical Anthropology|volume=91|issue=2|page=157|doi=10.1002/ajpa.1330910202|pmid=8317557}}</ref>

===Postcranium===
The wide range of size variation in skull specimens seems to indicate a great degree of [[sexual dimorphism]] with males being notably bigger than females. However, it is difficult to predict with accuracy the true dimensions of living males and females due to the lack of definitive ''P. boisei'' skeletal remains, save for the presumed male OH 80. Based on an approximation of {{cvt|400|mm|ft}} for the [[femur]] before it was broken and using modern humanlike proportions (which is probably an unsafe assumption), OH 80 was about {{cvt|156.3|cm|ftin}} tall in life.<ref name=Dominguez2013/> For comparison, modern human men and women in the year 1900 averaged {{cvt|163|cm|ftin}} and {{cvt|152.7|cm|ft}}, respectively.<ref>{{cite journal|url=https://ourworldindata.org/human-height|first1=M.|last1=Roser|author1-link=Max Roser |first2=C.|last2=Appel|first3=H.|last3=Ritchie|author3-link=Hannah Ritchie |year=2013|title=Human Height|journal=Our World in Data|access-date=16 June 2020}}</ref> The [[epiphysis|femoral head]], the best proxy for estimating body mass, is missing, but using the shaft, OH 80 weighed about {{cvt|50|kg}} assuming humanlike proportions, and {{cvt|61.7|kg}} using the proportions of a non-human ape.<ref name=Dominguez2013/> The ambiguously attributed, presumed female femur KNM-ER 1500 is estimated to have been of an individual about {{cvt|124|cm|ftin}} tall<ref name=McHenry1991b>{{cite journal|first=H. M.|last=McHenry|author-link=Henry McHenry (anthropologist)|year=1991|title=Femoral lengths and stature in Plio-Pleistocene hominids|journal=American Journal of Physical Anthropology|volume=85|issue=2|pages=149–158|doi=10.1002/ajpa.1330850204|pmid=1882979}}</ref> which would be consistent with the argument of sexual dimorphism,<ref name=Dominguez2013/> but if the specimen does indeed belong to ''P. boisei'', it would show a limb anatomy quite similar to that of the contemporary ''[[H. habilis]]''.<ref name=wood2>{{cite journal |first1=Bernard |last1=Wood |first2=Paul |last2=Constantino |year=2007 |title=''Paranthropus boisei'': Fifty years of evidence and analysis |journal=American Journal of Physical Anthropology |volume=134|issue=Suppl 45 |pages=106–32 |pmid=18046746 |doi=10.1002/ajpa.20732|url=https://mds.marshall.edu/cgi/viewcontent.cgi?article=1035&context=bio_sciences_faculty |doi-access=free }}</ref>{{rp|116}}

[[File:OH 80 Paranthropus boisei Journal.pone.0080347.g002.png|thumb|upright=0.7|right|OH 80 [[femoral shaft]] (left) and [[Radius (bone)|radius]] (right)<br/>Scale bar={{cvt|1|cm}}]]
Instead, the OH 80 femur, more like ''[[Homo erectus|H. erectus]]'' femora, is quite thick, features a laterally flattened shaft, and indicates similarly arranged [[anterior gluteal line|gluteal]], [[pectineal line (femur)|pectineal]] and [[intertrochanteric line|intertrochanteric]] lines around the [[hip joint]]. Nonetheless, the intertrochanteric line is much more defined in OH 80, the [[gluteal tuberosity]] is more towards the midline of the femur, and the mid-shaft in side-view is straighter, which likely reflect some difference in load-bearing capabilities of the leg. Unlike ''P. robustus'', the arm bones of OH 80 are heavily built, and the [[elbow joint]] shows similarities to that of modern [[gibbon]]s and [[orangutan]]s. This could either indicate that ''P. boisei'' used a combination of terrestrial walking as well as [[suspensory behaviour]], or was completely bipedal but retained an ape-like upper body condition from some ancestor species due to a lack of selective pressure to lose them. In contrast, the ''P. robustus'' hand is not consistent with climbing.<ref name=Dominguez2013/> The hand of KNM-ER 47000 shows ''Australopithecus''-like anatomy lacking the [[third metacarpal styloid process]] (which allows the hand to lock into the wrist to exert more pressure), a weak thumb compared to modern humans, and curved [[phalanx bone|phalanges]] (finger bones) which are typically interpreted as adaptations for climbing. Nonetheless, despite lacking a particularly forceful [[precision grip]] like ''Homo'', the hand was still dextrous enough to handle and manufacture simple tools.<ref name=Richmond2020/>

==Palaeobiology==
===Diet===
In 1954, Robinson suggested that the heavily built skull of ''Paranthropus'' (at the time only including ''P. robustus'') was indicative of a [[generalist and specialist species|specialist]] diet specifically adapted for processing a narrow band of foods. Because of this, the predominant model of ''Paranthropus'' extinction for the latter half of the 20th century was that it was unable to adapt to the volatile climate of the [[Pleistocene]], unlike the much more adaptable ''Homo''.<ref name=Wood2004/> It was also once thought ''P. boisei'' cracked open nuts and similar hard foods with its powerful teeth, giving OH 5 the nickname "Nutcracker Man".<ref>{{cite journal|first1=P. S.|last1=Ungar|first2=F. E.|last2=Grine|first3=M. F.|last3=Teaford|year=2008|title=Dental Microwear and Diet of the Plio-Pleistocene Hominin ''Paranthropus boisei''|journal=PLOS ONE|volume=3|issue=4|page=e2044|doi=10.1371/journal.pone.0002044|pmc=2315797|pmid=18446200|bibcode=2008PLoSO...3.2044U|doi-access=free}}</ref>

However, in 1981, English anthropologist [[Alan Walker (anthropologist)|Alan Walker]] found that the microwearing patterns on the molars were inconsistent with a diet high in hard foods, and were effectively indistinguishable from the pattern seen in the molars of fruit-eating ([[frugivorous]]) [[mandrill]]s, [[chimpanzee]]s and [[orangutan]]s.<ref>{{cite journal|first=A.|last=Walker|author-link=Alan Walker (anthropologist)|year=1981|title=Diet and teeth: Dietary hypotheses and human evolution|journal=Philosophical Transactions of the Royal Society B|volume=292|issue=1057|pages=60–61|doi=10.1098/rstb.1981.0013|pmid=6115407|doi-access=}}</ref> The microwearing on ''P. boisei'' molars is different from that on ''P. robustus'' molars, and indicates that ''P. boisei'', unlike ''P. robustus'', very rarely ever ate hard foods. [[Isotope analysis#Carbon-13|Carbon isotope analyses]] report a diet of predominantly [[C4 carbon fixation#Plants that use C4 carbon fixation|C4]] plants, such as low quality and abrasive grasses and sedges.<ref name=pmid18446200>{{cite journal |first1=Peter S. |last1=Ungar |first2=Frederick E. |last2=Grine |first3=Mark F. |last3=Teaford |date=April 2008 |editor1-last=Petraglia |editor1-first=Michael |title=Dental Microwear and Diet of the Plio-Pleistocene Hominin ''Paranthropus boisei'' |journal=[[PLoS ONE]] |volume=3 |issue=4 |pages=e2044 |doi=10.1371/journal.pone.0002044 |pmid=18446200 |pmc=2315797 |bibcode=2008PLoSO...3.2044U|doi-access=free }}</ref><ref>{{cite journal |last1=Scott |first1=Robert S. |last2=Ungar |first2=Peter S. |last3=Bergstrom |first3=Torbjorn S. |last4=Brown |first4=Christopher A. |last5=Grine |first5=Frederick E. |last6=Teaford |first6=Mark F. |last7=Walker |first7=Alan |year=2005 |title=Dental microwear texture analysis shows within-species diet variability in fossil hominins |journal=Nature |volume=436 |issue=7051 |pages=693–5 |doi=10.1038/nature03822 |pmid=16079844 |bibcode=2005Natur.436..693S|s2cid=4431062 |url=http://doc.rero.ch/record/15300/files/PAL_E2599.pdf }}</ref><ref name=cerling>{{cite journal |first1=Thure E. |last1=Cerling |first2=Emma |last2=Mbua |first3=Francis M. |last3=Kirera |first4=Fredrick Kyalo |last4=Manthi |first5=Frederick E. |last5=Grine |first6=Meave G. |last6=Leakey |first7=Matt |last7=Sponheimer |first8=Kevin T. |last8=Unoa |year=2011 |title=Diet of ''Paranthropus boisei'' in the early Pleistocene of East Africa |journal=Proceedings of the National Academy of Sciences |volume=108 |issue=23 |pages=9337–41 |doi=10.1073/pnas.1104627108 |pmid=21536914 |bibcode=2011PNAS..108.9337C |pmc=3111323|doi-access=free }}</ref> Thick enamel is consistent with grinding abrasive foods.<ref name=Wood2004/> The microwear patterns in ''P. robustus'' have been thoroughly examined, and suggest that the heavy build of the skull was only relevant when eating less desirable fallback foods. A similar scheme may have been in use by ''P. boisei''.<ref name=Wood2004/> Such a strategy is similar to that used by modern [[gorilla]]s, which can sustain themselves entirely on lower quality fallback foods year-round, as opposed to lighter built chimps (and presumably gracile australopithecines) which require steady access to high quality foods.<ref name=Laden2005/>

[[File:Paranthropus boisei IMG 2932-white.jpg|thumb|upright|Reconstruction of MGL 95211 skull and jaw]]
In 1980, anthropologists Tom Hatley and John Kappelman suggested that early hominins ([[convergent evolution|convergently]] with [[bear]]s and [[pig]]s) adapted to eating abrasive and calorie-rich underground [[storage organ]]s (USOs), such as roots and tubers.<ref>{{cite journal|first1=T.|last1=Hatley|first2=J.|last2=Kappelman|year=1980|title=Bears, pigs, and Plio-Pleistocene hominids: A case for the exploitation of belowground food resources|journal=Human Ecology|volume=8|issue=4|pages=371–387|doi=10.1007/BF01561000|jstor=4602571|s2cid=86632664}}</ref> Since then, hominin exploitation of USOs has gained more support. In 2005, biological anthropologists [[Greg Laden]] and [[Richard Wrangham]] proposed that ''Paranthropus'' relied on USOs as a fallback or possibly primary food source, and noted that there may be a correlation between high USO abundance and hominin occupation.<ref name=Laden2005>{{cite journal|first1=G.|last1=Laden|author1-link=Greg Laden|first2=R.|last2=Wrangham|author2-link=Richard Wrangham|year=2005|title=The rise of the hominids as an adaptive shift in fallback foods: Plant underground storage organs (USOs) and australopith origins|journal=Journal of Human Evolution|volume=49|issue=4|pages=482–498|doi=10.1016/j.jhevol.2005.05.007|pmid=16085279}}</ref> In this model, ''P. boisei'' may have been a generalist feeder with a predilection for USOs,<ref>{{cite journal |last1=Griffith |first1=Cameron S. |last2=Long |first2=Byron L. |last3=Sept |first3=Jeanne M. |year=2010 |title=HOMINIDS: An agent-based spatial simulation model to evaluate behavioral patterns of early Pleistocene hominids |journal=Ecological Modelling |volume=221 |issue=5 |pages=738–60 |doi=10.1016/j.ecolmodel.2009.11.009}}</ref><ref name="cerling"/> and may have gone extinct due to an aridity trend and a resultant decline in USOs in tandem with increasing competition with [[baboon]]s and ''Homo''.<ref>{{cite journal |last1=Macho |first1=Gabriele A. |year=2014 |title=Baboon Feeding Ecology Informs the Dietary Niche of ''Paranthropus boisei'' |journal=PLOS ONE |volume=9 |issue=1 |pages=84942 |pmid=24416315 |pmc=3885648 |bibcode=2014PLoSO...984942M |doi=10.1371/journal.pone.0084942|doi-access=free }}</ref> Like modern chimps and baboons, australopithecines likely foraged for food in the cooler morning and evening instead of in the heat of the day.<ref name=David2016/>

===Technology===
By the time OH 5 was discovered, the Leakeys had spent 24 years excavating the area for early hominin remains, but had instead recovered mainly other animal remains as well as the [[Oldowan]] [[stone tool]] [[industry (archaeology)|industry]].<ref name=Tobias2006/> Because OH 5 was associated with the tools and processed animal bones, they presumed it was the toolmaker. Attribution of the tools was promptly switched to the bigger-brained ''H. habilis'' upon its description in 1964.<ref name=Tobias2006/> In 2013, OH 80 was found associated with a mass of Oldowan stone tools and animal bones bearing evidence of butchery. This could potentially indicate ''P. boisei'' was manufacturing this industry and ate meat to some degree.<ref name=Dominguez2013/>

Additionally, the [[Early Stone Age]] of Africa coincides with simple [[bone tool]]s. In South Africa, these are unearthed in the [[Cradle of Humankind]] and are largely attributed to ''P. robustus''. In East Africa, a few have been encountered at Olduvai Gorge Beds I–IV, occurring over roughly 1.7 to 0.8 million years ago, and are usually made of limb bones and possibly teeth of large mammals, most notably [[elephant]]s. The infrequency of such large animals at this site may explain the relative rarity of bone tools. The toolmakers were modifying bone in much the same way as they did with stone. Though the Olduvan bone tools are normally ascribed to ''H. ergaster''/''erectus'', the presence of both ''P. boisei'' and ''H. habilis'' obfuscates attribution.<ref>{{cite journal|last1=Pante|first1=M.|last2=de la Torre|first2=I.|last3=d’ Errico|first3=F.|last4=Njau|first4=J.|last5=Blumenschine|first5=R.|year=2020|title=Bone tools from Beds II–IV, Olduvai Gorge, Tanzania, and implications for the origins and evolution of bone technology|journal=Journal of Human Evolution|volume=148|page=102885|doi=10.1016/j.jhevol.2020.102885|pmid=33049586|s2cid=222351728|url=https://hal.archives-ouvertes.fr/hal-02998313/file/pagination_YJHEV_102885.pdf}}</ref>

===Social structure===
In 1979, American biological anthropologist [[Noel T. Boaz]] noticed that the relative proportions between large mammal families at the Shungura Formation are quite similar to the proportion in modern-day across sub-Saharan Africa. Boaz believed that hominins would have had about the same population density as other large mammals, which would equate to 0.006–1.7 individuals per square kilometre (0.4 square mile). Alternatively, by multiplying the density of either bovids, elephants, or hippos by the percentage of hominin remains out of total mammal remains found at the formation, Boaz estimated a density of 0.001–2.58 individuals per square kilometre.<ref>{{cite journal|first=N. T.|last=Boaz|author-link=Noel T. Boaz|year=1979|title=Early Hominid Population Densities: New Estimates|journal=Science|volume=206|issue=4418|pages=592–595|doi=10.1126/science.206.4418.592|pmid=17759430|bibcode=1979Sci...206..592B|s2cid=1531319}}</ref> Biologist Robert A. Martin considered population models based on the number of known specimens to be flimsy. In 1981, Martin applied equations formulated by ecologists Alton S. Harestad and Fred L. Bunnel in 1979 to estimate the home range and population density of large mammals based on weight and diet, and, using a weight of {{cvt|52.4|kg}}, he got: {{cvt|130|ha}} and 0.769 individual per square kilometre if herbivorous; {{cvt|1295|ha}} and 0.077 individual if omnivorous; and {{cvt|287819|ha}} and 0.0004 individual if carnivorous. For comparison, he calculated {{cvt|953|ha}} and 0.104 individual per square kilometre for omnivorous, {{convert|37.5|kg|adj=on}} chimps.<ref>{{cite journal|last=Martin|first=R. A.|year=1981|title=On extinct hominid population densities|journal=Journal of Human Evolution|volume=10|issue=5|pages=427–428|doi=10.1016/s0047-2484(81)80006-1}}</ref>

[[File:Gorilla gorilla skull.jpg|thumb|upright=1.3|Male (left) and female (right) [[western gorilla]] skulls]]
A 2017 study postulated that, because male non-human [[great ape]]s have a larger sagittal crest than females (particularly gorillas and orangutans), the crest may be influenced by [[sexual selection]] in addition to supporting chewing muscles. Further, the size of the sagittal crest (and the [[gluteus muscle]]s) in male [[western lowland gorilla]]s has been correlated with reproductive success. They extended their interpretation of the crest to the males of ''Paranthropus'' species, with the crest and resultantly larger head (at least in ''P. boisei'') being used for some kind of [[display (zoology)|display]]. This contrasts with other primates which flash the typically engorged canines in agonistic display (the canines of ''Paranthropus'' are comparatively small). However, it is also possible that male gorillas and orangutans require larger temporalis muscles to achieve a wider gape to better display the canines.<ref>{{cite journal|first1=K. L.|last1=Balolia|first2=C.|last2=Soligo|first3=B.|last3=Wood|year=2017|title=Sagittal crest formation in great apes and gibbons|journal=Journal of Anatomy|volume=230|issue=6|pages=820–832|doi=10.1111/joa.12609|pmid=28418109|pmc=5442144|doi-access=free}}</ref>

===Development===
Australopithecines are generally considered to have had a faster, [[ape]]like growth rate than modern [[human]]s largely due to dental development trends. Broadly speaking, the emergence of the first permanent molar in early hominins has been variously estimated anywhere from 2.5 to 4.5 years of age, which all contrast markedly with the modern human average of 5.8 years. The tips of the mesial cusps of the 1st molar (on the side closest to the premolar) of KNM-ER 1820 were at about the same level as the cervix (where the enamel meets the [[cementum]]) of its non-permanent 2nd premolar. In baboons, this stage occurs when the 1st molar is about to erupt from the gums. The [[tooth root]] is about {{cvt|5|mm}}, which is similar to most other hominins at this stage. In contrast, the root of the ''P. robustus'' specimen SK 62 was {{cvt|6|mm}} when emerging through the [[dental alveolus]] (an earlier stage of development than gum emergence), so, unless either specimen is abnormal, ''P. robustus'' may have had a higher tooth-root formation rate. The specimen's 1st molar may have erupted 2–3 months before death, so possibly at 2.7–3.3 years of age. In modern apes (including humans), dental development trajectory is strongly correlated with life history and overall growth rate, but it is possible that early hominins simply had a faster dental trajectory and slower life history due to environmental factors, such as early weaning age exhibited in modern [[Indriidae|indriid]] [[lemur]]s.<ref name=Kelley2012>{{cite journal|first1=J.|last1=Kelley|first2=G. T.|last2=Schwartz|year=2012|title=Life-History Inference in the Early Hominins ''Australopithecus'' and ''Paranthropus''|journal=International Journal of Primatology|volume=33|issue=6|pages=1332–1363|doi=10.1007/s10764-012-9607-2|s2cid=16288970}}</ref>

==Palaeoecology==
''P. boisei'' remains have been found predominantly in what were wet, wooded environments, such as wetlands along lakes and rivers, wooded or arid [[shrubland]]s, and semi-arid woodlands,<ref name=cerling/> with the exception of the savanna-dominated Malawian [[Chiwondo Beds]].<ref name=Bocherens>{{cite journal|first1=H.|last1=Bocherens|first2=O.|last2=Sandrock|first3=O.|last3=Kullmer|first4=F.|last4=Schrenk|year=2011|title=Hominin palaeoecology in late Pliocene Malawi: first insights from isotopes (<sup>13</sup>C, <sup>18</sup>O) in mammal teeth|journal=South African Journal of Science|volume=107|issue=3–4|pages=1–6|doi=10.4102/sajs.v107i3/4.331|doi-access=free}}</ref> Its abundance likely increased during  [[axial precession|precession]]-driven periods of relative humidity while being more rare during intervals of aridity.<ref>{{cite journal |last1=Colcord |first1=Devon E. |last2=Shilling |first2=Andrea M. |last3=Freeman |first3=Katherine H. |last4=Njau |first4=Jackson K. |last5=Stanistreet |first5=Ian G. |last6=Stollhoffen |first6=Harald |last7=Schick |first7=Kathy D. |last8=Toth |first8=Nicholas |last9=Brassell |first9=Simon C. |date=15 June 2019 |title=Aquatic biomarkers record Pleistocene environmental changes at Paleolake Olduvai, Tanzania |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018218309441 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=524 |pages=250–261 |doi=10.1016/j.palaeo.2019.04.001 |bibcode=2019PPP...524..250C |s2cid=133690020 |access-date=22 November 2022}}</ref> During the Pleistocene, there seems 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.<ref>{{cite journal|first=R.|last=Bobe|year=2006|title=The evolution of arid ecosystems in eastern Africa|journal=Journal of Arid Environments|volume=66|issue=3|pages=564–584|doi=10.1016/j.jaridenv.2006.01.010|bibcode=2006JArEn..66..564B}}</ref> Australopithecines and early ''Homo'' likely preferred cooler conditions than later ''Homo'', as there are no australopithecine sites that were below {{cvt|1000|m}} in elevation at the time of deposition. This would mean that, like chimps, they often inhabited areas with an average diurnal temperature of {{cvt|25|C}}, dropping to {{cvt|10|or|5|C}} at night.<ref name=David2016>{{cite journal|first1=T.|last1=Dávid-Barrett|first2=R. I. M.|last2=Dunbar|year=2016|title=Bipedality and hair loss in human evolution revisited: The impact of altitude and activity scheduling|journal=Journal of Human Evolution|volume=94|pages=72–82|doi=10.1016/j.jhevol.2016.02.006|pmc=4874949|pmid=27178459}}</ref>

''P. boisei'' coexisted with ''H. habilis'', ''[[H. rudolfensis]]'' and ''H. ergaster''/''erectus'', but it is unclear how they interacted.<ref name="Tobias2006" /> To explain why ''P. boisei'' was associated with Oldowan tools despite not being the tool maker, Louis Leakey and colleagues, when describing ''H. habilis'' in 1964, suggested that one possibility was ''P. boisei'' was killed by ''H. habilis'',<ref name="Leakey1964">{{cite journal|first1=L.|last1=Leakey|author-link=Louis Leakey|first2=P. V.|last2=Tobias|author-link2=Phillip V. Tobias|first3=J. R.|last3=Napier|author-link3=John R. Napier|year=1964|title=A New Species of the Genus ''Homo'' from Olduvai Gorge|journal=Nature|volume=202|issue=4927|pages=7–9|url=http://users.clas.ufl.edu/krigbaum/proseminar/leakey_etal_nature_1964.pdf|doi=10.1038/202007a0|pmid=14166722|bibcode=1964Natur.202....7L|s2cid=12836722}}</ref> perhaps as food.<ref name="Torre2011">{{cite journal|first=I.|last=de la Torre|year=2011|title=The origins of stone tool technology in Africa: a historical perspective|journal=Philosophical Transactions of the Royal Society B|volume=366|issue=1567|pages=1030|doi=10.1098/rstb.2010.0350|pmc=3049100|pmid=21357225}}</ref> However, when describing ''P. boisei'' 5 years earlier, he said, "There is no reason whatever, in this case, to believe that the skull [OH 5] represents the victim of a cannibalistic feast by some hypothetical more advanced type of man."<ref name="Leakey1959" /> OH 80 seems to have been eaten by a big cat.<ref>{{cite journal|first1=K.|last1=Aramendi|first2=M. C.|last2=Arriaza|first3=J.|last3=Yravedra|display-authors=et al.|year=2019|title=Who ate OH80 (Olduvai Gorge, Tanzania)? A geometric-morphometric analysis of surface bone modifications of a ''Paranthropus boisei'' skeleton|journal=Quaternary International|volume=517|pages=118–130|doi=10.1016/j.quaint.2019.05.029|bibcode=2019QuInt.517..118A|s2cid=181391867|hdl=10366/155561|hdl-access=free}}</ref> The leg OH 35, which either belongs to ''P. boisei'' or ''H. habilis'', shows evidence of [[leopard]] predation.<ref name="Njau2012">{{cite journal|first1=J. K.|last1=Njau|first2=R. J.|last2=Blumenschine|year=2012|title=Crocodylian and mammalian carnivore feeding traces on hominid fossils from FLK 22 and FLK NN 3, Plio-Pleistocene, Olduvai Gorge, Tanzania|journal=Journal of Human Evolution|volume=63|issue=2|pages=408–417|doi=10.1016/j.jhevol.2011.05.008|pmid=21937084}}</ref> Other likely Oldowan predators of great apes include the hunting hyena [[Chasmaporthetes#Species|''Chasmaporthetes nitidula'']], the [[sabertoothed cat]]s ''[[Dinofelis]]'' and ''[[Megantereon]]'',<ref>{{cite journal|first1=J.|last1=Lee-Thorp|first2=J. F.|last2=Thackeray|first3=N. V.|last3=der Merwe|year=2000|title=The hunters and the hunted revisited|journal=Journal of Human Evolution|volume=39|issue=6|pages=565–576|doi=10.1006/jhev.2000.0436|pmid=11102267}}</ref> and the [[crocodile]] ''[[Crocodylus anthropophagus]]''.<ref name=Brochu2010>{{cite journal |first1=C. A.|last1=Brochu|first2=J.|last2=Njau|first3=R. J.|last3=Blumenschine|first4=L. D.|last4=Densmore |year=2010 |title=A New Horned Crocodile from the Plio-Pleistocene Hominid Sites at Olduvai Gorge, Tanzania |journal=PLOS ONE |volume=5 |issue=2 |pages=e9333 |doi=10.1371/journal.pone.0009333 |pmid=20195356 |pmc=2827537|bibcode=2010PLoSO...5.9333B|doi-access=free}}</ref>

==See also==
{{columns-list|colwidth=25em|
* [[African archaeology]]
* {{annotated link|Australopithecus africanus|''Australopithecus africanus''}}
* {{annotated link|Australopithecus sediba|''Australopithecus sediba''}}
* {{annotated link|Homo ergaster|''Homo ergaster''}}
* {{annotated link|Homo habilis|''Homo habilis''}}
* {{annotated link|Homo rudolfensis|''Homo rudolfensis''}}
* {{annotated link|Oldowan}}
* {{annotated link|Paranthropus aethiopicus|''Paranthropus aethiopicus''}}
* {{annotated link|Paranthropus robustus|''Paranthropus robustus''}}
}}

==References==
{{Reflist|30em}}

==Bibliography==
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{{refend}}

==External links==
{{Commons category|Paranthropus boisei}}
{{Commons category|OH 5}}
* [http://www.archaeologyinfo.com/australopithecusboisei.htm Archaeology Info] {{Webarchive|url=https://web.archive.org/web/20110516121601/http://www.archaeologyinfo.com/australopithecusboisei.htm |date=2011-05-16 }}
* ''[http://humanorigins.si.edu/evidence/human-fossils/species/paranthropus-boisei Paranthropus boisei]'' - The Smithsonian Institution's Human Origins Program
* [http://humanorigins.si.edu/evidence/human-evolution-timeline-interactive Human Timeline (Interactive)] – [[Smithsonian Institution|Smithsonian]], [[National Museum of Natural History]] (August 2016).
*[https://web.archive.org/web/20090212172915/http://www.modernhumanorigins.net/oh5.html Images of OH 5]
*[http://www.archaeologyinfo.com/oh5.htm Archaeology Info on OH 5] {{Webarchive|url=https://web.archive.org/web/20110516121434/http://www.archaeologyinfo.com/oh5.htm |date=2011-05-16 }}

{{Human Evolution}}
{{Taxonbar|from=Q310531}}

[[Category:Paranthropus]]
[[Category:Pliocene primates]]
[[Category:Pleistocene primates]]
[[Category:Pleistocene species extinctions]]
[[Category:Mammals described in 1959]]
[[Category:Fossil taxa described in 1959]]
[[Category:Pleistocene mammals of Africa]]
[[Category:Taxa named by Mary Leakey]]