Jump to content

Ardipithecus: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
m Reverted edits by 146.87.0.77 (talk) to last version by Rjwilmsi
Line 29: Line 29:
== ''Ardipithecus ramidus'' ==
== ''Ardipithecus ramidus'' ==
[[Image:Map of the fossil sites of the earliest hominids (35.8-3.3M BP).svg|thumb|left|Map showing discovery location]]
[[Image:Map of the fossil sites of the earliest hominids (35.8-3.3M BP).svg|thumb|left|Map showing discovery location]]
''A. ramidus'' was named in September 1994. The first fossil find was dated to 4.4 million years ago based on its interval between two volcanic [[stratum|strata]]: the basal [[Tuff|Gaala Tuff Complex]] (GATC) and the [[basalt|Daam Aatu Basaltic Tuff]] (DABT).<ref>{{cite doi|10.1038/371306a0}}</ref> 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 language|Greek]] word for "ape".<ref name="NOVA">{{cite web | title=NOVA, Aliens from Earth: Who's who in human evolution | last=Tyson | first=Peter | year=2009 | month=October | publisher=PBS | accessdate=2009-10-08 | url=http://www.pbs.org/wgbh/nova/hobbit/tree-nf.html}}</ref> Its distinguishing characteristics are [[bipedalism]] incorporating an [[arboreal]] grasping [[hallux]] or big toe, reduced [[Canine tooth|canine teeth]] and a smaller brain size comparable to that of the modern [[chimpanzee]].
''A. ramidus'' was named in September 1994. The first fossil find was dated to 4.4 million years ago based on its interval between two volcanic [[stratum|strata]]: the basal [[Tuff|Gaala Tuff Complex]] (GATC) and the [[basalt|Daam Aatu Basaltic Tuff]] (DABT).<ref>{{cite doi|10.1038/371306a0}}</ref> 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 language|Greek]] word for "ape".<ref name="NOVA">{{cite web | title=NOVA, Aliens from Earth: Who's who in human evolution | last=Tyson | first=Peter | year=2009 | month=October | publisher=PBS | accessdate=2009-10-08 | url=http://www.pbs.org/wgbh/nova/hobbit/tree-nf.html}}</ref> Its distinguishing characteristics are [[bipedalism]] incorporating an [[arboreal]] grasping [[hallux]] or big toe, reduced [[Canine tooth|canine teeth]] and a smaller brain size comparable to that of the modern king kongs thumb [[chimpanzee]].


In 1992–1993 a research team headed by [[Tim D. White|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]] Western Margin of Ethiopia's [[Afar Region]].<ref name="stoneageinstitute.org">{{cite web |title=New Fossil Hominids of Ardipithecus ramidus from Gona, Afar, Ethiopia |url=http://www.stoneageinstitute.org/news/gona_nature_paper.shtml#1 |accessdate=2009-01-30 | archiveurl=http://web.archive.org/web/20080624005441/http://www.stoneageinstitute.org/news/gona_nature_paper.shtml |archivedate=2008-06-24}}</ref> The fossils were dated to between 4.32 and 4.51 million years old.<ref>{{cite web | url=http://newsinfo.iu.edu/news/page/normal/1822.html | author = Indiana University News Release | title = Anthropologists find 4.5 million-year-old hominid fossils in Ethiopia | accessdate = 2009-01-30}}</ref>
In 1992–1993 a research team headed by [[Tim D. White|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]] Western Margin of Ethiopia's [[Afar Region]].<ref name="stoneageinstitute.org">{{cite web |title=New Fossil Hominids of Ardipithecus ramidus from Gona, Afar, Ethiopia |url=http://www.stoneageinstitute.org/news/gona_nature_paper.shtml#1 |accessdate=2009-01-30 | archiveurl=http://web.archive.org/web/20080624005441/http://www.stoneageinstitute.org/news/gona_nature_paper.shtml |archivedate=2008-06-24}}</ref> The fossils were dated to between 4.32 and 4.51 million years old.<ref>{{cite web | url=http://newsinfo.iu.edu/news/page/normal/1822.html | author = Indiana University News Release | title = Anthropologists find 4.5 million-year-old hominid fossils in Ethiopia | accessdate = 2009-01-30}}</ref>

Revision as of 10:59, 10 May 2011

Ardipithecus
Temporal range: Pliocene
Ardipithecus ramidus specimen, nicknamed Ardi
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Mammalia
Order:
Primates
Family:
Hominidae
Subfamily:
Homininae
Tribe:
Hominini
Genus:
Ardipithecus

White et al., 1995
Species

†Ardipithecus kadabba
†Ardipithecus ramidus

Ardipithecus is a very early hominin genus. Two species are described in the literature: A. ramidus, which lived about 4.4 million years ago[1] during the early Pliocene, and A. kadabba, dated to approximately 5.6 million years ago (late Miocene).[2]

Ardipithecus ramidus

Map showing discovery location

A. ramidus was named in September 1994. The first fossil find was dated to 4.4 million years ago based on its interval between two volcanic strata: the basal Gaala Tuff Complex (GATC) and the Daam Aatu Basaltic Tuff (DABT).[3] 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".[4] Its distinguishing characteristics are bipedalism incorporating an arboreal grasping hallux or big toe, reduced canine teeth and a smaller brain size comparable to that of the modern king kongs thumb chimpanzee.

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 Western Margin of Ethiopia's Afar Region.[5] The fossils were dated to between 4.32 and 4.51 million years old.[6]

Ardipithecus ramidus had a small brain, measuring between 300 and 350 cm3. This is about the same size as a modern bonobo or female common 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.[7]

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 fibrous plants, ripe fruit or hard or abrasive food. The size of the upper canine tooth in A. ramidus males was not distinctly different than 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 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.[8]

The less pronounced nature of 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."[8]

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.[2]

Ardi

Main article: Ardi
Casts of Ardi's finger bones

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.[9] 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 4.4 million years ago. This date however has been questioned by others. Beagle 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.[10]

The fossil sheds 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.

Researchers infer from the form of her pelvis and limbs and the presence of her abductable hallux, that she was a facultative biped: bipedal when moving on the ground, but quadrupedal when moving about in tree branches.[2][11][12] A. ramidus had a more primitive walking ability than later hominids, and could not walk or run for long distances.[13] The teeth suggest omnivory, and are more generalised than those of modern apes.[2]

Ardipithecus kadabba

Ardipithecus kadabba fossils

Ardipithecus kadabba is "known only from teeth and bits and pieces of skeletal bones",[9] and is dated to approximately 5.6 million years ago.[2] It has been described as a "probable chronospecies" (i.e. ancestor) of A. ramidus.[2] 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.[14]

The specific name comes from the Afar word for "basal family ancestor".[15]

Lifestyle

The toe and pelvic structure of A. ramidus suggests that the creature walked upright.[5]

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.[5]

See also

References

  1. ^ Perlman, David (July 12, 2001). "Fossils From Ethiopia May Be Earliest Human Ancestor". National Geographic News. Retrieved July 2009. 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. {{cite web}}: Check date values in: |accessdate= (help)
  2. ^ a b c d e f White, Tim D. (2009). "Ardipithecus ramidus and the Paleobiology of Early Hominids". Science. 326 (5949): 75–86. doi:10.1126/science.1175802. PMID 19810190. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1038/371306a0, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1038/371306a0 instead.
  4. ^ Tyson, Peter (2009). "NOVA, Aliens from Earth: Who's who in human evolution". PBS. Retrieved 2009-10-08. {{cite web}}: Unknown parameter |month= ignored (help)
  5. ^ a b c "New Fossil Hominids of Ardipithecus ramidus from Gona, Afar, Ethiopia". Archived from the original on 2008-06-24. Retrieved 2009-01-30.
  6. ^ Indiana University News Release. "Anthropologists find 4.5 million-year-old hominid fossils in Ethiopia". Retrieved 2009-01-30.
  7. ^ Suwa, G; Asfaw, B.; Kono, R. T.; Kubo, D.; Lovejoy, C. O.; White, T. D.; et al. (2 October 2009). "The Ardipithecus ramidus skull and its implications for hominid origins". Science. 326 (5949): 68, 68e1–68e7. doi:10.1126/science.1175825. PMID 19810194. {{cite journal}}: Explicit use of et al. in: |first= (help)
  8. ^ a b Suwa, G; Kono, R. T.; Simpson, S. W.; Asfaw, B.; Lovejoy, C. O.; White, T. D.; et al. (2 October 2009). "Paleobiological implications of the Ardipithecus ramidus dentition". Science. 326 (5949): 69, 94–99. doi:10.1126/science.1175824. PMID 19810195. {{cite journal}}: Explicit use of et al. in: |first= (help)
  9. ^ a b Gibbons, Ann (2009). "A New Kind of Ancestor: Ardipithecus Unveiled". Science. 326 (5949): 36–40. doi:10.1126/science.326_36. PMID 19797636. {{cite journal}}: Cite has empty unknown parameter: |coauthors= (help)
  10. ^ Kappelman, John; Beagle, John G. (1995). "Age of early homonids". Nature. 376 (6541): 558–559. doi:10.1038/376558b0.
  11. ^ Jamie Shreeve (2009-10-01). "Oldest Skeleton of Human Ancestor Found". National Geographic magazine. Retrieved 2009-10-01.
  12. ^ Ann Gibbons. "Ancient Skeleton May Rewrite Earliest Chapter of Human Evolution". Science magazine. Retrieved 2009-10-01.
  13. ^ Amos, Jonathan (2009-10-01). "Fossil finds extend human story". BBC News.
  14. ^ Haile-Selassie, Yohannes (2004). "Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution". Science. 303 (5663): 1503–1505. doi:10.1126/science.1092978. PMID 15001775. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  15. ^ Ellis, Richard (2004). No Turning Back: The Life and Death of Animal Species. New York: Harper Perennial. p. 92. ISBN 0-06-055804-0.
Wikispecies has information related to Ardipithecus.
Wikimedia Commons has media related to Ardipithecus.
Retrieved from "https://wiki.riteme.site/w/index.php?title=Ardipithecus&oldid=428402239"