Hominini

From Infogalactic: the planetary knowledge core
Jump to: navigation, search
Hominins
Temporal range: 5.4–0 Ma
230px
Skull of Sahelanthropus tchadensis, described as the earliest member of the hominin line,[1] but this is debated[2]
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Family: Hominidae
Subfamily: Homininae
Tribe: Hominini
Gray, 1825
Type species
Homo sapiens
Linnaeus, 1758
Genera

Panina
†Australopithecine
Hominina

Lua error in Module:Taxonbar/candidate at line 22: attempt to index field 'wikibase' (a nil value). <templatestyles src="Module:Hatnote/styles.css"></templatestyles>

Not to be confused with Ape, Hominidae, Homininae, or Homo.

The Hominini is a taxonomical tribe of the subfamily Homininae; it comprises three subtribes: Hominina, with its one genus Homo; Australopithecina, comprising several extinct genera (see inset to right); and Panina, with its one genus Pan, the chimpanzees (see the evolutionary tree below).[3][4] Members of the human clade, that is, the Hominini, including Homo and those species of the australopithecines that arose after the split from the chimpanzees, are called hominins; cf. Hominidae; terms "hominids" and hominins). Not all hominins are directly related to the emergence of early Homo.[5]

The subtribe Hominina is the "human" branch; that is, it contains the genus Homo exclusively. Researchers proposed the taxon Hominini on the basis that the least similar species of a trichotomy should be separated from the other two. The common chimpanzee and the bonobo of the genus Pan are the closest living evolutionary relatives to humans, sharing a common ancestor with humans about four to seven million years ago.[6] Research by Mary-Claire King in 1973 found 99% identical DNA between humans and chimpanzees;[7] later research modified that finding to about 94% commonality, with some of the difference occurring in noncoding DNA.[8]

Taxonomy

All the extinct genera listed to the right are ancestral to, or offshoots of, Homo. Few fossil specimens on the Pan side of the split have been found—the first discovery of a fossil chimpanzee was published in 2005;[9] it was from Kenya's East African Rift Valley and dated to between 545 thousand years, radiometric, (kyr) and 284 kyr (via argon–argon dating). However, both Orrorin and Sahelanthropus existed around the time of the split, and so may be ancestral to both Pan and Homo.

Evolutionary tree chart emphasizing the subfamily Homininae and the tribe Hominini. After diverging from the line to Ponginae the early Homininae split into the tribes Hominini and Gorillini. The early Hominini split further, separating the line to Homo from the lineage of Pan. Currently, tribe Hominini designates the subtribes Hominina, containing genus Homo; Panina, with genus Pan; and Australopithecina, with several extinct genera—see taxobox; the subtribes are not labelled on this chart.

In the proposal of Mann and Weiss (1996),[10] the tribe Hominini includes Pan as well as Homo, but within separate subtribes. Homo and (by inference) all bipedal apes are referred to the subtribe Hominina, while Pan is assigned to the subtribe Panina. Wood (2010) discusses the different views of this taxonomy.[11]

A source of confusion in determining the exact age of the Pan–Homo split is evidence of a complex speciation process rather than a clean split between the two lineages. Different chromosomes appear to have split at different times, possibly over as much as a four-million-year period, indicating a long and drawn out speciation process with large-scale hybridization events between the two emerging lineages as late as 6.3 to 5.4 million years ago according to Patterson et al. (2006).[12]

The assumption of late hybridization was in particular based on the similarity of the X chromosome in humans and chimpanzees, suggesting a divergence as late as some 4 million years ago. This conclusion was rejected as unwarranted by Wakeley (2008), who suggested alternative explanations, including selection pressure on the X chromosome in the populations ancestral to the chimpanzee–human last common ancestor (CHLCA).[13]

Sahelanthropus tchadensis is an extinct hominid species that lived seven million years ago, very close to the time of the chimpanzee–human divergence.[citation needed] It is unclear whether or not it may be classed as hominin—that is, whether it rose after the split from the chimpanzees, or not.

Pan-Homo divergence

Lua error in package.lua at line 80: module 'strict' not found.

See also

References

  1. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Mary-Claire King (1973) Protein polymorphisms in chimpanzee and human evolution, Doctoral dissertation, University of California, Berkeley.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found. "Patterson et al. suggest that the apparently short divergence time between humans and chimpanzees on the X chromosome is explained by a massive interspecific hybridization event in the ancestry of these two species. However, Patterson et al. do not statistically test their own null model of simple speciation before concluding that speciation was complex, and—even if the null model could be rejected—they do not consider other explanations of a short divergence time on the X chromosome. These include natural selection on the X chromosome in the common ancestor of humans and chimpanzees, changes in the ratio of male-to-female mutation rates over time, and less extreme versions of divergence with gene flow. I therefore believe that their claim of hybridization is unwarranted."
Retrieved from "https://infogalactic.com/w/index.php?title=Hominini&oldid=784096"