Homininae

Homininae
Temporal range: 23.03–0 Ma
Western gorilla
(Gorilla gorilla)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Infraorder: Simiiformes
Superfamily: Hominoidea
Family: Hominidae
Subfamily: Homininae
Gray, 1825
Genera

Gorillini
Hominini
and see text

For an explanation of very similar terms, see Hominidae.

Homininae is a subfamily of Hominidae that includes the tribes Hominini and Gorillini, which together encompass humans and some extinct relatives, chimpanzees and bonobos, as well as gorillas. It comprises all hominids that arose after orangutans (subfamily Ponginae) split from the line of great apes. The Homininae cladogram has three main branches, which lead to gorillas (through the tribe Gorillini), and to humans and chimpanzees via the tribe Hominini and subtribes Hominina and Panina, (see the evolutionary tree below). There are two living species of chimpanzees and two living species of gorillas, but only one extant human species. Traces of hypothetical Homo species, including Homo floresiensis and Homo denisova, have been found with dates as recent as 12,000 years ago. Organisms in this class are described as hominine or hominines (not to be confused with the terms hominins or hominini).

History of discoveries and classification

Until 1980, the family (and term) Hominidae meant humans only; the non-human great apes were assigned to the family Pongidae.[1] Later discoveries led to revised classifications, with the great apes then united with humans (now in subfamily Homininae) as members of family Hominidae [2] Further discoveries indicated that gorillas and chimpanzees are more closely related to humans than they are to orangutans, leading to their (gorillas and chimpanzees) placement in subfamily Homininae as well.[3]

The subfamily Homininae can be further subdivided into three branches: the tribe Gorillini (gorillas), and the tribe Hominini with subtribes Panina (chimpanzees) and Hominina (humans and their extinct relatives). The Late Miocene fossil Nakalipithecus nakayamai, described in 2007, is a basal member of this clade, as is, perhaps, its contemporary Ouranopithecus; that is, they are not assignable to any of the three extant branches. Their existence suggests that the Homininae tribes diverged not earlier than about 8 million years ago (see Human evolutionary genetics).

Today, chimpanzees and gorillas live in tropical forests with acid soils that rarely preserve fossils. Although no fossil gorillas have been reported, four chimpanzee teeth about 500,000 years old have been discovered in the East-African rift valley (Kapthurin Formation, Kenya), where many fossils from the human lineage (hominins)[Note 1] have been found.[4] This shows that some chimpanzees lived close to Homo (H. erectus or H. rhodesiensis) at the time; the same is likely true for gorillas.

Taxonomic classification

Homininae[5][6]

Evolution

Evolution of bipedalism

Recent studies of Ardipithecus ramidus (4.4 million years old) and Orrorin tugenensis (6 million years old) suggest some degree of bipedalism. Australopithecus and early Paranthropus may have been bipedal. Very early hominins such as Ardipithecus ramidus may have possessed an arboreal type of bipedalism.[10] and towards efficient walking and running in modern humans.

Brain size evolution

There has been a gradual increase in brain volume (brain size) as the ancestors of modern humans progressed along the timeline of human evolution, starting from about 600 cm3 in Homo habilis up to 1500 cm3 in Homo sapiens neanderthalensis. However, modern Homo sapiens have a brain volume slightly smaller (1250 cm3) than Neanderthals, women have a brain slightly smaller than men and the Flores hominids (Homo floresiensis), nicknamed hobbits, had a cranial capacity of about 380 cm3 (considered small for a chimpanzee), about a third of the Homo erectus average. It is proposed that they evolved from H. erectus as a case of insular dwarfism. In spite of their smaller brain, there is evidence that H. floresiensis used fire and made stone tools at least as sophisticated as those of their proposed ancestors H. erectus.[11] In this case, it seems that for intelligence, the structure of the brain is more important than its size.[12]

Evolution of family structure and sexuality

See also: Human sexuality

Sexuality is related to family structure and partly shapes it. The involvement of fathers in education is quite unique to humans, at least when compared to other Homininae. Concealed ovulation and menopause in women both also occur in a few other primates however, but are uncommon in other species. Testis and penis size seems to be related to family structure: monogamy or promiscuity, or harem, in humans, chimpanzees or gorillas, respectively.[13][14] The levels of sexual dimorphism are generally seen as a marker of sexual selection. Studies have suggested that the earliest hominins were dimorphic and that this lessened over the course of the evolution of the genus Homo, correlating with humans becoming more monogamous, whereas gorillas, who live in harems, show a large degree of sexual dimorphism. Concealed (or "hidden") ovulation means that the phase of fertility is not detectable in women, whereas chimpanzees advertise ovulation via an obvious swelling of the genitals. Women can be partly aware of their ovulation along the menstrual phases, but men are essentially unable to detect ovulation in women. Most primates have semi-concealed ovulation, thus one can think that the common ancestor had semi-concealed ovulation, that was inherited by gorillas, and that later evolved in concealed ovulation in humans and advertised ovulation in chimpanzees. Menopause also occurs in rhesus monkeys, and possibly in chimpanzees, but does not in gorillas and is quite uncommon in other primates (and other mammal groups).[14]

See also

Notes

  1. ↑ A hominin is a member of the tribe Hominini, a hominine is a member of the subfamily Homininae, a hominid is a member of the family Hominidae, and a hominoid is a member of the superfamily Hominoidea.

Citations

Wikispecies has information related to: Homininae
The Wikibook Dichotomous Key has a page on the topic of: Homininae
  1. ↑ Goodman, M. (1964). "Man’s place in the phylogeny of the primates as reflected in serum proteins". In Washburn, S.L. Classification and Human Evolution. Transaction Publishers. pp. 204–234. ISBN 978-0-202-36487-2.
  2. ↑ Goodman, M. (1974). "Biochemical Evidence on Hominid Phylogeny". Annual Review of Anthropology 3: 203–228. doi:10.1146/annurev.an.03.100174.001223.
  3. ↑ Goodman M., Tagle D.A., Fitch D.H., Bailey W., Czelusniak J., Koop B.F., Benson P., Slightom J.L. (1990). "Primate evolution at the DNA level and a classification of hominoids". Journal of Molecular Evolution 30 (3): 260–6. doi:10.1007/BF02099995. PMID 2109087.
  4. ↑ McBrearty S, Jablonski N (2005). "First fossil chimpanzee". Nature 437 (7055): 105–8. doi:10.1038/nature04008. PMID 16136135.
  5. ↑ Haaramo, Mikko (2005-01-14). "Hominoidea". Mikko's Phylogeny Archive.
  6. ↑ Haaramo, Mikko (2007-11-10). "Hominidae". Mikko's Phylogeny Archive.
  7. ↑ "Praeanthropus garhi Asfaw 1999 (ape)". Paleobiology Database. Fossilworks.
  8. ↑ Barras, Colin (2012-03-14). "Chinese human fossils unlike any known species". New Scientist. Retrieved 2012-03-15.
  9. ↑ "Orangutan Pongo pygmaeus". Animals. National Geographic Society. Retrieved 25 July 2009.
  10. ↑ Kivell TL, Schmitt D (August 2009). "Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor". Proc. Natl. Acad. Sci. U.S.A. 106 (34): 14241–6. doi:10.1073/pnas.0901280106. PMC 2732797. PMID 19667206.
  11. ↑ Brown P, Sutikna T, Morwood MJ, et al. (2004). "A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia". Nature 431 (7012): 1055–61. doi:10.1038/nature02999. PMID 15514638.
  12. ↑ Davidson, I. (2007). "As large as you need and as small as you can—implications of the brain size of Homo floresiensis". In Schalley, A.C.; Khlentzos, D. Mental States: Evolution, function, nature; 2. Language and cognitive structure. Studies in language companion. 92–93. John Benjamins. pp. 35–42. ISBN 9027231052.
  13. ↑ Diamond, Jared (1991). The Third Chimpanzee.
  14. 1 2 Diamond, Jared (1997). Why is Sex Fun?.

References

  • Hollox, Edward; Hurles, Matthew; Kivisild, Toomas; Tyler-Smith, Chris (2013). Human Evolutionary Genetics (2nd ed.). Garland Science. ISBN 978-0-8153-4148-2. 
  • "Homininae". NCBI Taxonomy Browser. 207598. 
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