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''Australopithecus garhi'' is a species of australopithecine from the Bouri Formation in the Afar Region of Ethiopia 2.6–2.5 million years ago (mya) during the Early Pleistocene. The first remains were described in 1999 based on several skeletal elements uncovered in the three years preceding. ''A. garhi'' was originally considered to have been a direct ancestor to ''
Homo ''Homo'' () is the genus that emerged in the (otherwise extinct) genus '' Australopithecus'' that encompasses the extant species ''Homo sapiens'' (modern humans), plus several extinct species classified as either ancestral to or closely relat ...
'' and the human line, but is now thought to have been an offshoot. Like other australopithecines, ''A. garhi'' had a brain volume of ; a jaw which jutted out (
prognathism Prognathism, also called Habsburg jaw or Habsburgs' jaw primarily in the context of its prevalence amongst members of the House of Habsburg, is a positional relationship of the mandible or maxilla to the skeletal base where either of the jaws pr ...
); relatively large molars and premolars; adaptations for both walking on two legs (
bipedalism Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...
) and grasping while climbing (
arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose num ...
ity); and it is possible that, though unclear if, males were larger than females (exhibited
sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
). One individual, presumed female based on size, may have been tall. ''A. garhi'' is the first pre-''Homo'' hominin postulated to have manufactured tools—using them in butchering—and may be counted among a growing body of evidence for pre-''Homo'' stone tool industries (the ability to manufacture tools was previously believed to have separated ''Homo'' from predecessors.) ''A. garhi'' possibly produced the Oldowan industry which was previously considered to have been invented by the later '' H. habilis'', though this may have instead been produced by contemporary ''Homo''.


Taxonomy

The Ethiopian ''Australopithecus garhi'' was first described in 1999 by palaeoanthropologists Berhane Asfaw,
Tim D. White Tim D. White (born August 24, 1950) is an American paleoanthropologist and Professor of Integrative Biology at the University of California, Berkeley. He is best known for leading the team which discovered Ardi, the type specimen of ''Ardipithecu ...
, Owen Lovejoy, Bruce Latimer, Scott Simpson, and Gen Suwa based on fossils discovered in the Hatayae Beds of the Bouri Formation in Middle Awash, Afar Region, Ethiopia. The first hominin remains were discovered here in 1990—a partial parietal bone (GAM-VP-1/2), left jawbone (GAM-VP-1/1), and left
humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...
(MAT-VP-1/1)—which are unassignable to a specific
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
. The first identifiable ''Australopithecus'' fossils–an adult
ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
(BOU-VP-11/1)–were found on 17 November 1996 by T. Assebework. A partial skeleton (BOU-VP-12/1) was discovered 13 days later by White, comprising a mostly complete left
femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...
, right
humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...
,
radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
, and
ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
, and a partial
fibula The fibula or calf bone is a human leg, leg bone on the Lateral (anatomy), lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long ...
, foot, and jawbone. The holotype specimen, a partial skull (BOU-VP-12/130), was discovered on 20 November 1997 by Ethiopian palaeoanthropologist Yohannes Haile-Selassie. More skull fragments (BOU-VP-12/87) were recovered south of BOU-VP-12/1. On 17 November 1997, French palaeoanthropologist Alban Defleur discovered a complete mandible (BOU-VP-17/1) about north in the Esa Dibo locality of the formation, and American palaeoanthropologist David DeGusta discovered a humerus (BOU-VP-35/1) north of BOU-VP-17/1. However, BOU-VP-11, -12, and -35 cannot conclusively be attributed to ''A. garhi''. The remains are dated to about 2.5 million years ago (mya) based on argon–argon dating. When they were discovered, human evolution was obscured due to a paucity of remains from 3 to 2 mya, with the only
hominin The Hominini form a taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos) and in standard usage excludes the genus ''Gorilla'' (gorillas). The t ...
s from this timespan being identified from South Africa ('' A. africanus'') and Lake Turkana, Kenya ('' Paranthropus aethiopicus''). Likewise, the classification of australopithecines and pre-''
Homo erectus ''Homo erectus'' (; meaning " upright man") is an extinct species of archaic human from the Pleistocene, with its earliest occurrence about 2 million years ago. Several human species, such as ''H. heidelbergensis'' and ''H. antecessor' ...
'' hominins has been the subject of much debate. The original describers considered ''A. garhi'' to be a descendant of the earlier '' A. afarensis'' which inhabited the same region, based mainly on dental similarities. Though they assigned the species to ''
Australopithecus ''Australopithecus'' (, ; ) is a genus of early hominins that existed in Africa during the Late Pliocene and Early Pleistocene. The genus ''Homo'' (which includes modern humans) emerged within ''Australopithecus'', as sister to e.g. ''Austral ...
'', the original describers believed it could represent an ancestor to ''Homo'', which, if the case, would possibly lead to reclassification as ''H. garhi''. Because the characteristics of ''A. garhi'' are unexpected for a human ancestor at this stage, the
specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...
, ''garhi'', means "surprise" in the local Afar language. In 1999, American palaeoanthropologists David Strait and Frederick E. Grine concluded that ''A. garhi'' was instead an offshoot of the human line instead of an ancestor because ''A. garhi'' and ''Homo'' share no
synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...
(traits unique to only them). In 2015, ''Homo'' was recorded from 2.8 mya, much earlier than ''A. garhi''.


Anatomy

Like other australopithecines, ''A. garhi'' had a brain volume of about , a sagittal crest running along the midline of the skull, and a
prognathic Prognathism, also called Habsburg jaw or Habsburgs' jaw primarily in the context of its prevalence amongst members of the House of Habsburg, is a positional relationship of the mandible or maxilla to the skeletal base where either of the jaws pr ...
jaw (the jaw jutted out). Relatively, the postcanine teeth, the molars and premolars, are massive ( post-canine megadontia), similar to or greater than those of other australopithecines and of the large-toothed ''
Paranthropus robustus ''Paranthropus robustus'' is a species of robust australopithecine from the Early and possibly Middle Pleistocene of the Cradle of Humankind, South Africa, about 2.27 to 0.87 (or, more conservatively, 2 to 1) million years ago. It has been iden ...
''. Like the earlier ''A. afarensis'' from the same region, ''A. garhi'' had a humanlike humerus to femur ratio, and an apelike brachial index (lower to upper arm ratio) as well as curved phalanges of the hand. This is generally interpreted as adaptations for both walking on two legs (habitual
bipedalism Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...
) as well as for grasping while climbing in trees (
arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose num ...
ity). The BOU-VP-35/1 humerus specimen is notably larger than the humerus of the BOU-VP-12/1 specimen, which could potentially indicate size-specific
sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
with males larger than females to a similar degree to what is postulated in ''A. afarensis'', but it is unclear if this does not represent normal size variation of the same sex as this is based on only two specimens. Nonetheless, on the basis of size, BOU-VP-12/130 is considered male and BOU-VP-17/1 female. Contemporary hominins from Kenya are about the same size as ''A. garhi''. BOU-VP-17/1 may have been about tall. ''Australopithecus'' are thought to have had fast, apelike growth rates, lacking an extended childhood typical of modern humans. However, the legs of ''A. garhi'' are elongated, unlike those of other ''Australopithecus'', and, in humans, elongated limbs develop during the delayed adolescent growth spurt. This could mean that ''A. garhi'', compared to other ''Australopithecus'', either had a slower overall growth rate, or a more rapid leg growth rate.


Palaeoecology

The large teeth of ''Australopithecus'' species have historically been interpreted as having been adaptations for a diet of hard foods, but the durable teeth may instead have only served an important function during leaner times for harder fallback foods. That is, dental anatomy may not accurately portray normal ''Australopithecus'' diet, rather abnormal diet during times of famine. Though it was not found with any tools, mammalian bones associated with the ''A. garhi'' remains exhibit cut and percussion marks made from stone tools: the left
mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bon ...
of an alcelaphine bovid with three successive, unambiguous cut marks presumably made while removing the tongue; a bovid tibia with cut marks, chop marks, and impact scars from a
hammerstone In archaeology, a hammerstone is a hard cobble used to strike off lithic flakes from a lump of tool stone during the process of lithic reduction. The hammerstone is a rather universal stone tool which appeared early in most regions of the w ...
, possibly inflicted to harvest the
bone marrow Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It is composed of hematopoieti ...
; and a '' Hipparion'' (a horse) femur with cut marks consistent with dismemberment and filleting. As to why stone tools were not present, because the Hatayae locality was likely a featureless, grassy lake margin with so few raw materials for making stone tools, it is possible these hominins were creating and carrying tools some ways with them to butchering sites, intending to use them many times before discarding. It was previously believed that only ''
Homo ''Homo'' () is the genus that emerged in the (otherwise extinct) genus '' Australopithecus'' that encompasses the extant species ''Homo sapiens'' (modern humans), plus several extinct species classified as either ancestral to or closely relat ...
'' could manufacture tools; but it is also possible that the butcherers were not manufacturing tools and simply used naturally sharp rocks. At the nearby Gona site, where there is an abundance of raw materials, several Oldowan tools (an industry previously believed to have been invented by '' H. habilis'') were recovered from 1992 to 1994. The tools date to around 2.6–2.5 mya, the oldest evidence of manufacturing at the time, and since ''A. garhi'' was the only species identified in the vicinity at the time, this species was the best candidate for authorship. However, in 2015, the earliest remains of ''Homo'',
LD 350-1 LD 350-1 is the earliest known specimen of the genus ''Homo'', dating to 2.8–2.75 million years ago (mya), found in the Ledi-Geraru site in the Afar Region of Ethiopia. The specimen was discovered in silts above the Gurumaha Tuff section of ...
, were discovered in Ledi-Geraru, also in the Afar Region, dating to 2.8–2.75 mya. More stone tools were found in 2019 dating to about 2.6 mya in Ledi-Geraru, predating the Gona artifacts, and these may be attributed to ''Homo''; the invention of sharp-edged Oldowan tools could actually be due to specific adaptations characteristic of ''Homo''. Nonetheless, other australopithecines have been associated with stone tool manufacturing, such as the 2010 discovery of cut marks dating to 3.4 mya attributed to ''A. afarensis'', and the 2015 discovery of the Lomekwi culture from Lake Turkana dating to 3.3 mya possibly attributed to '' Kenyanthropus''.


See also


References


External links


Reconstruction
by Viktor Deak * *
Human Timeline (Interactive)
Smithsonian,
National Museum of Natural History The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with ...
(August 2016). * {{Taxonbar, from=Q310527 Australopithecus Pliocene primates Mammals described in 1997 Fossil taxa described in 1997 Prehistoric Ethiopia Pliocene mammals of Africa