Difference between revisions of "Hominin" - New World Encyclopedia
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Primate classification has undergone many revisions over the years, from the 1960s when humans were the only extant species in the family Hominidae until today, when it is common to place [[chimpanzee]]s, [[gorilla]]s, and [[orangutan]]s in Hominidae as well. (There are other taxonomic schemes, such as placing extant and extinct chimpanzees and gorillas in the family Panidae, orangutans in the historical group Pongidae, and humans in Hominidae). | Primate classification has undergone many revisions over the years, from the 1960s when humans were the only extant species in the family Hominidae until today, when it is common to place [[chimpanzee]]s, [[gorilla]]s, and [[orangutan]]s in Hominidae as well. (There are other taxonomic schemes, such as placing extant and extinct chimpanzees and gorillas in the family Panidae, orangutans in the historical group Pongidae, and humans in Hominidae). | ||
| − | The creation of the taxon Hominini is the result of the current idea that the least similar species of a trichotomy should be separated from the other two. Thus, orangutans are separated into the subfamily Ponginae while the other great apes are placed in subfamily Homininae, and | + | The creation of the taxon Hominini is the result of the current idea that the least similar species of a trichotomy should be separated from the other two. Thus, orangutans are separated into the subfamily Ponginae while the other great apes are placed in subfamily Homininae. By various methods ([[protein]] differences, [[DNA]] differences, etc.), it is determined that the branching point between humans and chimpanzees is more recent than between chimpanzees and gorillas, and thus suggesting that chimpanzees are our nearest relatives (Mayr 2001)). Thus, the gorillas are separated into tribe Gorillini, while extant and extinct humans and chimpanzees are placed in tribe Hominini. |
[[Image:Hominini.PNG|left|frame|[[Extant]] Hominoid family tree]] | [[Image:Hominini.PNG|left|frame|[[Extant]] Hominoid family tree]] | ||
| − | The anatomical and biochemical similarity between chimpanzees and humans is | + | The anatomical and biochemical similarity between chimpanzees and humans is indeed striking. Various studies show that they have about 95 to 99.4 percent of their [[DNA]] in common (Wildman 2003). For example, comparisons between chimpanzees and humans in terms of [[protein]] sequences, [[allele]] differences, and DNA heteroduplex melting points show more than 98 percent identity (King and Wilson 1975; Wood 2006). Ebersberger et al. (2002) found a difference of only 1.24 percent when he aligned 1.9 million [[nucleotide]]s of chimpanzee DNA and compared them with the corresponding human sequences in the human genome (Wood 2006). Using a 4.97 million nucleotide portion of DNA from human chromosome 7 and comparing to chimpanzee orthologies yielded only 1.13 percent mismatches (Liu et al. 2003). Other biochemical comparisions can be seen in the article on [[chimpanzee#chimpanzees and humans|chimpanzees]]. |
| − | + | In the 1996 proposal of Mann and Weiss, the tribe Hominini includes ''Pan'' as well as ''[Homo (genus)|Homo]]'' as separate subtribes. Homo, and, by inference, all bipedal apes, is by itself only in the subtribe Hominina, while Pan is in the Panina subtribe. | |
Chimpanzees are so similar to humans that some scientists have proposed that the two chimpanzee species, ''troglodytes'' and ''paniscus'', belong with ''sapiens'' in the genus ''[[Homo (genus)|Homo]]'', rather than in ''Pan''. | Chimpanzees are so similar to humans that some scientists have proposed that the two chimpanzee species, ''troglodytes'' and ''paniscus'', belong with ''sapiens'' in the genus ''[[Homo (genus)|Homo]]'', rather than in ''Pan''. | ||
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==Pan/Homo split== | ==Pan/Homo split== | ||
| − | + | Through a study of proteins, comparison of [[DNA]], and use of a molecular clock (a method of calculating evolution based on the speed at which genes mutate), scientists believe the''Pan/Homo'' split happened about 5 to 8 million years ago (Mayr 2001, Physorg 2005). One study, utilizing 167 nuclear protein-coding genes, showed the split to be roughly 5 to 7 million years ago (Kumar et al. 2005), while another analysis, utilizing 20 million aligned base pairs, reveals that human–chimpanzee [[speciation]] occurred less than 6.3 million years ago and probably more recently, such as 5.4 mya (Patterson et al. 2006). This later study compared key sequences of genes rather than look at average genetic differences between human and chimp. Interestingly, this later study claims that study of chromosome X shows features that could best be explained if the chimpanzee and human lineages initially diverged, but then later exchanged genes before final separation. | |
| − | + | Kumar et al. (2005) note that hypothesis "about the timing of human-chimpanzee divergence demand more precise fossil-based calibrations." However, it is interesting to note that no fossil species on the ''Pan'' side of the split have been determined; all of the extinct genera are ancestral to ''Homo'', or are offshoots of such. However, both ''[[Orrorin]]*'' and ''[[Sahelanthropus]]*'' existed around the time of the split, and so may be ancestral to both humans and chimpanzees. | |
| − | + | In 2002, a 6–7 million year old [[fossil]] skull nicknamed "Toumaï" by its discoverers, and formally classified as ''[[Sahelanthropus tchadensis]]*'', was discovered in [[Chad]] and is possibly the earliest hominid [[fossil]] ever found. In addition to its age, Toumaï, unlike the 3–4 million year younger gracile [[australopithecine]] dubbed "[[Australopithecus afarensis|Lucy]]*", has a relatively flat face without the prominent snout seen on other pre-''[[Homo (genus)|Homo]]'' hominids. Some researchers have made the suggestion that this previously unknown species may in fact be a direct ancestor of modern humans (or at least closely related to a direct ancestor). Others contend that one fossil is not enough to make such a claim because it would overturn the conclusions of over 100 years of [[anthropology|anthropological]] study. While some scientists claim that it is merely the skull of a female gorilla, others have called it the most important hominin fossil since ''Australopithecus''. | |
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| − | + | ==See also== | |
| + | *[[Chimpanzee]] | ||
| + | *[[Human evolution]] | ||
| + | *[[Hominidae]] | ||
| + | *[[Hominoidea]] | ||
| + | <br clear="all" /> | ||
| − | == | + | ==References== |
| + | {{references-small}} | ||
| − | + | ref name=Mann>{{cite journal | author = Mann, Alan and Mark Weiss | year = 1996 | title = Hominoid Phylogeny and Taxonomy: a consideration of the molecular and Fossil Evidence in an Historical Perspective | journal = Molecular Phylogenetics and Evolution | volume = 5 | issue = 1 | pages = 169-181}}</ref> | |
| − | + | Nature 441, 1103-1108 (29 June 2006) | doi:10.1038/nature04789; Received 5 November 2005; Accepted 7 April 2006; Published online 17 May 2006 | |
| + | Genetic evidence for complex speciation of humans and chimpanzees | ||
| + | Nick Patterson1, Daniel J. Richter1, Sante Gnerre1, Eric S. Lander1,2 and David Reich1,3 | ||
| + | <Physorg.com 2005. ref name=split> {{cite web | url = http://www.physorg.com/news9211.html | title = Scientists narrow time limits for human, chimp split | accessdate = 2005-12-21 | data = 2005-12-20 | work = [http://www.physorg.com PhysOrg.com]}}</ref> | ||
| + | Published online before print December 19, 2005, 10.1073/pnas.0509585102 OPEN ACCESS ARTICLE | ||
| + | PUblication of the National Academy of Sciences PNAS Anthropology-Biological Sciences | ||
| + | Placing confidence limits on the molecular age of the human-chimpanzee divergence | ||
| + | ( Bayesian analysis | molecular clock | hominid | fossil | primate ) | ||
| + | Sudhir Kumar *, Alan Filipski *, Vinod Swarna *, Alan Walker ¶||**, and S. Blair Hedges ¶ | ||
| + | Mayr, E. 2001. | ||
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* Ebersberger, I., D. Metzler, C. Schwarz, and S. Paabo. 2002. Genomewide comparison of DNA sequences between humans and chimpanzees. ''American Journal of Human Genetics'' 70:1490–97. | * Ebersberger, I., D. Metzler, C. Schwarz, and S. Paabo. 2002. Genomewide comparison of DNA sequences between humans and chimpanzees. ''American Journal of Human Genetics'' 70:1490–97. | ||
Revision as of 16:52, 10 March 2007
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Subtribe Panina Subtribe Hominina
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- For an explanation of very similar terms see Hominid.
Hominin is any member of the primate tribe Hominini, a classification that generally is considered to include only humans (genus Homo), chimpanzees (Pan), and their extinct ancestors. In recent classifications, Hominini is a tribe of the subfamily Homininae (humans, chimpanzees, gorillas) of the family Hominidae (humans, chimpanzees, gorillas, and orangutans).
Unification aspects: chimpanzees and humans are placed together because of their remarkable genetic similarities. For example (from chimp article). But also note: (note differences)
Overview of Hominini classification
Primate classification has undergone many revisions over the years, from the 1960s when humans were the only extant species in the family Hominidae until today, when it is common to place chimpanzees, gorillas, and orangutans in Hominidae as well. (There are other taxonomic schemes, such as placing extant and extinct chimpanzees and gorillas in the family Panidae, orangutans in the historical group Pongidae, and humans in Hominidae).
The creation of the taxon Hominini is the result of the current idea that the least similar species of a trichotomy should be separated from the other two. Thus, orangutans are separated into the subfamily Ponginae while the other great apes are placed in subfamily Homininae. By various methods (protein differences, DNA differences, etc.), it is determined that the branching point between humans and chimpanzees is more recent than between chimpanzees and gorillas, and thus suggesting that chimpanzees are our nearest relatives (Mayr 2001)). Thus, the gorillas are separated into tribe Gorillini, while extant and extinct humans and chimpanzees are placed in tribe Hominini.
The anatomical and biochemical similarity between chimpanzees and humans is indeed striking. Various studies show that they have about 95 to 99.4 percent of their DNA in common (Wildman 2003). For example, comparisons between chimpanzees and humans in terms of protein sequences, allele differences, and DNA heteroduplex melting points show more than 98 percent identity (King and Wilson 1975; Wood 2006). Ebersberger et al. (2002) found a difference of only 1.24 percent when he aligned 1.9 million nucleotides of chimpanzee DNA and compared them with the corresponding human sequences in the human genome (Wood 2006). Using a 4.97 million nucleotide portion of DNA from human chromosome 7 and comparing to chimpanzee orthologies yielded only 1.13 percent mismatches (Liu et al. 2003). Other biochemical comparisions can be seen in the article on chimpanzees.
In the 1996 proposal of Mann and Weiss, the tribe Hominini includes Pan as well as [Homo (genus)|Homo]] as separate subtribes. Homo, and, by inference, all bipedal apes, is by itself only in the subtribe Hominina, while Pan is in the Panina subtribe.
Chimpanzees are so similar to humans that some scientists have proposed that the two chimpanzee species, troglodytes and paniscus, belong with sapiens in the genus Homo, rather than in Pan.
Pan/Homo split
Through a study of proteins, comparison of DNA, and use of a molecular clock (a method of calculating evolution based on the speed at which genes mutate), scientists believe thePan/Homo split happened about 5 to 8 million years ago (Mayr 2001, Physorg 2005). One study, utilizing 167 nuclear protein-coding genes, showed the split to be roughly 5 to 7 million years ago (Kumar et al. 2005), while another analysis, utilizing 20 million aligned base pairs, reveals that human–chimpanzee speciation occurred less than 6.3 million years ago and probably more recently, such as 5.4 mya (Patterson et al. 2006). This later study compared key sequences of genes rather than look at average genetic differences between human and chimp. Interestingly, this later study claims that study of chromosome X shows features that could best be explained if the chimpanzee and human lineages initially diverged, but then later exchanged genes before final separation.
Kumar et al. (2005) note that hypothesis "about the timing of human-chimpanzee divergence demand more precise fossil-based calibrations." However, it is interesting to note that no fossil species on the Pan side of the split have been determined; all of the extinct genera are ancestral to Homo, or are offshoots of such. However, both Orrorin and Sahelanthropus existed around the time of the split, and so may be ancestral to both humans and chimpanzees.
In 2002, a 6–7 million year old fossil skull nicknamed "Toumaï" by its discoverers, and formally classified as Sahelanthropus tchadensis, was discovered in Chad and is possibly the earliest hominid fossil ever found. In addition to its age, Toumaï, unlike the 3–4 million year younger gracile australopithecine dubbed "Lucy", has a relatively flat face without the prominent snout seen on other pre-Homo hominids. Some researchers have made the suggestion that this previously unknown species may in fact be a direct ancestor of modern humans (or at least closely related to a direct ancestor). Others contend that one fossil is not enough to make such a claim because it would overturn the conclusions of over 100 years of anthropological study. While some scientists claim that it is merely the skull of a female gorilla, others have called it the most important hominin fossil since Australopithecus.
See also
ReferencesISBN links support NWE through referral fees
ref name=Mann>Mann, Alan and Mark Weiss (1996). Hominoid Phylogeny and Taxonomy: a consideration of the molecular and Fossil Evidence in an Historical Perspective. Molecular Phylogenetics and Evolution 5 (1): 169-181.</ref>
Nature 441, 1103-1108 (29 June 2006) | doi:10.1038/nature04789; Received 5 November 2005; Accepted 7 April 2006; Published online 17 May 2006 Genetic evidence for complex speciation of humans and chimpanzees Nick Patterson1, Daniel J. Richter1, Sante Gnerre1, Eric S. Lander1,2 and David Reich1,3
<Physorg.com 2005. ref name=split> Scientists narrow time limits for human, chimp split. PhysOrg.com. Retrieved 2005-12-21.</ref>
Published online before print December 19, 2005, 10.1073/pnas.0509585102 OPEN ACCESS ARTICLE
PUblication of the National Academy of Sciences PNAS Anthropology-Biological Sciences Placing confidence limits on the molecular age of the human-chimpanzee divergence ( Bayesian analysis | molecular clock | hominid | fossil | primate )
Sudhir Kumar *, Alan Filipski *, Vinod Swarna *, Alan Walker ¶||**, and S. Blair Hedges ¶
Mayr, E. 2001.
- Ebersberger, I., D. Metzler, C. Schwarz, and S. Paabo. 2002. Genomewide comparison of DNA sequences between humans and chimpanzees. American Journal of Human Genetics 70:1490–97.
King, M.C. and A.C. Wilson (1975). Evolution at two levels in Humans and Chimpanzees. Science 188: 107-116
- Liu, G., NISC Comparative Sequencing Program, S. Zhao, J. A. Bailey, S. C. Sahinalp, C. Alkan, E. Tuzun, E. D. Green, and E. E. Eichler. 2003. Analysis of primate genomic variation reveals a repeat-driven expansion of the human genome. Genome Research 13:358–68.
- Wildman, D. E., M. Uddin, G. Liu, L. I. Grossman, and M. Goodman. 2003. Implications of natural selection in shaping 99.4% nonsynonymous DNA identity between humans and chimpanzees: Enlarging genus Homo. Proceedings of the National Academy of Sciences 100:7181–88.
- Wood, T. C. 2006. The chimpanzee genome and the problem of biological similarity. Occassional Papers of the BSG 7:1–18.
Sahelanthropus tchadensis • Orrorin tugenensis • Ardipithecus
Australopithecus: A. anamensis • A. afarensis • A. bahrelghazali • A. africanus • A. garhi
Paranthropus: P. aethiopicus • P. boisei • P. robustus
Kenyanthropus platyops
Homo: H. habilis • H. rudolfensis • H. georgicus • H. ergaster • H. erectus (H. e. lantianensis • H. e. palaeojavanicus • H. e. pekinensis • H. e. soloensis) • H. cepranensis • H. antecessor • H. heidelbergensis • H. neanderthalensis • H. rhodesiensis • H. floresiensis • Homo sapiens (H. s. idaltu • H. s. sapiens)
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