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64-526: Ardipithecus is a genus of an extinct hominine that lived during the Late Miocene and Early Pliocene epochs in the Afar Depression , Ethiopia . Originally described as one of the earliest ancestors of humans after they diverged from the chimpanzees, the relation of this genus to human ancestors and whether it is a hominin is now a matter of debate. Two fossil species are described in

128-432: A 2009 study said that this condition "compromises the living chimpanzee as a behavioral model for the ancestral hominid condition." Bonobo canine size and canine sexual dimorphism more closely resembles that of A. ramidus , and as a result, bonobos are now suggested as a behavioural model. A. ramidus existed more recently than the most recent common ancestor of humans and chimpanzees ( CLCA or Pan - Homo LCA ) and thus

192-644: A brain slightly smaller than men and the Flores hominids ( Homo floresiensis ), nicknamed hobbits, had a cranial capacity of about 380 cm (considered small for a chimpanzee), about a third of the Homo erectus average. It is proposed that they evolved from H. erectus as a case of insular dwarfism. In spite of their smaller brain, there is evidence that H. floresiensis used fire and made stone tools at least as sophisticated as those of their proposed ancestors H. erectus . In this case, it seems that for intelligence,

256-428: A diet that did not depend heavily on foliage, fibrous plant material (roots, tubers, etc.), or hard and or abrasive food. The size of the upper canine tooth in A. ramidus males was not distinctly different from that of females. Their upper canines were less sharp than those of modern common chimpanzees in part because of this decreased upper canine size, as larger upper canines can be honed through wear against teeth in

320-450: A facial aspect, maxillary canines are approximately one millimetre narrower than the central incisor. Their mesial aspects resemble the adjacent lateral incisors, while their distal aspects anticipate the first premolars. They are slightly darker and more yellow in color than the other anterior teeth. From a lingual aspect, they have well developed mesial and distal marginal ridges and a well-developed cingulum. A prominent lingual ridge divides

384-426: A larger brain development due to their change in diet. There has been a gradual increase in brain volume ( brain size ) as the ancestors of modern humans progressed along the timeline of human evolution , starting from about 600 cm in Homo habilis up to 1500 cm in Homo neanderthalensis . However, modern Homo sapiens have a brain volume slightly smaller (1250 cm ) than Neanderthals, women have

448-466: A marker of sexual selection . Studies have suggested that the earliest hominins were dimorphic and that this lessened over the course of the evolution of the genus Homo , correlating with humans becoming more monogamous, whereas gorillas, who live in harems, show a large degree of sexual dimorphism. Concealed (or "hidden") ovulation means that the phase of fertility is not detectable in women, whereas chimpanzees advertise ovulation via an obvious swelling of

512-443: A more primitive walking ability than later hominids, and could not walk or run for long distances. The teeth suggest omnivory , and are more generalised than those of modern apes. Ardipithecus kadabba is "known only from teeth and bits and pieces of skeletal bones", and is dated to approximately 5.6 million years ago. It has been described as a "probable chronospecies " (i.e. ancestor) of A. ramidus . Although originally considered

576-478: A note in the same journal renaming the fossil under a new genus, Ardipithecus . Between 1999 and 2003, a multidisciplinary team led by Sileshi Semaw discovered bones and teeth of nine A. ramidus individuals at As Duma in the Gona area of Ethiopia's Afar Region . The fossils were dated to between 4.35 and 4.45 million years old. Ardipithecus ramidus had a small brain, measuring between 300 and 350 cm. This

640-482: A research team headed by Tim White discovered the first A. ramidus fossils—seventeen fragments including skull, mandible, teeth and arm bones—from the Afar Depression in the Middle Awash river valley of Ethiopia . More fragments were recovered in 1994, amounting to 45% of the total skeleton. This fossil was originally described as a species of Australopithecus , but White and his colleagues later published

704-474: A site called Aramis in the Middle Awash region. Radiometric dating of the layers of volcanic ash encasing the deposits suggest that Ardi lived about 4.3-4.5 million years ago. This date, however, has been questioned by others. Fleagle and Kappelman suggest that the region in which Ardi was found is difficult to date radiometrically, and they argue that Ardi should be dated at 3.9 million years. The fossil

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768-624: A subspecies of A. ramidus , in 2004 anthropologists Yohannes Haile-Selassie , Gen Suwa , and Tim D. White published an article elevating A. kadabba to species level on the basis of newly discovered teeth from Ethiopia . These teeth show "primitive morphology and wear pattern" which demonstrate that A. kadabba is a distinct species from A. ramidus . The specific name comes from the Afar word for "basal family ancestor". Due to several shared characteristics with chimpanzees, its closeness to ape divergence period, and due to its fossil incompleteness,

832-453: Is considered by some to belong, instead of to a subtribe Panina , to its own separate tribe, ( so-called ) "Panini"—which would be a third tribe for Homininae. Some classification schemes provide a more comprehensive account of extinct groups—(see section "Taxonomic Classification", below). For example, tribe Hominini shows two subtribes: subtribe Hominina , which contains at least two extinct genera ; and subtribe Panina, which presents only

896-464: Is extinct. Traces of extinct Homo species, including Homo floresiensis , have been found with dates as recent as 40,000 years ago. Individual members of this subfamily are called hominine or hominines —not to be confused with the terms hominins or Hominini . Until 1970, the family (and term) Hominidae meant humans only; the non-human great apes were assigned to the then-family Pongidae . Later discoveries led to revised classifications, with

960-727: Is not fully representative of that common ancestor. Nevertheless, it is in some ways unlike chimpanzees, suggesting that the common ancestor differs from the modern chimpanzee. After the chimpanzee and human lineages diverged, both underwent substantial evolutionary change. Chimp feet are specialized for grasping trees; A. ramidus feet are better suited for walking. The canine teeth of A. ramidus are smaller, and equal in size between males and females, which suggests reduced male-to-male conflict, increased pair-bonding, and increased parental investment. "Thus, fundamental reproductive and social behavioral changes probably occurred in hominids long before they had enlarged brains and began to use stone tools,"

1024-526: Is only seen in humans, so they argued that the species may show the first trend towards human social, parenting and sexual psychology. Previously, it was assumed that such ancient human ancestors behaved much like chimps, but this is no longer considered to be a viable comparison. This view has yet to be corroborated by more detailed studies of the growth of A.ramidus . The study also provides support for Stephen Jay Gould's theory in Ontogeny and Phylogeny that

1088-440: Is quite uncommon in other primates (and other mammal groups). Canine tooth There are generally four canine teeth: two in the upper (maxillary) and two in the lower (mandibular) arch. A canine is placed laterally to (outside of) each lateral incisor and mesial to (inwards of) the premolars . They are larger and stronger than the incisors, and their roots sink deeply into the bones, causing well-marked prominences upon

1152-416: Is quite unique to humans, at least when compared to other Homininae. Concealed ovulation and menopause in women both also occur in a few other primates however, but are uncommon in other species. Testis and penis size seems to be related to family structure: monogamy or promiscuity , or harem , in humans, chimpanzees or gorillas, respectively. The levels of sexual dimorphism are generally seen as

1216-421: Is regarded by its describers as shedding light on a stage of human evolution about which little was known, more than a million years before Lucy ( Australopithecus afarensis ), the iconic early human ancestor candidate who lived 3.2 million years ago, and was discovered in 1974 just 74 km (46 mi) away from Ardi's discovery site. However, because the "Ardi" skeleton is no more than 200,000 years older than

1280-412: Is single, but longer and thicker than that of the incisors, conical in form, compressed laterally, and marked by a slight groove on each side. The lingual surface also presents two depressions on either side of the surface separated by a ridge in between; these depressions are known as mesial and distal lingual fossae. In humans, the upper canine teeth (popularly called eye teeth, from their position under

1344-455: Is slightly smaller than a modern bonobo or female chimpanzee brain, but much smaller than the brain of australopithecines like Lucy (~400 to 550 cm) and roughly 20% the size of the modern Homo sapiens brain. Like common chimpanzees, A. ramidus was much more prognathic than modern humans. The teeth of A. ramidus lacked the specialization of other apes, and suggest that it was a generalized omnivore and frugivore (fruit eater) with

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1408-401: Is the nearly straight outline this tooth has compared to the maxillary canine which is slightly more bowed. As in the maxillary canine, the mesial incisal edge (or cusp ridge) is shorter than the distal side, however, the cusp is displaced slightly lingual relative to the cusp of the maxillary canine. Lingually, the surface of the tooth is much smoother compared to the very pronounced surface of

1472-686: The Ardipithecus lineage, and this lineage is not literally extinct. A. ramidus was named in September 1994. The first fossil found was dated to 4.4 million years ago on the basis of its stratigraphic position between two volcanic strata : the basal Gaala Tuff Complex (G.A.T.C.) and the Daam Aatu Basaltic Tuff (D.A.B.T.). The name Ardipithecus ramidus stems mostly from the Afar language , in which Ardi means "ground/floor" and ramid means "root". The pithecus portion of

1536-628: The Australopithecus and Homo . Comparison of the tooth root morphology with those of the earlier Sahelanthropus also indicated strong resemblance, also pointing to inclusion to the human line. Evolutionary tree according to a 2019 study: Chimpanzee Ardipithecus Au. afarensis P. aethiopicus P. boisei P. robustus Au. africanus H. floresiensis Au. sediba H. habilis Other Homo The Ardipithecus length measures are good indicators of function and together with dental isotope data and

1600-465: The Homininae–Ponginae last common ancestor ) is estimated at some 14 to 12.5 million years ( Sivapithecus ). Its separation into Gorillini and Hominini (the "gorilla–human last common ancestor", GHLCA) is estimated to have occurred at about 8 to 10 million years ago (T GHLCA ) during the late Miocene , close to the age of Nakalipithecus nakayamai . There is evidence there

1664-598: The human–gorilla last common ancestor . His comparative (narrow allometry ) study in 2011 on the molar and body segment lengths (which included living primates of similar body size) noted that some dimensions including short upper limbs, and metacarpals are reminiscent of humans, but other dimensions such as long toes and relative molar surface area are great ape -like. Sarmiento concluded that such length measures can change back and forth during evolution and are not very good indicators of relatedness ( homoplasy ). However, some later studies still argue for its classification in

1728-407: The social behavior of the species and more ancestral hominids. In particular, it has been used to suggest that the last common ancestor of hominids and African apes was characterized by relatively little aggression between males and between groups. This is markedly different from social patterns in common chimpanzees, among which intermale and intergroup aggression are typically high. Researchers in

1792-793: The Gona Project's physical anthropologist , the fossil evidence from the Middle Awash indicates that both A. kadabba and A. ramidus lived in "a mosaic of woodland and grasslands with lakes, swamps and springs nearby," but further research is needed to determine which habitat Ardipithecus at Gona preferred. Hominine Homininae (the hominines ), is a subfamily of the family Hominidae (hominids). (The Homininae— / h ɒ m ɪ ˈ n aɪ n iː / —encompass humans, and are also called " African hominids " or " African apes ".) This subfamily includes two tribes, Hominini and Gorillini , both having ex tant (or living) species as well as ex tinct species. Tribe Hominini includes:

1856-593: The Homininae tribes diverged not earlier than about 8 million years ago (see Human evolutionary genetics ). Today, chimpanzees and gorillas live in tropical forests with acid soils that rarely preserve fossils. Although no fossil gorillas have been reported, four chimpanzee teeth about 500,000 years old have been discovered in the East-African rift valley ( Kapthurin Formation, Kenya), where many fossils from

1920-402: The ability to now use their hands to create tools or carry things with their hands, the ability to travel longer distances at a faster speed, and the ability to hunt for food. According to researchers, humans were able to be bipedalists due to Darwin's Principle of natural selection . Darwin himself believed that larger brains in humans made an upright gait necessary, but had no hypothesis for how

1984-462: The ages of seventeen and twenty-two months and shed between nine and twelve years. Transposition (positional interchange of two adjacent teeth) is a development defect that most commonly found in the permanent canine, with the maxillary being more commonly seen than mandibular. The upper canine frequently transposed with the first premolar whilst the lower canine transposed with the lateral incisor. Occasionally canines are congenitally missing. From

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2048-412: The base of the skull stopped growing with the brain by the end of juvenility, whereas in chimps it continues growing with the rest of the body into adulthood; and considered this evidence of a switch from a gross skeletal anatomy trajectory to a neurological development trajectory due to selective pressure for sociability. Nonetheless, their conclusions are highly speculative. According to Scott Simpson ,

2112-428: The earliest fossils of Australopithecus , and may in fact be younger than they are, some researchers doubt that it can represent a direct ancestor of Australopithecus . Some researchers infer from the form of her pelvis and limbs and the presence of her abductable hallux , that "Ardi" was a facultative biped : bipedal when moving on the ground, but quadrupedal when moving about in tree branches. A. ramidus had

2176-453: The evidence that Australopithecus were one of the first hominins to evolve into obligate bipedalists. The remains of this subfamily are very important in the field of research as it presents possible information regarding how these primates adapted from tree life to terrestrial life. This was a huge adaptation as it encouraged many evolutionary changes within hominins including the ability to use their hand to make tools and gather food, as well as

2240-442: The evolution of the brain size within the sub family Homininae that tested the genes ASPM ( abnormal spindle-like microcephaly associated) and MCHP1 (microcephalin-1 ) and their association with the human brain. In this study researchers discovered that the increase in brain size is correlated to the increase of both ASP and MCPH1. MCPH1 is very polymorphic in humans compared to gibbons , Old World monkeys . This gene helps encourage

2304-454: The exact position of Ardipithecus in the fossil record is a subject of controversy. Primatologist Esteban Sarmiento had systematically compared and concluded that there is not sufficient anatomical evidence to support an exclusively human lineage. Sarmiento noted that Ardipithecus does not share any characteristics exclusive to humans, and some of its characteristics (those in the wrist and basicranium) suggest it diverged from humans prior to

2368-400: The extant genus Homo , which comprises only one extant species—the modern humans ( Homo sapiens), and numerous extinct human species; and the extant genus Pan , which includes two extant species, chimpanzees and bonobos . Tribe Gorillini ( gorillas ) contains one extant genus, Gorilla, with two extant species, with variants, and one known extinct genus. Alternatively, the genus Pan

2432-590: The extant genus, Pan (chimpanzees/bonobos), as fossils of extinct chimpanzees/bonobos are very rarely found. The Homininae comprise all hominids that arose after the subfamily Ponginae ( orangutans } split from the line of the great apes . The Homininae cladogram has three main branches leading: to gorillas (via the tribe Gorillini); to humans and to chimpanzees (via the tribe Hominini and subtribes Hominina and Panina―(see graphic "Evolutionary tree", below). There are two living species of Panina, chimpanzees and bonobos, and two living species of gorillas and one that

2496-439: The eyes ) are larger and longer than the lower, and usually present a distinct basal ridge. Eruption typically occurs between the ages of eleven and twelve years for upper canines and between nine and ten years for lower canines. Upper deciduous canines also known as the baby tooth, typically erupt between the ages of sixteen and twenty-two months and shed between ten and twelve years. Lower deciduous canines typically erupt between

2560-437: The fauna and flora from the fossil site indicate Ardipithecus was mainly a terrestrial quadruped collecting a large portion of its food on the ground. Its arboreal behaviors would have been limited and suspension from branches solely from the upper limbs rare. A comparative study in 2013 on carbon and oxygen stable isotopes within modern and fossil tooth enamel revealed that Ardipithecus fed both arboreally (on trees) and on

2624-496: The genitals. Women can be partly aware of their ovulation along the menstrual phases, but men are essentially unable to detect ovulation in women. Most primates have semi-concealed ovulation, thus one can think that the common ancestor had semi-concealed ovulation, that was inherited by gorillas, and that later evolved in concealed ovulation in humans and advertised ovulation in chimpanzees. Menopause also occurs in rhesus monkeys , and possibly in chimpanzees, but does not in gorillas and

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2688-428: The great apes then united with humans (now in subfamily Homininae) as members of family Hominidae By 1990, it was recognized that gorillas and chimpanzees are more closely related to humans than they are to orangutans , leading to their (gorillas' and chimpanzees') placement in subfamily Homininae as well. The subfamily Homininae can be further subdivided into three branches, the tribe Gorillini (gorillas),

2752-445: The ground in a more open habitat, unlike chimpanzees. In 2015, Australian anthropologists Gary Clark and Maciej Henneberg said that Ardipithecus adults have a facial anatomy more similar to chimpanzee subadults than adults, with a less-projecting face and smaller canines (large canines in primate males are used to compete within mating hierarchies), and attributed this to a decrease in craniofacial growth in favour of brain growth. This

2816-452: The growth of the brain. Further research indicated that the MCPH1 gene in humans could have also been an encouraging factor of population expansion. Other researchers have included that the diet was an encouraging factor to brain size as protein intake increased this helped brain development. Sexuality is related to family structure and partly shapes it. The involvement of fathers in education

2880-414: The human lineage (hominins) have been found. This shows that some chimpanzees lived close to Homo ( H. erectus or H. rhodesiensis ) at the time; the same is likely true for gorillas. Hominina Pan Graecopithecus Ouranopithecus (†7) Crown Gorillini Chororapithecus (†) Nakalipithecus (†10) Dryopithecini (†) Homininae The age of the subfamily Homininae (of

2944-430: The human lineage. In 2014, it was reported that the hand bones of Ardipithecus , Australopithecus sediba and A. afarensis have the third metacarpal styloid process , which is absent in other apes. Unique brain organisations (such as lateral shift of the carotid foramina, mediolateral abbreviation of the lateral tympanic , and a shortened, trapezoidal basioccipital element) in Ardipithecus are also found only in

3008-411: The lingual aspect in half and creates the mesial and distal lingual fossae between the lingual ridge and the marginal ridges. From a proximal aspect, they resemble the incisors, but are more robust, especially in the cingulum region. Incisally, they are visibly asymmetrical, as the mesial incisal edge is slightly shorter than the distal incisal edge, which places the cusp slightly mesial to the long axis of

3072-405: The literature: A. ramidus , which lived about 4.4 million years ago during the early Pliocene , and A. kadabba , dated to approximately 5.6 million years ago (late Miocene ). Initial behavioral analysis indicated that Ardipithecus could be very similar to chimpanzees, however more recent analysis based on canine size and lack of canine sexual dimorphism indicates that Ardipithecus

3136-455: The lower mouth. The features of the upper canine in A. ramidus contrast with the sexual dimorphism observed in common chimpanzees, where males have significantly larger and sharper upper canine teeth than females. Of the living apes, bonobos have the smallest canine sexual dimorphism, although still greater than that displayed by A. ramidus . The less pronounced nature of the upper canine teeth in A. ramidus has been used to infer aspects of

3200-491: The maxillary canine, and the cingulum is noted as less developed. The cusp may be lost with attrition over time and may resemble an upper second permanent incisor. In many species the canine teeth in the upper or lower jaw, or in both jaws, are much larger in males than in females, where they are sometimes hidden or completely absent. Animals where this occurs include antelopes , musk-deer , camels , horses , wild boar , some apes, seals, narwhal , and walrus . Humans have

3264-591: The mechanism evolved. The first major theory attempting to directly explanation the origins of bipedalism was the Savannah hypothesis (Dart 1925.) This theory hypothesized that hominins became bipedalists due to the environment of the Savanna such as the tall grass and dry climate. This was later proven to be incorrect due to fossil records that showed that hominins were still climbing trees during this era. Anthropologist Owen Lovejoy has suggested that bipedalism

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3328-402: The middle line than the upper, so that their summits correspond to the intervals between the upper canines and the lateral incisors. From a facial aspect, the mandibular canine is notably narrower mesiodistally than the maxillary one, the root is compressed mesiodistally with well-marked grooves on both sides and may be just as long as the maxillary (and at times bifurcated). A distinctive feature

3392-475: The name is from the Greek word for "ape". Like most hominids , but unlike all previously recognized hominins, it had a grasping hallux or big toe adapted for locomotion in the trees. It is not confirmed how many other features of its skeleton reflect adaptation to bipedalism on the ground as well. Like later hominins, Ardipithecus had reduced canine teeth and reduced canine sexual dimorphism. In 1992–1993

3456-455: The paedomorphic (childlike) form of early hominin craniofacial morphology results from dissociation of growth trajectories. Clark and Henneberg also argued that such shortening of the skull—which may have caused a descension of the larynx —as well as lordosis—allowing better movement of the larynx—increased vocal ability, significantly pushing back the origin of language to well before the evolution of Homo . They argued that self domestication

3520-728: The proportionately smallest male canine teeth among all anthropoids and exhibit relatively little sexual dimorphism in canine tooth size. It has been proposed that the receding canine teeth in human males was likely to be a result of sexual selection for less aggressive partners by female humans. The dimorphism is also similarly less pronounced in chimpanzees . In non- synapsids , such as reptiles and crocodiles, teeth similar to canines may be termed "caniniform" ("canine-shaped") teeth. Teeth or appendages with similar appearances found in many snakes and invertebrates, such as spiders, are referred to as fangs , but are usually modified to inject venom. [REDACTED] This article incorporates text in

3584-472: The research team concluded. On October 1, 2009 , paleontologists formally announced the discovery of the relatively complete A. ramidus fossil skeleton first unearthed in 1994. The fossil is the remains of a small-brained 50-kilogram (110 lb) female, nicknamed "Ardi", and includes most of the skull and teeth, as well as the pelvis, hands, and feet. It was discovered in Ethiopia's harsh Afar desert at

3648-402: The structure of the brain is more important than its size. The current size of the human brain is a big distinguishing factor that separates humans from other primates. Recent examination of the human brain shows that the brain of a human is about more than four times the size of great apes and 20 times larger than the brain size of old world monkeys . A study was conducted to help determine

3712-401: The surface. They are the only teeth in dentition with a single cusp, their crowns are roughly triangular from a mesial viewpoint and trapezoidal from a buccal viewpoint . The crown is large and conical, very convex on its labial surface, a little hollowed and uneven on its lingual surface, and tapering to a blunted point or cusp, which projects beyond the level of the other teeth. The root

3776-469: The tooth. They are also thicker labiolingually than mesiodistally. Because of the disproportionate incisal edges, the contacts are also asymmetrical. Mesially, the contact sits at the junction of the incisal and middle third of the crown, while distally, the contact as more cervical, in the middle of the middle third of the crown. The root of the maxillary canines are the longest root of any tooth and conical in shape. The lower canine teeth are placed nearer

3840-423: The tribe Hominini with subtribes Panina (chimpanzees/bonobos) and Hominina (humans and their extinct relatives), and the extinct tribe Dryopithecini . The Late Miocene fossil Nakalipithecus nakayamai , described in 2007, is a basal member of this clade , as is, perhaps, its contemporary Ouranopithecus ; that is, they are not assignable to any of the three extant branches. Their existence suggests that

3904-585: Was a result of sexual dimorphism in efforts to help with the collecting of food. In his Male Provisioning Hypothesis introduced in 1981, lowered birth rates in early hominids increased pressure on males to provide for females and offspring. While females groomed and cared for their children with the family group, males ranged to seek food and returned bipadally with full arms. Males who could better provide for females in this model were more likely to mate and produce offspring. Anthropologist Yohannes Haile-Selassie, an expert on Australopithecus anamensis , discusses

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3968-411: Was aided by the development of vocalization, living in a pro-social society. They conceded that chimps and A. ramidus likely had the same vocal capabilities, but said that A. ramidus made use of more complex vocalizations, and vocalized at the same level as a human infant due to selective pressure to become more social. This would have allowed their society to become more complex. They also noted that

4032-412: Was characterised by reduced aggression, and that they more closely resemble bonobos . Some analyses describe Australopithecus as being sister to Ardipithecus ramidus specifically. This means that Australopithecus is distinctly more closely related to Ardipithecus ramidus than Ardipithecus kadabba . Cladistically , then, Australopithecus (and eventually Homo sapiens ) indeed emerged within

4096-710: Was interbreeding of Gorillas and the Pan–Homo ancestors until right up to the Pan–Homo split. Recent studies of Ardipithecus ramidus (4.4 million years old) and Orrorin tugenensis (6 million years old) suggest some degree of bipedalism. Australopithecus and early Paranthropus may have been bipedal . Very early hominins such as Ardipithecus ramidus may have possessed an arboreal type of bipedalism. The evolution of bipedalism encouraged multiple changes among hominins especially when it came to bipedalism in humans as they were now able to do many other things as they began to walk with their feet. These changes included

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