Ardipithecus

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Ardipithecus
Temporal range: Late Miocene - Early Pliocene, 5.77–4.4  Ma
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Ardi.jpg
Ardipithecus ramidus specimen, nicknamed Ardi
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Hominidae
Subfamily: Homininae
Tribe: Hominini
Subtribe: Hominina
Genus:† Ardipithecus
White et al., 1995
Species

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. [1] Two fossil species are described in the literature: A. ramidus , which lived about 4.4 million years ago [2] during the early Pliocene, and A. kadabba , dated to approximately 5.6 million years ago (late Miocene). [3] Initial behavioral analysis indicated that Ardipithecus could be very similar to chimpanzees, [1] however more recent analysis based on canine size and lack of canine sexual dimorphism indicates that Ardipithecus was characterised by reduced aggression, [4] and that they more closely resemble bonobos. [5]

Contents

Some analyses describe Australopithecus as being sister to Ardipithecus ramidus specifically. [6] This means that Australopithecus is distinctly closer related to Ardipithecus ramidus than Ardipithecus kadabba. Cladistically, then, Australopithecus (and eventually Homo sapiens ) indeed emerged within the Ardipithecus lineage, and this lineage is not literally extinct.

Ardipithecus ramidus

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.). [7] The name Ardipithecus ramidus stems mostly from the Afar language, in which Ardi means "ground/floor" and ramid means "root". The pithecus portion of the name is from the Greek word for "ape". [8]

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. [9]

In 1992–1993 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 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. [10] The fossils were dated to between 4.35 and 4.45 million years old. [11]

Map showing discovery locations. Map of the fossil sites of the earliest hominids (35.8-3.3M BP).svg
Map showing discovery locations.

Ardipithecus ramidus had a small brain, measuring between 300 and 350 cm3. This is slightly smaller than a modern bonobo or female chimpanzee brain, but much smaller than the brain of australopithecines like Lucy (~400 to 550 cm3) and roughly 20% the size of the modern Homo sapiens brain. Like common chimpanzees, A. ramidus was much more prognathic than modern humans. [12]

The teeth of A. ramidus lacked the specialization of other apes, and suggest that it was a generalized omnivore and frugivore (fruit eater) with 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 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. [13] Of the living apes, bonobos have the smallest canine sexual dimorphism, although still greater than that displayed by A. ramidus. [14]

The less pronounced nature of the upper canine teeth in A. ramidus has been used to infer aspects of 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 a 2009 study said that this condition "compromises the living chimpanzee as a behavioral model for the ancestral hominid condition." [13] 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. [15]

A. ramidus existed more recently than the most recent common ancestor of humans and chimpanzees (CLCA or Pan-Homo LCA) and thus 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," the research team concluded. [3]

Ardi

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. [16] It was discovered in Ethiopia's harsh Afar desert at 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. [17]

The fossil 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 the earliest fossils of Australopithecus, and may in fact be younger than they are, [17] 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. [3] [18] [19] A. ramidus had a more primitive walking ability than later hominids, and could not walk or run for long distances. [20] The teeth suggest omnivory, and are more generalised than those of modern apes. [3]

Ardipithecus kadabba

Ardipithecus kadabba fossils Ardipithecus kadabba fossils.jpg
Ardipithecus kadabba fossils

Ardipithecus kadabba is "known only from teeth and bits and pieces of skeletal bones", [16] and is dated to approximately 5.6 million years ago. [3] It has been described as a "probable chronospecies" (i.e. ancestor) of A. ramidus. [3] Although originally considered 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. [21]

The specific name comes from the Afar word for "basal family ancestor". [22]

Classification

Due to several shared characteristics with chimpanzees, its closeness to ape divergence period, and due to its fossil incompleteness, the exact position of Ardipithecus in the fossil record is a subject of controversy. [23] 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 the human–gorilla last common ancestor. [24] 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). [25]

However, some later studies still argue for its classification in 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. [26] 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 the Australopithecus and Homo. [27] Comparison of the tooth root morphology with those of the earlier Sahelanthropus also indicated strong resemblance, also pointing to inclusion to the human line. [28]

Evolutionary tree according to a 2019 study: [29]

Hominini

Paleobiology

The Ardipithecus length measures are good indicators of function and together with dental isotope data and 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. [25] 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 the ground in a more open habitat, unlike chimpanzees. [30]

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 is only seen in humans, so they argued that the species may show the first trend towards human social, parenting and sexual psychology. [31] Previously, it was assumed that such ancient human ancestors behaved much like chimps, but this is no longer considered to be a viable comparison. [32] 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 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 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 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. [33] [31]

According to Scott Simpson, 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. [10]

Anatomically, Ardi is closer to the orangutan than to the chimpanzee, bonobo or gorilla. All three are adapted for knuckle walking on the forest floor and climbing trees. The orangutan spends virtually its entire life in the forest canopy. Its anatomy allows for maximum reach by its upper limbs for overhead branches while its lower limbs have a narrow stance that enables it to balance while walking "foot over foot" on lower branches and vines. Although not as closely related genetically as the knuckle walking apes, this would indicate that Ardi was behaviourly more similar to the orangutan than to the other three great apes. In nature, the orangutan is widely dispersed. There is one dominant male in a territory with wide cheek flaps who maintains contact with others in his territory by vocalizations. The female raises offspring one at a time with a maturation period of about eight years. This is the longest maturation period of any of the apes. During this period, the offspring learns the intricate task of weaving a sleeping platform. Rescue centers are now raising young orangutans that have lost their mother typically from deforestation. They are raised in age cohorts by these centers to learn the necessary skills to be able to be released into the forest. While in these cohorts, they show social behavior reminiscent of age appropriate behavior of human children. This suggests that Ardi was physically preadapted for bipedal locomotion as well as social behavior.[ citation needed ]


See also

Related Research Articles

<span class="mw-page-title-main">Homininae</span> Subfamily of mammals

Homininae, also called "African hominids" or "African apes", is a subfamily of Hominidae. It includes two tribes, with their extant as well as extinct species: 1) the tribe Hominini ―and 2) the tribe Gorillini (gorillas). Alternatively, the genus Pan is sometimes considered to belong to its own third tribe, Panini. Homininae comprises all hominids that arose after orangutans split from the line of great apes. The Homininae cladogram has three main branches, which lead to gorillas, and to humans and chimpanzees via the tribe Hominini and subtribes Hominina and Panina. There are two living species of Panina and two living species of gorillas, but only one extant human species. Traces of extinct Homo species, including Homo floresiensis have been found with dates as recent as 40,000 years ago. Organisms in this subfamily are described as hominine or hominines.

<i>Australopithecus</i> Genus of hominin ancestral to modern humans

Australopithecus is a genus of early hominins that existed in Africa during the Pliocene and Early Pleistocene. The genera Homo, Paranthropus, and Kenyanthropus evolved from some Australopithecus species. Australopithecus is a member of the subtribe Australopithecina, which sometimes also includes Ardipithecus, though the term "australopithecine" is sometimes used to refer only to members of Australopithecus. Species include A. garhi, A. africanus, A. sediba, A. afarensis, A. anamensis, A. bahrelghazali and A. deyiremeda. Debate exists as to whether some Australopithecus species should be reclassified into new genera, or if Paranthropus and Kenyanthropus are synonymous with Australopithecus, in part because of the taxonomic inconsistency.

<i>Australopithecus afarensis</i> Extinct hominid from the Pliocene of East Africa

Australopithecus afarensis is an extinct species of australopithecine which lived from about 3.9–2.9 million years ago (mya) in the Pliocene of East Africa. The first fossils were discovered in the 1930s, but major fossil finds would not take place until the 1970s. From 1972 to 1977, the International Afar Research Expedition—led by anthropologists Maurice Taieb, Donald Johanson and Yves Coppens—unearthed several hundreds of hominin specimens in Hadar, Ethiopia, the most significant being the exceedingly well-preserved skeleton AL 288-1 ("Lucy") and the site AL 333. Beginning in 1974, Mary Leakey led an expedition into Laetoli, Tanzania, and notably recovered fossil trackways. In 1978, the species was first described, but this was followed by arguments for splitting the wealth of specimens into different species given the wide range of variation which had been attributed to sexual dimorphism. A. afarensis probably descended from A. anamensis and is hypothesised to have given rise to Homo, though the latter is debated.

Paleoanthropology or paleo-anthropology is a branch of paleontology and anthropology which seeks to understand the early development of anatomically modern humans, a process known as hominization, through the reconstruction of evolutionary kinship lines within the family Hominidae, working from biological evidence and cultural evidence.

<i>Australopithecus anamensis</i> Extinct hominin from Pliocene east Africa

Australopithecus anamensis is a hominin species that lived approximately between 4.2 and 3.8 million years ago and is the oldest known Australopithecus species, living during the Plio-Pleistocene era.

<span class="mw-page-title-main">Afar Triangle</span> Geological depression caused by the Afar Triple Junction

The Afar Triangle is a geological depression caused by the Afar Triple Junction, which is part of the Great Rift Valley in East Africa. The region has disclosed fossil specimens of the very earliest hominins; that is, the earliest of the human clade, and it is thought by some paleontologists to be the cradle of the evolution of humans. The Depression overlaps the borders of Eritrea, Djibouti and the entire Afar Region of Ethiopia; and it contains the lowest point in Africa, Lake Assal, Djibouti, at 155 m (509 ft) below sea level.

<i>Australopithecus garhi</i> Extinct hominid from the Afar Region of Ethiopia 2.6–2.5 million years ago

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 and the human line, but is now thought to have been an offshoot. Like other australopithecines, A. garhi had a brain volume of 450 cc (27 cu in); a jaw which jutted out (prognathism); relatively large molars and premolars; adaptations for both walking on two legs (bipedalism) and grasping while climbing (arboreality); and it is possible that, though unclear if, males were larger than females. One individual, presumed female based on size, may have been 140 cm tall.

<span class="mw-page-title-main">Hominini</span> Tribe of mammals

The Hominini form a taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera Homo (humans) and Pan and in standard usage excludes the genus Gorilla (gorillas).

<span class="mw-page-title-main">Australopithecine</span> Extinct subtribe of the Hominini tribe, and members of the human clade

Australopithecina or Hominina is a subtribe in the tribe Hominini. The members of the subtribe are generally Australopithecus, and it typically includes the earlier Ardipithecus, Orrorin, Sahelanthropus, and (sometimes) Graecopithecus. All these closely related species are now sometimes collectively termed australopiths or homininians. They are the extinct, close relatives of modern humans and, together with the extant genus Homo, comprise the human clade. Members of the human clade, i.e. the Hominini after the split from the chimpanzees, are now called Hominina.

<span class="mw-page-title-main">Tim D. White</span> American paleoanthropologist

Tim D. White 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 Ardipithecus ramidus, a 4.4 million-year-old likely human ancestor. Prior to that discovery, his early career was notable for his work on Lucy as Australopithecus afarensis with discoverer Donald Johanson.

<span class="mw-page-title-main">Middle Awash</span> UNESCO World Heritage Site in Ethiopia

The Middle Awash is a paleoanthropological research area in the northwest corner of Gabi Rasu in the Afar Region along the Awash River in Ethiopia's Afar Depression. It is a unique natural laboratory for the study of human origins and evolution and a number of fossils of the earliest hominins, particularly of the Australopithecines, as well as some of the oldest known Olduwan stone artifacts, have been found at the site—all of late Miocene, the Pliocene, and the very early Pleistocene times, that is, about 5.6 million years ago (mya) to 2.5 mya. It is broadly thought that the divergence of the lines of the earliest humans (hominins) and of chimpanzees (hominids) was completed near the beginning of that time range, or sometime between seven and five mya. However, the larger community of scientists provide several estimates for periods of divergence that imply a greater range for this event, see CHLCA: human-chimpanzee split.

<i>Ardipithecus kadabba</i> Hominin fossil

Ardipithecus kadabba is the scientific classification given to fossil remains "known only from teeth and bits and pieces of skeletal bones", originally estimated to be 5.8 to 5.2 million years old, and later revised to 5.77 to 5.54 million years old. According to the first description, these fossils are close to the common ancestor of chimps and humans. Their development lines are estimated to have parted 6.5–5.5 million years ago. It has been described as a "probable chronospecies" of A. ramidus. Although originally considered 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.

<i>Ardipithecus ramidus</i> Extinct hominin from Early Pliocene Ethiopia

Ardipithecus ramidus is a species of australopithecine from the Afar region of Early Pliocene Ethiopia 4.4 million years ago (mya). A. ramidus, unlike modern hominids, has adaptations for both walking on two legs (bipedality) and life in the trees (arboreality). However, it would not have been as efficient at bipedality as humans, nor at arboreality as non-human great apes. Its discovery, along with Miocene apes, has reworked academic understanding of the chimpanzee–human last common ancestor from appearing much like modern-day chimpanzees, orangutans and gorillas to being a creature without a modern anatomical cognate.

<span class="mw-page-title-main">Hominidae</span> Family of primates

The Hominidae, whose members are known as the great apes or hominids, are a taxonomic family of primates that includes eight extant species in four genera: Pongo ; Gorilla ; Pan ; and Homo, of which only modern humans remain.

Ardi (ARA-VP-6/500) is the designation of the fossilized skeletal remains of an Ardipithecus ramidus, thought to be an early human-like female anthropoid 4.4 million years old. It is the most complete early hominid specimen, with most of the skull, teeth, pelvis, hands and feet, more complete than the previously known Australopithecus afarensis specimen called "Lucy". In all, 125 different pieces of fossilized bone were found.

The chimpanzee–human last common ancestor (CHLCA) is the last common ancestor shared by the extant Homo (human) and Pan genera of Hominini. Estimates of the divergence date vary widely from thirteen to five million years ago.

Changes to the dental morphology and jaw are major elements of hominid evolution. These changes were driven by the types and processing of food eaten. The evolution of the jaw is thought to have facilitated encephalization, speech, and the formation of the uniquely human chin.

Gen Suwa is a Japanese paleoanthropologist. He is known for his contributions to the understanding of the evolution of early hominids, including the discovery of a tooth from a hominid that was more than one million years older than the oldest previously known hominid. The discovery changed scientific opinion regarding the ancestral splits between humans, chimps and gorillas.

The savannah hypothesis is a hypothesis that human bipedalism evolved as a direct result of human ancestors' transition from an arboreal lifestyle to one on the savannas. According to the hypothesis, hominins left the woodlands that had previously been their natural habitat millions of years ago and adapted to their new habitat by walking upright.

The Middle Awash Project is an international research expedition conducted in the Afar Region of Ethiopia with the goal of determining the olrigins of humanity. The project has the approval of the Ethiopian Culture Ministry and a strong commitment to developing Ethiopian archaeology, paleontology and geology research infrastructure. This project has discovered over 260 fossil specimens and over 17,000 vertebrate fossil specimens to date ranging from 200,000 to 6,000,000 years in age. Researchers have discovered the remains of four hominin species, the earliest subspecies of homo sapiens as well as stone tools. All specimens are permanently held at the National Museum of Ethiopia, where the project’s laboratory work is conducted year round.

References

  1. 1 2 Stanford, Craig B. (2012). "Chimpanzees and the Behavior of Ardipithecus ramidus". Annual Review of Anthropology. 41: 139–49. doi:10.1146/annurev-anthro-092611-145724. SSRN   2158257.
  2. ↑ Perlman, David (July 12, 2001). "Fossils From Ethiopia May Be Earliest Human Ancestor". National Geographic News. Archived from the original on July 15, 2001. Retrieved March 18, 2017. Another co-author is Tim D. White, a paleoanthropologist at UC-Berkeley who in 1994 discovered a pre-human fossil, named Ardipithecus ramidus, that was then the oldest known, at 4.4 million years.
  3. 1 2 3 4 5 6 White, T. D.; Asfaw, B.; Beyene, Y.; Haile-Selassie, Y.; Lovejoy, C. O.; Suwa, G.; Woldegabriel, G. (2009). "Ardipithecus ramidus and the Paleobiology of Early Hominids". Science. 326 (5949): 75–86. Bibcode:2009Sci...326...75W. doi:10.1126/science.1175802. PMID   19810190. S2CID   20189444.
  4. ↑ Wilson, Clare (29 November 2021). "Canine teeth shrank in human ancestors at least 4.5 million years ago". New Scientist. Retrieved 2021-12-01.
  5. ↑ Suwa, Gen; Sasaki, Tomohiko; Semaw, Sileshi; Rogers, Michael J.; Simpson, Scott W.; Kunimatsu, Yutaka; Nakatsukasa, Masato; Kono, Reiko T.; Zhang, Yingqi; Beyene, Yonas; Asfaw, Berhane; White, Tim D. (2021-12-07). "Canine sexual dimorphism in Ardipithecus ramidus was nearly human-like". Proceedings of the National Academy of Sciences. 118 (49). doi: 10.1073/pnas.2116630118 . ISSN   0027-8424. PMC   8670482 . PMID   34853174.
  6. ↑ Pugh, Kelsey (February 2020). The Phylogenetic Relationships of Middle-Late Miocene Apes: Implications for Early Human Evolution (Thesis).
  7. ↑ White, Tim D.; Suwa, Gen; Asfaw, Berhane (1994). "Australopithecus ramidus, a new species of early hominid from Aramis, Ethiopia". Nature. 371 (6495): 306–12. Bibcode:1994Natur.371..306W. doi:10.1038/371306a0. PMID   8090200. S2CID   4347140.
  8. ↑ Tyson, Peter (October 2009). "NOVA, Aliens from Earth: Who's who in human evolution". PBS. Retrieved 2009-10-08.
  9. ↑ #author.fullName}. "Canine teeth shrank in human ancestors at least 4.5 million years ago". New Scientist. Retrieved 2021-12-01.{{cite web}}: |last= has generic name (help)
  10. 1 2 "New Fossil Hominids of Ardipithecus ramidus from Gona, Afar, Ethiopia". Archived from the original on 2008-06-24. Retrieved 2009-01-30.
  11. ↑ "Anthropologists find 4.5 million-year-old hominid fossils in Ethiopia". Indiana University. Retrieved March 18, 2017.
  12. ↑ Suwa, G.; Asfaw, B.; Kono, R. T.; Kubo, D.; Lovejoy, C. O.; White, T. D. (2009). "The Ardipithecus ramidus Skull and Its Implications for Hominid Origins" (PDF). Science. 326 (5949): 68e1–7. Bibcode:2009Sci...326...68S. doi:10.1126/science.1175825. PMID   19810194. S2CID   19725410. Archived (PDF) from the original on 2022-10-09.
  13. 1 2 Suwa, G.; Kono, R. T.; Simpson, S. W.; Asfaw, B.; Lovejoy, C. O.; White, T. D. (2009). "Paleobiological Implications of the Ardipithecus ramidus Dentition" (PDF). Science. 326 (5949): 94–9. Bibcode:2009Sci...326...94S. doi:10.1126/science.1175824. PMID   19810195. S2CID   3744438. Archived (PDF) from the original on 2022-10-09.
  14. ↑ #author.fullName}. "Canine teeth shrank in human ancestors at least 4.5 million years ago". New Scientist. Retrieved 2021-12-01.{{cite web}}: |last= has generic name (help)
  15. ↑ "Science X Network :: Phys.org, Medical Xpress, Tech Xplore". sciencex.com. Retrieved 2021-12-01.
  16. 1 2 Gibbons, A. (2009). "A New Kind of Ancestor: Ardipithecus Unveiled" (PDF). Science. 326 (5949): 36–40. Bibcode:2009Sci...326...36G. doi:10.1126/science.326_36. PMID   19797636. Archived (PDF) from the original on 2022-10-09.
  17. 1 2 Kappelman, John; Fleagle, John G. (1995). "Age of early hominids". Nature . 376 (6541): 558–559. Bibcode:1995Natur.376..558K. doi:10.1038/376558b0. PMID   7503900. S2CID   5527405.
  18. ↑ Shreeve, Jamie (2009-10-01). "Oldest Skeleton of Human Ancestor Found". National Geographic magazine. Archived from the original on October 4, 2009. Retrieved March 18, 2017.
  19. ↑ Gibbons, Ann (October 2009). "Ancient Skeleton May Rewrite Earliest Chapter of Human Evolution". Science . Retrieved March 18, 2017.
  20. ↑ Amos, Jonathan (October 1, 2009). "Fossil finds extend human story". BBC News.
  21. ↑ Haile-Selassie, Y.; Suwa, Gen; White, Tim D. (2004). "Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution". Science. 303 (5663): 1503–5. Bibcode:2004Sci...303.1503H. doi:10.1126/science.1092978. PMID   15001775. S2CID   30387762.
  22. ↑ Ellis, Richard (2004). No Turning Back: The Life and Death of Animal Species . New York: Harper Perennial. pp.  92. ISBN   978-0-06-055804-8.
  23. ↑ Wood, Bernard; Harrison, Terry (2011). "The evolutionary context of the first hominins". Nature . 470 (7334): 347–35. Bibcode:2011Natur.470..347W. doi:10.1038/nature09709. PMID   21331035. S2CID   4428052.
  24. ↑ Sarmiento, E. E. (2010). "Comment on the Paleobiology and Classification of Ardipithecus ramidus". Science. 328 (5982): 1105, author reply 1105. Bibcode:2010Sci...328.1105S. doi:10.1126/science.1184148. PMID   20508113.
  25. 1 2 Sarmiento, E.E.; Meldrum, D.J. (2011). "Behavioral and phylogenetic implications of a narrow allometric study of Ardipithecus ramidus". HOMO. 62 (2): 75–108. doi:10.1016/j.jchb.2011.01.003. PMID   21388620.
  26. ↑ Ward, C. V.; Tocheri, M. W.; Plavcan, J. M.; Brown, F. H.; Manthi, F. K. (2013). "Early Pleistocene third metacarpal from Kenya and the evolution of modern human-like hand morphology". Proceedings of the National Academy of Sciences. 111 (1): 121–4. Bibcode:2014PNAS..111..121W. doi: 10.1073/pnas.1316014110 . PMC   3890866 . PMID   24344276.
  27. ↑ Kimbel, W. H.; Suwa, G.; Asfaw, B.; Rak, Y.; White, T. D. (2014). "Ardipithecus ramidus and the evolution of the human cranial base". Proceedings of the National Academy of Sciences. 111 (3): 948–53. Bibcode:2014PNAS..111..948K. doi: 10.1073/pnas.1322639111 . PMC   3903226 . PMID   24395771.
  28. ↑ Emonet, Edouard-Georges; Andossa, Likius; Taïsso Mackaye, Hassane; Brunet, Michel (2014). "Subocclusal dental morphology of Sahelanthropus tchadensis and the evolution of teeth in hominins". American Journal of Physical Anthropology. 153 (1): 116–23. doi:10.1002/ajpa.22400. PMID   24242778.
  29. ↑ Parins-Fukuchi, C.; Greiner, E.; MacLatchy, L. M.; Fisher, D. C. (2019). "Phylogeny, ancestors and anagenesis in the hominin fossil record" (PDF). Paleobiology. 45 (2): 378–393. doi:10.1017/pab.2019.12. S2CID   196659329. Archived (PDF) from the original on 2022-10-09.
  30. ↑ Nelson, S. V. (2013). "Chimpanzee fauna isotopes provide new interpretations of fossil ape and hominin ecologies". Proceedings of the Royal Society B: Biological Sciences. 280 (1773): 20132324. doi:10.1098/rspb.2013.2324. PMC   3826229 . PMID   24197413.
  31. 1 2 Clark, Gary; Henneberg, Maciej (2015). "The life history of Ardipithecus ramidus: A heterochronic model of sexual and social maturation". Anthropological Review. 78 (2): 109–132. doi: 10.1515/anre-2015-0009 .
  32. ↑ Sayers, Ken; Raghanti, Mary Ann; Lovejoy, C. Owen (2012). "Human Evolution and the Chimpanzee Referential Doctrine". Annual Review of Anthropology. 41: 119–38. doi:10.1146/annurev-anthro-092611-145815. SSRN   2158266.
  33. ↑ Clark, G.; Henneberg, M. (2017). "Ardipithecus ramidus and the evolution of language and singing: An early origin for hominin vocal capability". Homo. 68 (2): 101–121. doi:10.1016/j.jchb.2017.03.001. PMID   28363458.
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