Ardi

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Ardi
Ardipithecis Ramidus skeleton 1994-1996.jpeg
The recovered fragments of Ardi's skeleton
Common nameArdi
Species Ardipithecus ramidus
Age4.4 million years
Place discovered Aramis, Afar, Ethiopia
Date discovered1994
Discovered by Yohannes Haile-Selassie

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, [1] more complete than the previously known Australopithecus afarensis specimen called "Lucy". In all, 125 different pieces of fossilized bone were found. [2]

Contents

Discovery

The Ardi skeleton was discovered at Aramis in the arid badlands near the Awash River in Ethiopia in 1994 by a college student, Yohannes Haile-Selassie, when he uncovered a partial piece of a hand bone. The discovery was made by a team of scientists led by UC Berkeley anthropologist, Tim D. White, [3] [4] [5] and was analyzed by an international group of scientists that included Owen Lovejoy heading the biology team. On 1 October 2009, the journal Science published an open-access collection of eleven articles, detailing many aspects of A. ramidus and its environment. [6] Her fossils were also found near animal remains which indicated that she inhabited a forest type of environment, contrary to the theory that bipedalism originated in savannahs. [7]

Ardi was not the first fossil of A. ramidus to come to light. The first ones were found in Ethiopia in 1992, but it took 17 years to assess their significance. [5]

Etymology

The word Ardi means "ground floor" and the word ramid means "root" in the Afar language, [8] suggesting that Ardi lived on the ground and was the root of the family tree of humanity.

Description

Scientific paleoartist Jay Matternes' rendition of Ardi Ardipithecus ramidus, artistic reconstruction.jpg
Scientific paleoartist Jay Matternes' rendition of Ardi

Ardi weighed about 50 kg (110 lb), and could be up to 120 cm (3.9 ft) tall. Although she is a biped, Ardi had both opposable big toes and thumbs in order to climb trees. It is speculated that her bipedality impeded movement, but enabled her to bear more offspring. [9] : 67 [ clarification needed ]

Although it is not yet clear how Ardi's species is related to Homo sapiens , the discovery is of great significance and added much to the debate on Ardipithecus and its place in human evolution. With regards to Ardi's body composition, archaeologists note that she is unique in that she possesses traits that are characteristic of both extinct primates and early hominids. [9] : 63  It is still a point of debate whether Ardi was capable of bipedal movement. Ardi's divergent big toes are not characteristic of a biped. [9] : 66  However, the found remains of her legs, feet, pelvis, and hands suggested that she walked upright when on the ground but was a quadruped when moving around trees. Her big toe, for example, spreads out quite a bit from her foot to better grasp tree limbs. Unlike chimpanzees, however, her foot contains a unique small bone inside a tendon which kept the big toe stronger. When seen along with Ardi's other bone structures, this unique bone would have helped her walk bipedally, though less efficiently than Lucy. [10] Her wrist bones also provided her with flexibility but the palm bones were short. This suggests that Ardi did not walk on her knuckles and only used her palms to move along tree branches. [11]

Some of Ardi's teeth are still connected to her jawbone and show enamel wear suggesting a diet consisting of fruit and nuts. [9] : 38  The canine teeth of A. ramidus are smaller, and equal in size between males and females. This suggests reduced male-to-male conflict, pair-bonding, and increased parental investment. [12] "Thus fundamental reproductive and social behavioral changes probably occurred in hominids long before they had enlarged brains and began to use stone tools." [13]

Pelvis

Although Ardipithecus had more ancestral hands, feet, and limbs, [14] Ardi's pelvis gives a different perspective. The parts of Ardi's pelvis that were recovered include her left hip, her right ilium, and a fragment of her distal sacrum. [15] A shorter ilium and a curve in the lower spine [15] were the characteristics gathered from these partial remains that indicate Ardi, and the Ardipithecus ramidus species, had the ability to walk upright. [14] The shift to bipedality is only beginning to emerge in Ardi because there are characteristics in Ardi's pelvis that are both found in all later hominids and characteristics that are found in extant African apes. [16] A characteristic that is found in Ardi and in all later hominids is a separate growth site for the anterior inferior iliac spine. [16] A similar ischial structure is a characteristic found in Ardi and in extant African apes. [16] This mixture of characteristics indicates Ardi's bipedality was an earlier version of bipedalism compared to later hominids like Lucy. [15] Regardless of how ancestral Ardi's bipedality was, these characteristics found in Ardi's pelvis show bipedalism was well underway by 4.4 million years ago, even with the ability for arboreal locomotion still present in the hands and limbs. [15]

Ardi's foot is a special area of interest when examining the evolution of bipedalism in early Hominids, and the bipedality of Ardipithecus ramidus, because all five toes do not line up. [17] The remains of the foot from Ardi and other Ardipithecus ramidus specimens that can be studied includes "a talus, medial and intermediate cuneiforms, cuboid, first, second, third, and fifth metatarsals, and several phalanges. [18] " The foot of Ardi contains an opposable hallux (big toe) that is similar to chimpanzees. [14] This opposable hallux is believed to have been used to aid in tree climbing. [14] On the outside, Ardi's foot may look like it belongs with other Apes, but on the inside, Ardi's foot contains a bone called the os peroneum, which allows the bottom of the foot to be more rigid. [17] The rigidity of the bottom of the foot was believed to allow Ardi to walk upright, and the other four toes that were aligned performed the "toe off" action during a bipedal motion. [17] The combination of features found in Ardi's and other Ardipithecus ramidus foot bones captures a moment in time where these primitive primates were beginning to leave the trees and spending longer periods of time on the ground. [17]

See also

Related Research Articles

<i>Ardipithecus</i> Extinct genus of hominins

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 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. 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 was characterised by reduced aggression, and that they more closely resemble bonobos.

<span class="mw-page-title-main">Bipedalism</span> Terrestrial locomotion using two limbs

Bipedalism is a form of terrestrial locomotion where an animal 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'. Types of bipedal movement include walking or running and hopping.

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

Australopithecus (, OS-trə-lə-PITH-i-kəs, -⁠loh-; or 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.

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

Australopithecus anamensis is a hominin species that lived approximately between 4.3 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.

<span class="mw-page-title-main">Knuckle-walking</span> Form of quadrupedal walking using the knuckles

Knuckle-walking is a form of quadrupedal walking in which the forelimbs hold the fingers in a partially flexed posture that allows body weight to press down on the ground through the knuckles. Gorillas and chimpanzees use this style of locomotion, as do anteaters and platypuses.

<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.

<span class="mw-page-title-main">Arches of the foot</span> Load-bearing curves in the tarsal and metatarsal bones of the feet

The arches of the foot, formed by the tarsal and metatarsal bones, strengthened by ligaments and tendons, allow the foot to support the weight of the body in the erect posture with the least weight.

<span class="mw-page-title-main">Third trochanter</span>

In human anatomy, the third trochanter is a bony projection occasionally present on the proximal femur near the superior border of the gluteal tuberosity. When present, it is oblong, rounded, or conical in shape and sometimes continuous with the gluteal ridge. It generally occurs bilaterally without significant side to side dimorphism. A structure of minor importance in humans, the incidence of the third trochanter varies from 17 to 72% between ethnic groups and it is frequently reported as more common in females than in males. Structures analogous to the third trochanter are present in other mammals, including some primates, but also in horses. It is called the third trochanter in reference to the greater and lesser trochanters that are always present on the femur.

<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">Human skeletal changes due to bipedalism</span> Evoltionary changes to the human skeleton as a consequence of bipedalism

The evolution of human bipedalism, which began in primates approximately four million years ago, or as early as seven million years ago with Sahelanthropus, or approximately twelve million years ago with Danuvius guggenmosi, has led to morphological alterations to the human skeleton including changes to the arrangement, shape, and size of the bones of the foot, hip, knee, leg, and the vertebral column. These changes allowed for the upright gait to be overall more energy efficient in comparison to quadrupeds. The evolutionary factors that produced these changes have been the subject of several theories that correspond with environmental changes on a global scale.

Claude Owen Lovejoy[a] is an evolutionary anthropologist and anatomist at Kent State University Ohio. He is best known for his work on Australopithecine locomotion and the origins of bipedalism. "The origin of man", which he published in Science in January 1981, is cited as among his best-known articles. The 'C' of his name stands for Claude, but he never uses the name and is known only as Owen.

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.

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 origins 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.

Pliopapio is an extinct genus of Old World monkey known from the latest part of the Miocene to the early Pliocene Epochs from the Afar Region of Ethiopia. It was first described based on a very large series of fossils from the site of Aramis in the Middle Awash, which has been dated by 40Ar/39Ar to 4.4 million years old. It has since been found from similarly aged sediments at Gona, approximately 75 km to the North. Additional fossils from the Middle Awash extend its known time range back to at least 5.3 million years ago. There is only one known species, Pliopapio alemui.

References

  1. ↑ Ann Gibbons (2 October 2009). "A new kind of ancestor: Ardipithecus unveiled". Science . 326 (5949): 36–40. doi:10.1126/science.326.5949.36. PMID   19797636 . Retrieved June 23, 2013.
  2. ↑ Lemonick, Michael D.; Dorfman, Andrea (2009-10-01). "Ardi Is a New Piece for the Evolution Puzzle". Time. ISSN   0040-781X . Retrieved 2017-10-01.
  3. ↑ Lemonick, M. D.; Dorfman, D. (1 October 2009). "Ardi is a new piece for the evolution puzzle". Time . Archived from the original on June 1, 2010. Retrieved October 6, 2009.
  4. ↑ Achenbach, J. (2 October 2009). "'Ardi' may rewrite the story of humans: 1.4 million-year-old primate helps bridge evolutionary gap". The Washington Post . Retrieved October 3, 2009.
  5. 1 2 Amos, J. (1 October 2009). "Fossil finds extend human story". The BBC . Archived from the original on 6 October 2009. Retrieved October 6, 2009.
  6. ↑ "Online extras: Ardipithecus ramidus". Science. Archived from the original on 5 October 2009. Retrieved October 6, 2009.
  7. ↑ Ardipithecus Ramidus, Smithsonian's National Museum of Natural History, The Smithsonian Institution's Human Origins Program, 2010, retrieved November 17, 2016
  8. ↑ "Who's Who in Human Evolution". NOVA. PBS. Retrieved 2009-10-08.
  9. 1 2 3 4 Shreeve, Jamie (July 2010). "The Evolutionary Road". The National Geographic, Print . Vol. 218, no. 1. pp. 38–67.
  10. ↑ Shreeve, Jamie (2009-10-01). "Oldest Modern Human Outside of Africa Found". National Geographic . Archived from the original on October 27, 2010. Retrieved 2016-12-01.
  11. ↑ Dorey, Fran, Ardipithecus Ramidus, The Australian Museum , retrieved 2016-12-01
  12. ↑ Lovejoy, C. Owen (2009-10-02), "Reexamining human origins in light of Ardipithecus ramidus" (PDF), Science, 326 (74): 74e1–8, Bibcode:2009Sci...326...74L, doi:10.1126/science.1175834, PMID   19810200, S2CID   42790876
  13. ↑ "Oldest Skeleton of Human Ancestor Found". National Geographic. October 2009. Archived from the original on October 4, 2009. Retrieved 2009-10-01.
  14. 1 2 3 4 Shook, Beth; Nelson, Katie; Aguilera, Kelsie; Braff, Lara; Eds (9 December 2019). "Early Hominins". University of Hawaii . Retrieved 13 December 2023.
  15. 1 2 3 4 Lovejoy, C. Owen; Suwa, Gen; Spurlock, Linda; Asfaw, Berhane; White, Tim D. (2009-10-02). "The Pelvis and Femur of Ardipithecus ramidus: The Emergence of Upright Walking". Science. 326 (5949): 71e1–6. Bibcode:2009Sci...326...71L. doi:10.1126/science.1175831. PMID   19810197. S2CID   19505251.
  16. 1 2 3 White, Tim D.; Asfaw, Berhane; Beyene, Yonas; Haile-Selassie, Yohannes; Lovejoy, C. Owen; Suwa, Gen; WoldeGabriel, Giday (2009-10-02). "Ardipithecus ramidus and the Paleobiology of Early Hominids". Science. 326 (5949): 64–86. Bibcode:2009Sci...326...75W. doi:10.1126/science.1175802. S2CID   20189444.
  17. 1 2 3 4 Shreeve, Jamie (2010-07-01). "The Birth of Bipedalism". National Geographic. 218 (1): 61–67 – via Ebsco Host.
  18. ↑ Lovejoy, C. Owen; Latimer, Bruce; Suwa, Gen; Asfaw, Berhane; White, Tim D. (2009-10-02). "Combining Prehension and Propulsion: The Foot of Ardipithecus ramidus". Science. 326 (5949): 72e1–8. Bibcode:2009Sci...326...72L. doi:10.1126/science.1175832. PMID   19810198. S2CID   26778544.
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