Ardipithecus ramidus: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
No edit summary
No edit summary
Line 1: Line 1:
{{short description|Species of mammal (fossil)}}
{{short description|Species of mammal (fossil)}}
{{Speciesbox
{{Speciesbox
| fossil_range = [[Zanclean]] {{fossil range|4.5|4.35}}
| fossil_range = [[Zanclean]] {{fossil range|4.5|4.32}}
| image = Ardipithecus ramidus.jpg
| image = Ardipithecus ramidus.jpg
| image_alt = A skull
| image_alt = A skull
Line 12: Line 12:
}}
}}


'''''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 [[hominid]]s, has adaptations for both life in the trees ([[arboreal]]ity) and walking on two legs ([[biped]]ality). However, it would not have been as efficient at arboreality as modern apes, nor at bipedality as humans. Its discovery, along with [[Miocene]] apes, has reworked academic understanding of the [[chimpanzee-human last common ancestor]] from appearing much like modern day [[chimp]]s, [[orangutan]]s, and [[gorilla]]s to being a creature without a modern anatomical cognate.
'''''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 [[hominid]]s, has adaptations for both walking on two legs ([[biped]]ality) and life in the trees ([[arboreal]]ity). However, it would not have been as efficient at bipedality as humans, nor 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 [[chimp]]s, [[orangutan]]s, and [[gorilla]]s to being a creature without a modern anatomical cognate.


The facial anatomy suggests that ''A. ramidus'' males were less aggressive than those of modern [[chimp]]s, which is correlated to increased parental care and [[monogamy]] in primates. It was capable of both [[suspensory behavior]] in the trees and walking [[biped]]ally, whereas modern apes are specialized for either or; consequently, it was less adapted in either habitat compared to modern specialized counterparts. It has also been suggested that it was among the earliest of human ancestors to use some proto-language, possibly capable of vocalizing at the same level as a human infant. ''A. ramidus'' appears to have inhabited [[woodland]] and [[bushland]] corridors between savannas.
The facial anatomy suggests that ''A. ramidus'' males were less aggressive than those of modern chimps, which is correlated to increased parental care and [[monogamy]] in primates. It has also been suggested that it was among the earliest of human ancestors to use some proto-language, possibly capable of vocalizing at the same level as a human infant. ''A. ramidus'' appears to have inhabited [[woodland]] and [[bushland]] corridors between savannas.


==Taxonomy==
==Taxonomy==
[[Image:Map of the fossil sites of the earliest hominids (35.8-3.3M BP).svg|thumb|left|Map showing discovery locations of various [[australopithecine]]s]]
[[Image:Map of the fossil sites of the earliest hominids (35.8-3.3M BP).svg|thumb|left|Map showing discovery locations of various [[australopithecine]]s]]
The first remains were described in 1994 by American anthropologist [[Tim D. White]], Japanese paleoanthropologist [[Gen Suwa]], and Ethiopian paleontologist [[Berhane Asfaw]]. The [[holotype specimen]], ARA-VP-6/1, comprised an associated set of 10 teeth; and there were 16 other [[paratype]]s identified, preserving also skull and arm fragments. These were unearthed in the 4.4 million year (Ma) deposits of the [[Afar region]] in [[Aramis, Ethiopia]] from 1992 to 1993. They classified it as ''Australopithecus ramidus'', the [[species name]] deriving from the [[Afar language]] ''ramid'' "root". In 1995, they made a [[corrigendum]], recommending the species be split off into a separate genus from ''Australopithecus''.<ref name=White1994>{{Cite journal|last1=White |first1=T. D.|last2=Suwa |first2=G. |last3=Asfaw |first3=B. |title=''Australopithecus ramidus'', a new species of early hominid from Aramis, Ethiopia |journal=Nature |volume=371 |pages=306–312 |year=1994 |pmid=8090200 |doi=10.1038/371306a0|url=http://www2.ku.edu/~lba/courses/articles/White%20ramadis94.pdf |bibcode=1994Natur.371..306W|issue=6495 |url-status=dead |archiveurl=https://web.archive.org/web/20130413081635/http://www2.ku.edu/~lba/courses/articles/White%20ramadis94.pdf |archivedate=2013-04-13 }}</ref> ''Ardipithecus'' stems from Afar ''ardi'' "ground" and [[Ancient Greek]] ''pithecus'' "ape".
The first remains were described in 1994 by American anthropologist [[Tim D. White]], Japanese paleoanthropologist [[Gen Suwa]], and Ethiopian paleontologist [[Berhane Asfaw]]. The [[holotype specimen]], ARA-VP-6/1, comprised an associated set of 10 teeth; and there were 16 other [[paratype]]s identified, preserving also skull and arm fragments. These were unearthed in the 4.4 million year (Ma) deposits of the [[Afar region]] in [[Aramis, Ethiopia]] from 1992 to 1993. They classified it as ''Australopithecus ramidus'', the [[species name]] deriving from the [[Afar language]] ''ramid'' "root". In 1995, they made a [[corrigendum]], recommending the species be split off into a separate genus from ''Australopithecus''.<ref name=White1994>{{Cite journal|last1=White |first1=T. D.|authorlink=Tim D. White|last2=Suwa |first2=G.|authorlink2=Gen Suwa|last3=Asfaw |first3=B. |authorlink3=Berhane Asfaw|title=''Australopithecus ramidus'', a new species of early hominid from Aramis, Ethiopia |journal=Nature |volume=371 |pages=306–312 |year=1994 |pmid=8090200 |doi=10.1038/371306a0|url=http://www2.ku.edu/~lba/courses/articles/White%20ramadis94.pdf |bibcode=1994Natur.371..306W|issue=6495 |url-status=dead |archiveurl=https://web.archive.org/web/20130413081635/http://www2.ku.edu/~lba/courses/articles/White%20ramadis94.pdf |archivedate=2013-04-13 }}</ref> ''Ardipithecus'' stems from Afar ''ardi'' "ground" and [[Ancient Greek]] ''pithecus'' "ape".


Fossils from at least nine ''A. ramidus'' individuals at [[As Duma]], [[Gona Western Margin]], Afar, were unearthed from 1993–2003. The fossils were dated to between 4.32 and 4.51 million years ago.<ref>{{cite journal|first=S.|last=Semaw|first2=S. W.|last2=Simpson|display-authors=et al.|year=2005|title=Early Pliocene hominids from Gona, Ethiopia|journal=Nature|volume=433|issue=7023|pages=301–305|doi=10.1038/nature03177|pmid=15662421}}</ref>
About 45% of the total skeleton is known. Between 1999 and 2003, a team led by [[Sileshi Semaw]] from the [[Stone Age Institute]] 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=https://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 4.35 and 4.45 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| archiveurl= https://web.archive.org/web/20090214231444/http://newsinfo.iu.edu/news/page/normal/1822.html| archivedate= 14 February 2009 | url-status= live}}</ref>


In 2001, 6.5–5.5 million year old fossils from the [[Middle Awash]] were classified as a subspecies of ''A. ramidus'' by Ethiopian paleoanthropologist [[Yohannes Haile-Selassie]].<ref>{{cite journal|first=Y.|last=Haile-Selassie|authorlink=Yohannes Haile-Selassie|year=2001|title=Late Miocene hominids from the Middle Awash, Ethiopia|journal=Nature|volume=42|issue=6843|pages=179–181|doi=10.1038/35084063|pmid=11449272}}</ref> In 2004, Haile-Selassie, Suwa, and White split it off into its own species, ''[[Ardipithecus kadabba|A. kadabba]]''.<ref>{{cite journal |last=Haile-Selassie |first=Y.|authorlink=Yohannes Haile-Selassie|last2=Suwa|first2=G.|authorlink2=Gen Suwa|last3=White|first3=T. D.|authorlink3=Tim D. White|date=2004 |title=Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution |journal=Science |volume=303 |issue=5663 |pages=1503–1505 |doi=10.1126/science.1092978 |pmid=15001775 |bibcode = 2004Sci...303.1503H }}</ref>
In 2001, 6.5–5.5 million year old fossils from the [[Middle Awash]] were classified as a subspecies of ''A. ramidus'' by Ethiopian paleoanthropologist [[Yohannes Haile-Selassie]].<ref>{{cite journal|first=Y.|last=Haile-Selassie|authorlink=Yohannes Haile-Selassie|year=2001|title=Late Miocene hominids from the Middle Awash, Ethiopia|journal=Nature|volume=42|issue=6843|pages=179–181|doi=10.1038/35084063|pmid=11449272}}</ref> In 2004, Haile-Selassie, Suwa, and White split it off into its own species, ''[[Ardipithecus kadabba|A. kadabba]]''.<ref>{{cite journal |last=Haile-Selassie |first=Y.|authorlink=Yohannes Haile-Selassie|last2=Suwa|first2=G.|authorlink2=Gen Suwa|last3=White|first3=T. D.|authorlink3=Tim D. White|date=2004 |title=Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution |journal=Science |volume=303 |issue=5663 |pages=1503–1505 |doi=10.1126/science.1092978 |pmid=15001775 |bibcode = 2004Sci...303.1503H }}</ref>


In 2009, White and colleagues reaffirmed the position of ''Ardipithecus'' as a [[hominin]] more closely related to modern humans than to [[chimp]]s based on dental similarity, a short [[base of the skull]], and adaptations to [[biped]]ality.<ref name="AndThePaleobiology"/> In 2011, primatologist [[Esteban Sarmiento]] said that there is not enough evidence to assign ''Ardipithecus'' to Hominini,<ref name=Sarmiento2011/> but its closer affinities to ''[[Homo]]'' than chimps have been reaffirmed in following years.<ref>{{cite journal|first=W. H.|last=Kimbel|first2=G.|last2=Suwa|first3=B.|last3=Asfaw|first4=Y.|last4=Rak|first5=T. D.|last5=White|authorlink5=Tim White|year=2014|title=''Ardipithecus ramidus'' and the evolution of the human cranial base|journal=Proceedings of the National Academy of Sciences|volume=111|issue=3|pages=948–953|doi=10.1073/pnas.1322639111|pmc=3903226|pmid=24395771}}</ref><ref name=White2015/>
In 2009, White and colleagues reaffirmed the position of ''Ardipithecus'' as a [[hominin]] more closely related to modern humans than to [[chimp]]s based on dental similarity, a short [[base of the skull]], and adaptations to [[biped]]ality.<ref name="AndThePaleobiology"/> In 2011, primatologist [[Esteban Sarmiento]] said that there is not enough evidence to assign ''Ardipithecus'' to Hominini,<ref name=Sarmiento2011/> but its closer affinities to ''[[Homo]]'' than chimps have been reaffirmed in following years.<ref>{{cite journal|first=W. H.|last=Kimbel|first2=G.|last2=Suwa|authorlink2=Gen Suwa|first3=B.|last3=Asfaw|authorlink3=Berhane Asfaw|first4=Y.|last4=Rak|first5=T. D.|last5=White|authorlink5=Tim White|year=2014|title=''Ardipithecus ramidus'' and the evolution of the human cranial base|journal=Proceedings of the National Academy of Sciences|volume=111|issue=3|pages=948–953|doi=10.1073/pnas.1322639111|pmc=3903226|pmid=24395771}}</ref><ref name=White2015/>


[[Evolutionary tree]] according to a 2019 study:<ref name=Parins2019>{{cite journal|first=C.|last=Parins-Fukuchi|first2=E.|last2=Greiner|first3=L. M.|last3=MacLatchy|first4=D. C.|last4=Fisher|year=2019|title=Phylogeny, ancestors and anagenesis in the hominin fossil record|journal=Paleobiology|volume=45|issue=2|pages=378–393|doi=10.1017/pab.2019.12|url=https://www.biorxiv.org/content/biorxiv/early/2018/10/05/434894.full.pdf}}</ref>
[[Evolutionary tree]] according to a 2019 study:<ref name=Parins2019>{{cite journal|first=C.|last=Parins-Fukuchi|first2=E.|last2=Greiner|first3=L. M.|last3=MacLatchy|first4=D. C.|last4=Fisher|year=2019|title=Phylogeny, ancestors and anagenesis in the hominin fossil record|journal=Paleobiology|volume=45|issue=2|pages=378–393|doi=10.1017/pab.2019.12|url=https://www.biorxiv.org/content/biorxiv/early/2018/10/05/434894.full.pdf}}</ref>
Line 63: Line 63:
}}}}}}}}
}}}}}}}}


⚫
[[File:Ardipithecis Ramidus skeleton 1994-1996.jpeg|thumb|upright=0.7|"[[Ardi]]", the most complete ''Ardipithecus'' specimen]]
Before the discovery of ''Ardipithecus'' and other pre-''Australopithecus'' hominins, it was assumed that the [[chimpanzee–human last common ancestor]] and preceding apes appeared much like modern day chimps, orangutans, and gorillas, which would have meant these three changed very little over millions of years. Their discovery led to the postulation that modern great apes, much like humans, evolved several specialized adaptations to their environment (have highly [[derived]] morphologies), and their ancestors were comparatively poorly adapted to [[suspensory behavior]] or knuckle walking, and did not have such a specialized diet. Also, the origins of bipedality were thought to have occurred due to a switch from a forest to a savanna environment, but the presence of bipedal pre-''Australopithecus'' hominins in [[woodland]]s has called this into question,<ref name=Lovejoy2009c/> though they inhabited wooded corridors near or between savannas.<ref name=Cerling2010/> It is also possible that ''Ardipithecus'' and pre-''Australopithecus'' were random offshoots of the hominin line.
Before the discovery of ''Ardipithecus'' and other pre-''Australopithecus'' hominins, it was assumed that the [[chimpanzee–human last common ancestor]] and preceding apes appeared much like modern day chimps, orangutans, and gorillas, which would have meant these three changed very little over millions of years. Their discovery led to the postulation that modern great apes, much like humans, evolved several specialized adaptations to their environment (have highly [[derived]] morphologies), and their ancestors were comparatively poorly adapted to [[suspensory behavior]] or knuckle walking, and did not have such a specialized diet. Also, the origins of bipedality were thought to have occurred due to a switch from a forest to a savanna environment, but the presence of bipedal pre-''Australopithecus'' hominins in [[woodland]]s has called this into question,<ref name=Lovejoy2009c/> though they inhabited wooded corridors near or between savannas.<ref name=Cerling2010/> It is also possible that ''Ardipithecus'' and pre-''Australopithecus'' were random offshoots of the hominin line.


==Description==
==Description==
⚫
One of the larger specimens from Aramis, ARA-VP-6/500, was estimated to have stood {{cvt|124|cm|ftin|sigfig=1}} and weighed {{cvt|51|kg}} based on comparisons with large-bodied female apes. Another specimen, A.L. 288-1, was estimated to have weighed {{cvt|26|kg}}. Assuming subsistence was primarily sourced from climbing in trees, ''A. ramidus'' may not have exceeded {{cvt|35–60|kg}}.<ref>{{cite journal|first=C. O.|last=Lovejoy|authorlink=Owen Lovejoy (anthropologist)|first2=G.|last2=Suwa|authorlink2=Gen Suwa|first3=S. W.|last3=Simpson|first4=J. H.|last4=Matternes|first5=T. D.|last5=White|authorlink5=Tim D. White|year=2009|title=The Great Divides: ''Ardipithecus ramidus'' Reveals the Postcrania of Our Last Common Ancestors with African Apes|journal=Science|volume=326|issue=5949|pages=73–106|doi=10.1126/science.1175833}}</ref>
⚫
[[File:Ardipithecis Ramidus skeleton 1994-1996.jpeg|thumb|upright=0.7|"[[Ardi]]", the most complete ''Ardipithecus'' specimen]]
⚫
One of the larger specimens from Aramis, ARA-VP-6/500, was estimated to have stood {{cvt|124|cm|ftin|sigfig=1}} and weighed {{cvt|51|kg}} based on comparisons with large-bodied female apes. Another specimen, A.L. 288-1, was estimated to have weighed {{cvt|26|kg}}. Assuming subsistence was primarily sourced from climbing in trees, ''A. ramidus'' may not have exceeded {{cvt|35–60|kg}}.<ref>{{cite journal|first=C. O.|last=Lovejoy|first2=G.|last2=Suwa|authorlink2=Gen Suwa|first3=S. W.|last3=Simpson|first4=J. H.|last4=Matternes|first5=T. D.|last5=White|authorlink5=Tim D. White|year=2009|title=The Great Divides: ''Ardipithecus ramidus'' Reveals the Postcrania of Our Last Common Ancestors with African Apes|journal=Science|volume=326|issue=5949|pages=73–106|doi=10.1126/science.1175833}}</ref>


''A. ramidus'' had a small brain, measuring {{cvt|300–350|cc}}. This is slightly smaller than a modern [[bonobo]] or [[chimp]] brain, but much smaller than the brain of ''[[Australopithecus]]''–about {{cvt|400|–|550|cc}}–and roughly 20% the size of the modern human brain. Like chimps, the ''A. ramidus'' face was much more pronounced ([[Prognathism|prognathic]]) than modern humans.<ref name="Suwa_2009">{{cite journal | title=The ''Ardipithecus ramidus skull'' and its implications for hominid origins | journal=Science | last=Suwa | first=G | date=2 October 2009| volume=326 | issue=5949 | pages=68, 68e1–68e7 | doi=10.1126/science.1175825 | last2=Asfaw | first2=B. | last3=Kono | first3=R. T. | last4=Kubo | first4=D. | last5=Lovejoy | first5=C. O. | last6=White | first6=T. D. | pmid=19810194|bibcode = 2009Sci...326...68S |display-authors=etal| url=http://doc.rero.ch/record/211453/files/PAL_E4442.pdf }}</ref> The size of the upper [[canine tooth]] in ''A. ramidus'' males was not distinctly different from that of females, in contrast to the [[sexual dimorphism]] observed in chimps where males have significantly larger and sharper upper canines than females.<ref name="Suwa_2009b">{{cite journal | title=Paleobiological implications of the ''Ardipithecus ramidus'' dentition | journal=Science | date=2 October 2009| last=Suwa | first=G | volume=326 | issue=5949 | pages=69, 94–99 | doi=10.1126/science.1175824 | last2=Kono | first2=R. T. | last3=Simpson | first3=S. W. | last4=Asfaw | first4=B. | last5=Lovejoy | first5=C. O. | last6=White | first6=T. D. | pmid=19810195|bibcode = 2009Sci...326...94S |display-authors=etal| url=http://doc.rero.ch/record/211460/files/PAL_E4443.pdf }}</ref>
''A. ramidus'' had a small brain, measuring {{cvt|300–350|cc}}. This is slightly smaller than a modern [[bonobo]] or chimp brain, but much smaller than the brain of ''[[Australopithecus]]''–about {{cvt|400|–|550|cc}}–and roughly 20% the size of the modern human brain. Like chimps, the ''A. ramidus'' face was much more pronounced ([[Prognathism|prognathic]]) than modern humans.<ref name="Suwa_2009">{{cite journal | title=The ''Ardipithecus ramidus'' skull and its implications for hominid origins | journal=Science | last=Suwa | first=G.|authorlink=Gen Suwa|year= 2009| volume=326 | issue=5949 | pages=68, 68e1–68e7 | doi=10.1126/science.1175825 | last2=Asfaw | first2=B. |authorlink2=Berhane Asfaw| last3=Kono | first3=R. T. | last4=Kubo | first4=D. | last5=Lovejoy | first5=C. O.|authorlink5=Owen Lovejoy (anthropologist)| last6=White | first6=T. D. |authorlink6=Tim D. White| pmid=19810194|bibcode = 2009Sci...326...68S |display-authors=etal| url=http://doc.rero.ch/record/211453/files/PAL_E4442.pdf }}</ref> The size of the upper [[canine tooth]] in ''A. ramidus'' males was not distinctly different from that of females, in contrast to the [[sexual dimorphism]] observed in chimps where males have significantly larger and sharper upper canines than females.<ref name="Suwa_2009b">{{cite journal | title=Paleobiological implications of the ''Ardipithecus ramidus'' dentition | journal=Science | year=2009| last=Suwa | first=G. |authorlink=Gen Suwa| volume=326 | issue=5949 | pages=69, 94–99 | doi=10.1126/science.1175824 | last2=Kono | first2=R. T. | last3=Simpson | first3=S. W. | last4=Asfaw | first4=B. |authorlink4=Berhane Asfaw| last5=Lovejoy | first5=C. O. |authorlink5=Owen Lovejoy (anthropologist)| last6=White | first6=T. D. |authorlink6=Tim D. White| pmid=19810195|bibcode = 2009Sci...326...94S |display-authors=etal| url=http://doc.rero.ch/record/211460/files/PAL_E4443.pdf }}</ref>


[[File:Ardipithecus Gesamt1.jpg|thumb|left|Reconstruction of ''Ardipithecus'' skeleton]]
''A. ramidus'' feet are better suited for walking than chimps. However, like most [[great ape]]s, but unlike all previously recognized hominins, it had a grasping big toe adapted for locomotion in the trees (an [[arboreal]] lifestyle), though it was likely not as specialized for grasping as it is in modern great apes.<ref name=Lovejoy2009b/><ref name="AndThePaleobiology"/> Its [[tibia]]l and [[tarsus (skeleton)|tarsal]] lengths indicate a leaping ability similar to bonobos.<ref name=Sarmiento2011>{{cite journal|first=E. E.|last=Sarmiento|authorlink=Esteban Sarmiento|first2=D. J.|last2=Meldrum|year=2011|title=Behavioral and phylogenetic implications of a narrow allometric study of ''Ardipithecus ramidus''|journal=HOMO|volume=62|issue=2|pages=75–108|doi=10.1016/j.jchb.2011.01.003}}</ref> It lacks any characters suggestive of specialized [[suspensory behaviour|suspension]], vertical climbing, or [[knuckle walking]]; and it seems to have used a method of locomotion unlike any modern great ape, which combined arboreal [[palmigrade|palm walking]] clambering and a form of bipedality more primitive than ''Australopithecus''. The discovery of such unspecialized locomotion led American anthropologist [[Owen Lovejoy (anthropologist)|Owen Lovejoy]] and colleagues to postulate that the [[chimpanzee–human last common ancestor]] used a similar method of locomotion.<ref>{{cite journal|first=C. O.|last=Lovejoy|first2=S. W.|last2=Simpson|first3=T. D.|last3=White|authorlink3=Tim D. White|first4=B.|last4=Asfaw|authorlink4=Berhane Asfaw|first5=G.|last5=Suwa|authorlink5=Gen Suwa|year=|title=Careful Climbing in the Miocene: The Forelimbs of ''Ardipithecus ramidus'' and Humans Are Primitive|journal=Science|volume=326|issue=5949|pages=70–70e8|doi=10.1126/science.1175827}}</ref><ref name="AndThePaleobiology"/>
''A. ramidus'' feet are better suited for walking than chimps. However, like non-human great apes, but unlike all previously recognized human ancestors, it had a grasping big toe adapted for locomotion in the trees (an [[arboreal]] lifestyle), though it was likely not as specialized for grasping as it is in modern great apes.<ref name=Lovejoy2009b/><ref name="AndThePaleobiology"/> Its [[tibia]]l and [[tarsus (skeleton)|tarsal]] lengths indicate a leaping ability similar to bonobos.<ref name=Sarmiento2011>{{cite journal|first=E. E.|last=Sarmiento|authorlink=Esteban Sarmiento|first2=D. J.|last2=Meldrum|year=2011|title=Behavioral and phylogenetic implications of a narrow allometric study of ''Ardipithecus ramidus''|journal=HOMO|volume=62|issue=2|pages=75–108|doi=10.1016/j.jchb.2011.01.003}}</ref> It lacks any characters suggestive of specialized [[suspensory behaviour|suspension]], vertical climbing, or [[knuckle walking]]; and it seems to have used a method of locomotion unlike any modern great ape, which combined arboreal [[palmigrade|palm walking]] clambering and a form of bipedality more primitive than ''Australopithecus''. The discovery of such unspecialized locomotion led American anthropologist [[Owen Lovejoy (anthropologist)|Owen Lovejoy]] and colleagues to postulate that the chimpanzee–human last common ancestor used a similar method of locomotion.<ref>{{cite journal|first=C. O.|last=Lovejoy|authorlink=Owen Lovejoy (anthropologist)|first2=S. W.|last2=Simpson|first3=T. D.|last3=White|authorlink3=Tim D. White|first4=B.|last4=Asfaw|authorlink4=Berhane Asfaw|first5=G.|last5=Suwa|authorlink5=Gen Suwa|year=2009|title=Careful Climbing in the Miocene: The Forelimbs of ''Ardipithecus ramidus'' and Humans Are Primitive|journal=Science|volume=326|issue=5949|pages=70–70e8|doi=10.1126/science.1175827}}</ref><ref name="AndThePaleobiology"/>


The upper pelvis (distance from the [[sacrum]] to the [[hip joint]]) is shorter than in any known ape. It is inferred to have had a long [[lumbar vertebra]]l series, and [[lordosis]] (human curvature of the spine), which are adaptations for bipedality. However, the legs were not completely aligned with the torso (were anterolaterally displaced), and ''Ardipithecus'' may have relied more on its [[quadriceps]] than [[hamstrings]] for walking (the opposite is true for modern humans).<ref name=Lovejoy2009a>{{cite journal|first=C. O.|last=Lovejoy|first2=G.|last2=Suwa|authorlink2=Gen Suwa|first3=L.|last3=Spurlock|first4=B.|last4=Asfaw|authorlink4=Berhane Asfaw|first5=T. D.|last5=White|authorlink5=Tim D. White|year=2009|title=The Pelvis and Femur of ''Ardipithecus ramidus'': The Emergence of Upright Walking|journal=Science|volume=326|issue=5949|pages=71–71e6|doi=10.1126/science.1175831}}</ref> However, it lacked [[foot arch]]es and had to adopt a flat-footed stance. These would have made it less efficient at walking and running than ''Australopithecus'' and ''Homo''. It may not have employed a bipedal gait for very long time intervals.<ref name=White2015>{{cite journal|first=T. D.|last=White|authorlink=Tim White|first2=C. O.|last2=Lovejoy|first3=B.|last3=Asfaw|authorlink3=Berhane Asfaw|first4=J. P.|last4=Carlson|first5=G.|last5=Suwa|authorlink5=Gen Suwa|year=2015|title=Neither chimpanzee nor human, ''Ardipithecus'' reveals the surprising ancestry of both|journal=Proceedings of the National Academy of Sciences|volume=112|issue=16|pages=4877–4884|doi=10.1073/pnas.1403659111|pmc=4413341|pmid=25901308}}</ref> It may have predominantly used palm walking on the ground,<ref>{{cite journal|first=T. C.|last=Prang|year=2019|title=The African ape-like foot of ''Ardipithecus ramidus'' and its implications for the origin of bipedalism|journal=eLife|volume=8|pages=e44433|doi=10.7554/eLife.44433|pmc=6491036|pmid=31038121}}</ref> Nonetheless, ''A. ramidus'' still had specialized adaptations for bipedality, such as a robust [[fibularis longus]] muscle used in pushing the foot off the ground while walking ([[plantarflexion]]).<ref name=Lovejoy2009b>{{cite journal|first=C. O.|last=Lovejoy|first2=B.|last2=Latimar|first3=G.|last3=Suwa|authorlink3=Gen Suwa|first4=B.|last4=Asfaw|authorlink4=Berhane Asfaw|first5=T. D.|last5=White|authorlink5=Tim D. White|year=2011|title=Combining Prehension and Propulsion: The Foot of ''Ardipithecus ramidus''|journal=Science|volume=326|issue=5949|pages=72-72e8|doi=10.1126/science.1175832|pmid=19810198}}</ref>
The upper pelvis (distance from the [[sacrum]] to the [[hip joint]]) is shorter than in any known ape. It is inferred to have had a long [[lumbar vertebra]]l series, and [[lordosis]] (human curvature of the spine), which are adaptations for bipedality. However, the legs were not completely aligned with the torso (were anterolaterally displaced), and ''Ardipithecus'' may have relied more on its [[quadriceps]] than [[hamstrings]] for walking (the opposite is true for modern humans).<ref name=Lovejoy2009a>{{cite journal|first=C. O.|last=Lovejoy||authorlink=Owen Lovejoy (anthropologist)|first2=G.|last2=Suwa|authorlink2=Gen Suwa|first3=L.|last3=Spurlock|first4=B.|last4=Asfaw|authorlink4=Berhane Asfaw|first5=T. D.|last5=White|authorlink5=Tim D. White|year=2009|title=The Pelvis and Femur of ''Ardipithecus ramidus'': The Emergence of Upright Walking|journal=Science|volume=326|issue=5949|pages=71–71e6|doi=10.1126/science.1175831}}</ref> However, it lacked [[foot arch]]es and had to adopt a flat-footed stance. These would have made it less efficient at walking and running than ''Australopithecus'' and ''Homo''. It may not have employed a bipedal gait for very long time intervals.<ref name=White2015>{{cite journal|first=T. D.|last=White|authorlink=Tim White|first2=C. O.|last2=Lovejoy|first3=B.|last3=Asfaw|authorlink3=Berhane Asfaw|first4=J. P.|last4=Carlson|first5=G.|last5=Suwa|authorlink5=Gen Suwa|year=2015|title=Neither chimpanzee nor human, ''Ardipithecus'' reveals the surprising ancestry of both|journal=Proceedings of the National Academy of Sciences|volume=112|issue=16|pages=4877–4884|doi=10.1073/pnas.1403659111|pmc=4413341|pmid=25901308}}</ref> It may have predominantly used palm walking on the ground,<ref>{{cite journal|first=T. C.|last=Prang|year=2019|title=The African ape-like foot of ''Ardipithecus ramidus'' and its implications for the origin of bipedalism|journal=eLife|volume=8|pages=e44433|doi=10.7554/eLife.44433|pmc=6491036|pmid=31038121}}</ref> Nonetheless, ''A. ramidus'' still had specialized adaptations for bipedality, such as a robust [[fibularis longus]] muscle used in pushing the foot off the ground while walking ([[plantarflexion]]),<ref name=Lovejoy2009b>{{cite journal|first=C. O.|last=Lovejoy|first2=B.|last2=Latimar|first3=G.|last3=Suwa|authorlink3=Gen Suwa|first4=B.|last4=Asfaw|authorlink4=Berhane Asfaw|first5=T. D.|last5=White|authorlink5=Tim D. White|year=2011|title=Combining Prehension and Propulsion: The Foot of ''Ardipithecus ramidus''|journal=Science|volume=326|issue=5949|pages=72-72e8|doi=10.1126/science.1175832|pmid=19810198}}</ref> the big toe (though still capable of grasping) was used for pushing off, and the legs were aligned directly over the ankles instead of bowing out like in non-human great apes.<ref>{{cite journal|first=S. W.|last=Simpson|first2=N. E.|last2=Levin|first3=J.|last3=Quade|first4=M. J.|last4=Rogers|first5=S.|last5=Semaw|year=2019|title=''Ardipithecus ramidus'' postcrania from the Gona Project area, Afar Regional State, Ethiopia|journal=Journal of Human Evolution|volume=129|pages=1–45|doi=10.1016/j.jhevol.2018.12.005|pmid=30904038}}</ref>


==Paleobiology==
==Paleobiology==
The reduced canine size and reduced skull robustness in ''A. ramidus'' males (about the same size in males and females) is typically correlated with reduced male aggression, increased parental investment, and [[monogamy]].<ref name="AndThePaleobiology">{{cite journal |last=White |first=Tim D. |author2=Asfaw, Berhane|author3=Beyene, Yonas|author4=Haile-Selassie, Yohannes|author5=Lovejoy, C. Owen|author6=Suwa, Gen|author7=WoldeGabriel, Giday|author7-link=Giday WoldeGabriel|date=2009 |title=''Ardipithecus ramidus'' and the Paleobiology of Early Hominids |journal=[[Science (journal)|Science]] |volume=326 |issue=5949 |pages=75–86 |doi=10.1126/science.1175802 |pmid=19810190|bibcode = 2009Sci...326...64W |url=https://semanticscholar.org/paper/82b9e80c26a5f783c793b4e5c4b7e95e478abb21 }}</ref> Because of this, it is assumed that ''A. ramidus'' lived in a society similar to [[bonobo]]s and [[ateline]]s<ref name="Suwa_2009b"/> due to a process of [[self-domestication#in humans|self domestication]]. Because a similar process is thought to have occurred with the comparatively docile [[bonobo]]s from more aggressive chimps, ''A. ramidus'' society may have seen an increase in maternal care and female mate selection compared to its ancestors.<ref name="Clark & Henneberg 2015"/> Alternatively, it is possible that increased male size is a derived trait instead of basal (it evolved later rather than earlier), and is a specialized adaptation in modern great apes as a response to a different and more physically exerting lifestyle in males than females rather than being tied to aggression.<ref name=Lovejoy2009c>{{cite journal|first=C. O.|last=Lovejoy|year=2009|title=Reexamining Human Origins in Light of ''Ardipithecus ramidus''|journal=Science|volume=326|issue=5949|pages=74–74e8|doi=10.1126/science.1175834}}</ref>
The reduced canine size and reduced skull robustness in ''A. ramidus'' males (about the same size in males and females) is typically correlated with reduced male aggression, increased parental investment, and [[monogamy]].<ref name="AndThePaleobiology">{{cite journal |last=White |first=T. D.|authorlink=Tim D. White |last2=Asfaw|first2=B.|authorlink2=Berhane Asfaw|last3=Beyene|first3=Y.|last4=Haile-Selassie|first4=Y.|authorlink4=Yohannes Haile-Selassie|last5=Lovejoy|first5=C. O.|authorlink5=Owen Lovejoy (anthropologist)|last6=Suwa|first6=G.|authorlink6=Gen Suwa|last7=WoldeGabriel|first7= G.|author7-link=Giday WoldeGabriel|year=2009 |title=''Ardipithecus ramidus'' and the Paleobiology of Early Hominids |journal=[[Science (journal)|Science]] |volume=326 |issue=5949 |pages=75–86 |doi=10.1126/science.1175802 |pmid=19810190|bibcode = 2009Sci...326...64W |url=https://semanticscholar.org/paper/82b9e80c26a5f783c793b4e5c4b7e95e478abb21 }}</ref> Because of this, it is assumed that ''A. ramidus'' lived in a society similar to bonobos and [[ateline]] monkeys<ref name="Suwa_2009b"/> due to a process of [[self-domestication#in humans|self domestication]]. Because a similar process is thought to have occurred with the comparatively docile bonobos from more aggressive chimps, ''A. ramidus'' society may have seen an increase in maternal care and female mate selection compared to its ancestors.<ref name="Clark & Henneberg 2015"/> Alternatively, it is possible that increased male size is a derived trait instead of basal (it evolved later rather than earlier), and is a specialized adaptation in modern great apes as a response to a different and more physically exerting lifestyle in males than females rather than being tied to aggression.<ref name=Lovejoy2009c>{{cite journal|first=C. O.|last=Lovejoy|year=2009|title=Reexamining Human Origins in Light of ''Ardipithecus ramidus''|journal=Science|volume=326|issue=5949|pages=74–74e8|doi=10.1126/science.1175834}}</ref>


Such shortening of the skull—which may have caused a descension of the [[larynx]]—as well as lordosis—allowing better movement of the larynx—may have increased vocal ability potentially significantly pushing back the origins of language from the evolution of ''[[Homo]]''. It has been 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 argued that ''A. ramidus'' made use of more complex vocalizations, and vocalized at the same level as a human infant. 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 socio-neural behavioral adaptations.<ref>{{cite journal|first=G.|last=Clark|first2=M.|last2=Henneberg|year=2017|title=''Ardipithecus ramidus'' and the evolution of language and singing: An early origin for hominin vocal capability|journal=Homo|volume=68|issue=2|pages=101–121|doi=10.1016/j.jchb.2017.03.001}}</ref><ref name="Clark & Henneberg 2015">{{cite journal |doi=10.1515/anre-2015-0009 |title=The life history of Ardipithecus ramidus: A heterochronic model of sexual and social maturation |journal=Anthropological Review |volume=78 |issue=2 |page=109–132|year=2015 |last1=Clark |first1=Gary |last2=Henneberg |first2=Maciej }}</ref>
Such shortening of the skull—which may have caused a descension of the [[larynx]]—as well as lordosis—allowing better movement of the larynx—may have increased vocal ability, potentially significantly pushing back the [[origin of language]] to well before the evolution of ''Homo''. It has been 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 argued that ''A. ramidus'' made use of more complex vocalizations, and vocalized at the same level as a human infant. 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 socio-neural behavioral adaptations.<ref>{{cite journal|first=G.|last=Clark|first2=M.|last2=Henneberg|year=2017|title=''Ardipithecus ramidus'' and the evolution of language and singing: An early origin for hominin vocal capability|journal=Homo|volume=68|issue=2|pages=101–121|doi=10.1016/j.jchb.2017.03.001}}</ref><ref name="Clark & Henneberg 2015">{{cite journal |doi=10.1515/anre-2015-0009 |title=The life history of Ardipithecus ramidus: A heterochronic model of sexual and social maturation |journal=Anthropological Review |volume=78 |issue=2 |page=109–132|year=2015 |last1=Clark |first1=Gary |last2=Henneberg |first2=Maciej }}</ref>


[[File:Nut cracking Ardipithecus.png|thumb|left|Hypothetical restoration of an ''Ardipithecus'' using a hammer and anvil to crack open a nut]]
The teeth of ''A. ramidus'' indicate that it was likely a generalized [[omnivore]] and [[frugivore|fruit eater]] which predominantly consumed [[C3 plant]]s in [[woodland]]s or [[gallery forest]]s. The teeth lacked adaptations for abrasive foods.<ref name="Suwa_2009b"/><ref name="AndThePaleobiology"/><ref name=Sarmiento2011/> American primatologist [[Craig Stanford]] postulated that ''Ardipithecus'' behaved similarly to chimps, which, if the case, would mean it consumed meat opportunistically, and captured prey with its hands.<ref>{{cite journal|first=C. B.|last=Stanford|authorlink=Craig Stanford|year=2012|title=Chimpanzees and the Behavior of ''Ardipithecus ramidus''|journal=Annual Review of Anthropology|volume=41|pages=139–149|doi=10.1146/annurev-anthro-092611-145724|url=https://doi.org/10.1146/annurev-anthro-092611-145724}}</ref> Lacking the speed and agility of chimps and baboons, meat intake would have been sourced from only what could have been captured by limited pursuit, or from scavenging carcasses.<ref>{{cite journal|first=K.|last=Sayers|first2=C. O.|last2=Lovejoy|authorlink2=Owen Lovejoy (anthropologist)|year=2014|title=Blood, Bulbs, and Bunodonts: On Evolutionary Ecology and the Diets of ''Ardipithecus'', ''Australopithecus'', and Early ''Homo''|journal=Quarterly Review of Biology|volume=89|issue=4|pages=319–357|pmc=4350785|pmid=25510078}}</ref>
The teeth of ''A. ramidus'' indicate that it was likely a generalized [[omnivore]] and [[frugivore|fruit eater]] which predominantly consumed [[C3 plant]]s in woodlands or [[gallery forest]]s. The teeth lacked adaptations for abrasive foods.<ref name="Suwa_2009b"/><ref name="AndThePaleobiology"/><ref name=Sarmiento2011/> American primatologist [[Craig Stanford]] postulated that ''Ardipithecus'' behaved similarly to chimps, which, if the case, would mean it consumed meat opportunistically, and captured prey with its hands. Chimps are also the most [[tool use by animals|technologically advanced non-human]], and have at least 37 identified traditions across their geographical range.<ref>{{cite journal|first=C. B.|last=Stanford|authorlink=Craig Stanford|year=2012|title=Chimpanzees and the Behavior of ''Ardipithecus ramidus''|journal=Annual Review of Anthropology|volume=41|pages=139–149|doi=10.1146/annurev-anthro-092611-145724|url=https://doi.org/10.1146/annurev-anthro-092611-145724}}</ref> Lacking the speed and agility of chimps and baboons, meat intake by ''Ardipithecus'' would have been sourced from only what could have been captured by limited pursuit, or from scavenging carcasses.<ref>{{cite journal|first=K.|last=Sayers|first2=C. O.|last2=Lovejoy|authorlink2=Owen Lovejoy (anthropologist)|year=2014|title=Blood, Bulbs, and Bunodonts: On Evolutionary Ecology and the Diets of ''Ardipithecus'', ''Australopithecus'', and Early ''Homo''|journal=Quarterly Review of Biology|volume=89|issue=4|pages=319–357|pmc=4350785|pmid=25510078}}</ref>


==Paleoecology==
==Paleoecology==
Line 86: Line 88:
The Geological, Isotopic, Botanical, Invertebrate, and Lower Vertebrate Surroundings of ''Ardipithecus ramidus''|journal=Science|volume=326|issue=5949|pages=65–65e5|doi=10.1126/science.1175817}}</ref> Conversely, annual precipitation at Aramis was calculated to have been {{cvt|1500|mm}}, which is seen in some of the hottest, driest parts of East Africa.<ref name=Cerling2010/>
The Geological, Isotopic, Botanical, Invertebrate, and Lower Vertebrate Surroundings of ''Ardipithecus ramidus''|journal=Science|volume=326|issue=5949|pages=65–65e5|doi=10.1126/science.1175817}}</ref> Conversely, annual precipitation at Aramis was calculated to have been {{cvt|1500|mm}}, which is seen in some of the hottest, driest parts of East Africa.<ref name=Cerling2010/>


[[Carbon isotope]] analyses of the herbivore teeth from Gona associated with ''A. ramidus'' indicate that these herbivores fed mainly on [[C4 plants]] and grasses rather than forest plants. The area seems to have featured [[bushland]] and grasslands.<ref>{{cite book|first=N. E.|last=Levin|first2=S. W.|last2=Simpson|first3=J.|last3=Quade|first4=T. E.|last4=Cerling|first5=S. R.|last5=Frost|year=2008|chapter=Herbivore enamel carbon isotopic composition and the environmental context of ''Ardipithecus'' at Gona, Ethiopia|title=The Geology of Early Humans in the Horn of Africa|publisher=Geological Society of America Special Paper|volume=446|pages=215–234|doi=10.1130/2008.2446(10)}}</ref>
[[Carbon isotope]] analyses of the herbivore teeth from the Gona Western Margin associated with ''A. ramidus'' indicate that these herbivores fed mainly on [[C4 plants]] and grasses rather than forest plants. The area seems to have featured [[bushland]] and grasslands.<ref>{{cite book|first=N. E.|last=Levin|first2=S. W.|last2=Simpson|first3=J.|last3=Quade|first4=T. E.|last4=Cerling|first5=S. R.|last5=Frost|year=2008|chapter=Herbivore enamel carbon isotopic composition and the environmental context of ''Ardipithecus'' at Gona, Ethiopia|title=The Geology of Early Humans in the Horn of Africa|publisher=Geological Society of America Special Paper|volume=446|pages=215–234|doi=10.1130/2008.2446(10)}}</ref>


== See also ==
== See also ==

Revision as of 06:35, 29 January 2020

Ardipithecus ramidus
Temporal range: Zanclean 4.5–4.32 Ma
↓
A skull
A. ramidus at the Museo Nacional de Ciencias Naturales
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Hominidae
Subfamily: Homininae
Tribe: Hominini
Genus: †Ardipithecus
Species:
†A. ramidus
Binomial name
†Ardipithecus ramidus
(White, Suwa & Asfaw, 1994)

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 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 chimps, orangutans, and gorillas to being a creature without a modern anatomical cognate.

The facial anatomy suggests that A. ramidus males were less aggressive than those of modern chimps, which is correlated to increased parental care and monogamy in primates. It has also been suggested that it was among the earliest of human ancestors to use some proto-language, possibly capable of vocalizing at the same level as a human infant. A. ramidus appears to have inhabited woodland and bushland corridors between savannas.

Taxonomy

Map showing discovery locations of various australopithecines

The first remains were described in 1994 by American anthropologist Tim D. White, Japanese paleoanthropologist Gen Suwa, and Ethiopian paleontologist Berhane Asfaw. The holotype specimen, ARA-VP-6/1, comprised an associated set of 10 teeth; and there were 16 other paratypes identified, preserving also skull and arm fragments. These were unearthed in the 4.4 million year (Ma) deposits of the Afar region in Aramis, Ethiopia from 1992 to 1993. They classified it as Australopithecus ramidus, the species name deriving from the Afar language ramid "root". In 1995, they made a corrigendum, recommending the species be split off into a separate genus from Australopithecus.[1] Ardipithecus stems from Afar ardi "ground" and Ancient Greek pithecus "ape".

Fossils from at least nine A. ramidus individuals at As Duma, Gona Western Margin, Afar, were unearthed from 1993–2003. The fossils were dated to between 4.32 and 4.51 million years ago.[2]

In 2001, 6.5–5.5 million year old fossils from the Middle Awash were classified as a subspecies of A. ramidus by Ethiopian paleoanthropologist Yohannes Haile-Selassie.[3] In 2004, Haile-Selassie, Suwa, and White split it off into its own species, A. kadabba.[4]

In 2009, White and colleagues reaffirmed the position of Ardipithecus as a hominin more closely related to modern humans than to chimps based on dental similarity, a short base of the skull, and adaptations to bipedality.[5] In 2011, primatologist Esteban Sarmiento said that there is not enough evidence to assign Ardipithecus to Hominini,[6] but its closer affinities to Homo than chimps have been reaffirmed in following years.[7][8]

Evolutionary tree according to a 2019 study:[9]

Hominini
"Ardi", the most complete Ardipithecus specimen

Before the discovery of Ardipithecus and other pre-Australopithecus hominins, it was assumed that the chimpanzee–human last common ancestor and preceding apes appeared much like modern day chimps, orangutans, and gorillas, which would have meant these three changed very little over millions of years. Their discovery led to the postulation that modern great apes, much like humans, evolved several specialized adaptations to their environment (have highly derived morphologies), and their ancestors were comparatively poorly adapted to suspensory behavior or knuckle walking, and did not have such a specialized diet. Also, the origins of bipedality were thought to have occurred due to a switch from a forest to a savanna environment, but the presence of bipedal pre-Australopithecus hominins in woodlands has called this into question,[10] though they inhabited wooded corridors near or between savannas.[11] It is also possible that Ardipithecus and pre-Australopithecus were random offshoots of the hominin line.

Description

One of the larger specimens from Aramis, ARA-VP-6/500, was estimated to have stood 124 cm (4 ft 1 in) and weighed 51 kg (112 lb) based on comparisons with large-bodied female apes. Another specimen, A.L. 288-1, was estimated to have weighed 26 kg (57 lb). Assuming subsistence was primarily sourced from climbing in trees, A. ramidus may not have exceeded 35–60 kg (77–132 lb).[12]

A. ramidus had a small brain, measuring 300–350 cc (18–21 cu in). This is slightly smaller than a modern bonobo or chimp brain, but much smaller than the brain of Australopithecus–about 400–550 cc (24–34 cu in)–and roughly 20% the size of the modern human brain. Like chimps, the A. ramidus face was much more pronounced (prognathic) than modern humans.[13] The size of the upper canine tooth in A. ramidus males was not distinctly different from that of females, in contrast to the sexual dimorphism observed in chimps where males have significantly larger and sharper upper canines than females.[14]

Reconstruction of Ardipithecus skeleton

A. ramidus feet are better suited for walking than chimps. However, like non-human great apes, but unlike all previously recognized human ancestors, it had a grasping big toe adapted for locomotion in the trees (an arboreal lifestyle), though it was likely not as specialized for grasping as it is in modern great apes.[15][5] Its tibial and tarsal lengths indicate a leaping ability similar to bonobos.[6] It lacks any characters suggestive of specialized suspension, vertical climbing, or knuckle walking; and it seems to have used a method of locomotion unlike any modern great ape, which combined arboreal palm walking clambering and a form of bipedality more primitive than Australopithecus. The discovery of such unspecialized locomotion led American anthropologist Owen Lovejoy and colleagues to postulate that the chimpanzee–human last common ancestor used a similar method of locomotion.[16][5]

The upper pelvis (distance from the sacrum to the hip joint) is shorter than in any known ape. It is inferred to have had a long lumbar vertebral series, and lordosis (human curvature of the spine), which are adaptations for bipedality. However, the legs were not completely aligned with the torso (were anterolaterally displaced), and Ardipithecus may have relied more on its quadriceps than hamstrings for walking (the opposite is true for modern humans).[17] However, it lacked foot arches and had to adopt a flat-footed stance. These would have made it less efficient at walking and running than Australopithecus and Homo. It may not have employed a bipedal gait for very long time intervals.[8] It may have predominantly used palm walking on the ground,[18] Nonetheless, A. ramidus still had specialized adaptations for bipedality, such as a robust fibularis longus muscle used in pushing the foot off the ground while walking (plantarflexion),[15] the big toe (though still capable of grasping) was used for pushing off, and the legs were aligned directly over the ankles instead of bowing out like in non-human great apes.[19]

Paleobiology

The reduced canine size and reduced skull robustness in A. ramidus males (about the same size in males and females) is typically correlated with reduced male aggression, increased parental investment, and monogamy.[5] Because of this, it is assumed that A. ramidus lived in a society similar to bonobos and ateline monkeys[14] due to a process of self domestication. Because a similar process is thought to have occurred with the comparatively docile bonobos from more aggressive chimps, A. ramidus society may have seen an increase in maternal care and female mate selection compared to its ancestors.[20] Alternatively, it is possible that increased male size is a derived trait instead of basal (it evolved later rather than earlier), and is a specialized adaptation in modern great apes as a response to a different and more physically exerting lifestyle in males than females rather than being tied to aggression.[10]

Such shortening of the skull—which may have caused a descension of the larynx—as well as lordosis—allowing better movement of the larynx—may have increased vocal ability, potentially significantly pushing back the origin of language to well before the evolution of Homo. It has been 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 argued that A. ramidus made use of more complex vocalizations, and vocalized at the same level as a human infant. 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 socio-neural behavioral adaptations.[21][20]

Hypothetical restoration of an Ardipithecus using a hammer and anvil to crack open a nut

The teeth of A. ramidus indicate that it was likely a generalized omnivore and fruit eater which predominantly consumed C3 plants in woodlands or gallery forests. The teeth lacked adaptations for abrasive foods.[14][5][6] American primatologist Craig Stanford postulated that Ardipithecus behaved similarly to chimps, which, if the case, would mean it consumed meat opportunistically, and captured prey with its hands. Chimps are also the most technologically advanced non-human, and have at least 37 identified traditions across their geographical range.[22] Lacking the speed and agility of chimps and baboons, meat intake by Ardipithecus would have been sourced from only what could have been captured by limited pursuit, or from scavenging carcasses.[23]

Paleoecology

Half of the large mammal species associated with A. ramidus at Aramis are spiral-horned antelope and colobine monkeys (namely Kuseracolobus and Pliopapio). There are a few specimens of primitive white and black rhino species, and elephants, giraffes, and hippo specimens are less abundant. These animals indicate that Aramis ranged from wooded grasslands to forests, but A. ramidus likely preferred the closed habitats,[24] specifically riverine areas as such water sources may have supported more canopy coverage.[25] Aramis as a whole generally had less than 25% canopy cover.[11] There were exceedingly high rates of scavenging, indicating a highly competitive environment somewhat like Ngorongoro Crater. Predators of the area were the hyenas Ikelohyaena abronia and Crocuta dietrichi, the bear Agriotherium, the dog Eucyon, and crocodiles.[26] Bayberry, hackberry, and palm trees appear to have been common at the time from Aramis to the Gulf of Aden; and botanical evidence suggests a cool, humid climate.[27] Conversely, annual precipitation at Aramis was calculated to have been 1,500 mm (59 in), which is seen in some of the hottest, driest parts of East Africa.[11]

Carbon isotope analyses of the herbivore teeth from the Gona Western Margin associated with A. ramidus indicate that these herbivores fed mainly on C4 plants and grasses rather than forest plants. The area seems to have featured bushland and grasslands.[28]

See also

References

  1. ^ White, T. D.; Suwa, G.; Asfaw, B. (1994). "Australopithecus ramidus, a new species of early hominid from Aramis, Ethiopia" (PDF). Nature. 371 (6495): 306–312. Bibcode:1994Natur.371..306W. doi:10.1038/371306a0. PMID 8090200. Archived from the original (PDF) on 2013-04-13.
  2. ^ Semaw, S.; Simpson, S. W.; et al. (2005). "Early Pliocene hominids from Gona, Ethiopia". Nature. 433 (7023): 301–305. doi:10.1038/nature03177. PMID 15662421.
  3. ^ Haile-Selassie, Y. (2001). "Late Miocene hominids from the Middle Awash, Ethiopia". Nature. 42 (6843): 179–181. doi:10.1038/35084063. PMID 11449272.
  4. ^ Haile-Selassie, Y.; Suwa, G.; White, T. D. (2004). "Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution". Science. 303 (5663): 1503–1505. Bibcode:2004Sci...303.1503H. doi:10.1126/science.1092978. PMID 15001775.
  5. ^ a b c d e 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...64W. doi:10.1126/science.1175802. PMID 19810190.
  6. ^ a b c 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.
  7. ^ 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): 948–953. doi:10.1073/pnas.1322639111. PMC 3903226. PMID 24395771.
  8. ^ a b White, T. D.; Lovejoy, C. O.; Asfaw, B.; Carlson, J. P.; Suwa, G. (2015). "Neither chimpanzee nor human, Ardipithecus reveals the surprising ancestry of both". Proceedings of the National Academy of Sciences. 112 (16): 4877–4884. doi:10.1073/pnas.1403659111. PMC 4413341. PMID 25901308.
  9. ^ 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.
  10. ^ a b Lovejoy, C. O. (2009). "Reexamining Human Origins in Light of Ardipithecus ramidus". Science. 326 (5949): 74–74e8. doi:10.1126/science.1175834.
  11. ^ a b c Cerling, T. E.; Levin, N. E.; Quade, J. (2010). "Comment on the Paleoenvironment of Ardipithecus ramidus". Science. 328 (5982): 1105. doi:10.1126/science.1185274.
  12. ^ Lovejoy, C. O.; Suwa, G.; Simpson, S. W.; Matternes, J. H.; White, T. D. (2009). "The Great Divides: Ardipithecus ramidus Reveals the Postcrania of Our Last Common Ancestors with African Apes". Science. 326 (5949): 73–106. doi:10.1126/science.1175833.
  13. ^ Suwa, G.; Asfaw, B.; Kono, R. T.; Kubo, D.; Lovejoy, C. O.; White, T. D.; et al. (2009). "The Ardipithecus ramidus skull and its implications for hominid origins" (PDF). Science. 326 (5949): 68, 68e1–68e7. Bibcode:2009Sci...326...68S. doi:10.1126/science.1175825. PMID 19810194.
  14. ^ a b c Suwa, G.; Kono, R. T.; Simpson, S. W.; Asfaw, B.; Lovejoy, C. O.; White, T. D.; et al. (2009). "Paleobiological implications of the Ardipithecus ramidus dentition" (PDF). Science. 326 (5949): 69, 94–99. Bibcode:2009Sci...326...94S. doi:10.1126/science.1175824. PMID 19810195.
  15. ^ a b Lovejoy, C. O.; Latimar, B.; Suwa, G.; Asfaw, B.; White, T. D. (2011). "Combining Prehension and Propulsion: The Foot of Ardipithecus ramidus". Science. 326 (5949): 72-72e8. doi:10.1126/science.1175832. PMID 19810198.
  16. ^ Lovejoy, C. O.; Simpson, S. W.; White, T. D.; Asfaw, B.; Suwa, G. (2009). "Careful Climbing in the Miocene: The Forelimbs of Ardipithecus ramidus and Humans Are Primitive". Science. 326 (5949): 70–70e8. doi:10.1126/science.1175827.
  17. ^ Lovejoy, C. O.; Suwa, G.; Spurlock, L.; Asfaw, B.; White, T. D. (2009). "The Pelvis and Femur of Ardipithecus ramidus: The Emergence of Upright Walking". Science. 326 (5949): 71–71e6. doi:10.1126/science.1175831. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  18. ^ Prang, T. C. (2019). "The African ape-like foot of Ardipithecus ramidus and its implications for the origin of bipedalism". eLife. 8: e44433. doi:10.7554/eLife.44433. PMC 6491036. PMID 31038121.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  19. ^ Simpson, S. W.; Levin, N. E.; Quade, J.; Rogers, M. J.; Semaw, S. (2019). "Ardipithecus ramidus postcrania from the Gona Project area, Afar Regional State, Ethiopia". Journal of Human Evolution. 129: 1–45. doi:10.1016/j.jhevol.2018.12.005. PMID 30904038.
  20. ^ a b 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.
  21. ^ 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.
  22. ^ Stanford, C. B. (2012). "Chimpanzees and the Behavior of Ardipithecus ramidus". Annual Review of Anthropology. 41: 139–149. doi:10.1146/annurev-anthro-092611-145724.
  23. ^ Sayers, K.; Lovejoy, C. O. (2014). "Blood, Bulbs, and Bunodonts: On Evolutionary Ecology and the Diets of Ardipithecus, Australopithecus, and Early Homo". Quarterly Review of Biology. 89 (4): 319–357. PMC 4350785. PMID 25510078.
  24. ^ White, T. D.; et al. (2009). "Macrovertebrate Paleontology and the Pliocene Habitat of Ardipithecus ramidus" (PDF). Science. 326 (5949): 67–93. doi:10.1126/science.1175822.
  25. ^ Gani, M. R.; Gani, N. D. (2011). "River-margin habitat of Ardipithecus ramidus at Aramis, Ethiopia 4.4 million years ago". Nature Communications. 2: 602. doi:10.1038/ncomms1610. PMID 22186898.
  26. ^ Louchart, A.; Wesselman, H.; Blumenschine, R. J.; et al. (2009). "Taphonomic, Avian, and Small-Vertebrate Indicators of Ardipithecus ramidus Habitat". Science. 326 (5949): 66–66e4. doi:10.1126/science.1175823.
  27. ^ WoldeGabriel, G.; Ambrose, S. H.; Barboni, D.; et al. (2009). "The Geological, Isotopic, Botanical, Invertebrate, and Lower Vertebrate Surroundings of Ardipithecus ramidus". Science. 326 (5949): 65–65e5. doi:10.1126/science.1175817.
  28. ^ Levin, N. E.; Simpson, S. W.; Quade, J.; Cerling, T. E.; Frost, S. R. (2008). "Herbivore enamel carbon isotopic composition and the environmental context of Ardipithecus at Gona, Ethiopia". The Geology of Early Humans in the Horn of Africa. Vol. 446. Geological Society of America Special Paper. pp. 215–234. doi:10.1130/2008.2446(10).

External links

Wikispecies has information related to Ardipithecus ramidus.
Wikimedia Commons has media related to Ardipithecus ramidus.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Ardipithecus_ramidus&oldid=938119522"