HOMINIDAE

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The 'hominids' are the members of the biological family 'Hominidae' (the 'great apes'), which includes humans, chimpanzees, gorillas, and orangutans.^[1]
This classification has been revised several times in the last few decades. Originally, the group was restricted to humans and their extinct relatives, with the other great apes being placed in a separate family, the 'Pongidae'. This definition is still used by many anthropologists and by lay people. However, that definition makes Pongidae paraphyletic, whereas most taxonomists nowadays encourage monophyletic groups. Thus many biologists consider Hominidae to include Pongidae as the subfamily Ponginae, or restrict the latter to the orangutans and their extinct relatives like ''Gigantopithecus''. The taxonomy shown here follows the monophyletic groupings.
Especially close human relatives form a subfamily, the Homininae. Some researchers go so far as to include chimpanzees^[2] and gorillas in the genus ''Homo'' along with humans, but it is more commonly accepted to describe the relationships as shown here.
Many extinct hominids have been studied to help understand the relationship between modern humans and the other extant hominids. Some of the extinct members of this family include ''Gigantopithecus'', ''Orrorin'', ''Ardipithecus'', ''Kenyanthropus'', and the australopithecines ''Australopithecus'' and ''Paranthropus''.
The exact criteria for membership in the Homininae are not clear, but the subfamily generally includes those species which share more than 97% of their DNA with the modern human genome, and exhibit a capacity for language or for simple cultures beyond the family or band. The theory of mind including such faculties as mental state attribution, empathy and even empathetic deception is a controversial criterion distinguishing the adult human alone among the hominids. Humans acquire this capacity at about four and a half years of age, whereas it has neither been proven nor disproven that gorillas and chimpanzees develop a theory of mind.^[3] This is also the case for some new world monkeys outside the family of great apes, as, for example, the capuchin monkeys.
However, without the ability to test whether early members of the Homininae (such as ''Homo erectus'', ''Homo neanderthalensis'', or even the australopithecines) had a theory of mind, it is difficult to ignore similarities seen in their living cousins. Despite an apparent lack of real culture and significant physiological and psychological differences, some say that the orangutan may also satisfy these criteria. These scientific debates take on political significance for advocates of Great Ape personhood.
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. A report on this finding was published in the journal ''Nature'' on July 11, 2002. 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''.
In addition to the Toumai fossil, some experts use evidence from the genome to argue that the species associated with the chimpanzees and proto-humans split interbred over a long period of time, swapping genes, before making a final separation. A paper, whose authors include David Reich and Eric Lander (Harvard and the Massachusetts Institute of Technology (MIT)), was published in journal ''Nature'' in May 2006.
It is generally believed that the ''Pan/Homo'' split occurred about 6.5–7.4 million years ago, but the molecular clock (a method of calculating evolution based on the speed at which genes mutate) suggests the genera split 5.4–6.3 million years ago. Previous studies looked at average genetic differences between human and chimp. The new study compares the ages of key sequences of genes of modern humans and modern chimps. Some sequences are younger than others, indicating that chimps and humans gradually split apart over a period of 4 million years. The youngest human chromosome is the X sex chromosome which is about 1.2 million years more recent than the 22 autosomes. The X chromosome is known to be vulnerable to selective pressure. Its age suggests there was an initial split between the two species, followed by gradual divergence and interbreeding that resulted in younger genes, and then a final separation.

Contents

Classification

See also

References

External links

Classification

★ 'Family Hominidae': humans and other great apes; extinct genera and species excluded.

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★ Subfamily Ponginae

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★ Genus ''Pongo''

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★ Bornean Orangutan, ''Pongo pygmaeus''

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★ ''Pongo pygmaeus pygmaeus''

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★ ''Pongo pygmaeus morio''

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★ ''Pongo pygmaeus wurmbii''

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★ Sumatran Orangutan, ''Pongo abelii''

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★ Subfamily Homininae

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★ Tribe Gorillini

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★ Genus ''Gorilla''

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★ Western Gorilla, ''Gorilla gorilla''

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★ Western Lowland Gorilla, ''Gorilla gorilla gorilla''

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★ Cross River Gorilla, ''Gorilla gorilla diehli''

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★ Eastern Gorilla, ''Gorilla beringei''

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★ Mountain Gorilla, ''Gorilla beringei beringei''

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★ Eastern Lowland Gorilla, ''Gorilla beringei graueri''

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★ Tribe Hominini

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★ Genus ''Pan''

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★ Common Chimpanzee, ''Pan troglodytes''

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★ Central Chimpanzee, ''Pan troglodytes troglodytes''

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★ West African Chimpanzee, ''Pan troglodytes verus''

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★ Nigerian Chimpanzee, ''Pan troglodytes vellerosus''

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★ Eastern Chimpanzee, ''Pan troglodytes schweinfurthii''

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★ Bonobo (Pygmy Chimpanzee), ''Pan paniscus''

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★ Genus ''Homo''

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★ Human, ''Homo sapiens sapiens''
In addition to the extant species and subspecies above, archaeologists, paleontologists, and anthropologists have discovered numerous extinct species. The list below are some of the genera of those discoveries.

★ Subfamily Ponginae

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★ ''Gigantopithecus''†

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★ ''Sivapithecus''†

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★ ''Lufengpithecus''†

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★ ''Ankarapithecus''†

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★ ''Ouranopithecus''†

★ Subfamily Homininae

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★ ''Homo'' - Humans and their immediate ancestors

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★ ''Oreopithecus''†

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★ ''Paranthropus''†

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★ ''Australopithecus''†

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★ ''Sahelanthropus''†

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★ ''Orrorin''†

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★ ''Ardipithecus''†

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★ ''Kenyanthropus''†

See also

★ Kinshasa Declaration on Great Apes

★ Ape extinction

★ Declaration on Great Apes

★ Evolution of Homo sapiens

★ Evolutionary neuroscience

★ Graphical timeline of human evolution

★ Great ape language

★ Great Ape Project

★ List of apes - notable individual apes

★ ''The Mind of an Ape''

★ Great Ape research ban

★ Great Apes Survival Project

References

1. "Great ape" is a common name rather than a taxonomic label and there are differences in usage. Subtly, it may seem to exclude human beings ("humans and the great apes") or to include them ("humans and non-human great apes"). ''Homo sapiens'' is not at any especial remove from other members of the biological family, and humans are therefore described here as great apes.
2. Chimps Belong on Human Branch of Family Tree, Study Says Pickrell, John
3. Theory of Mind in Nonhuman Primates, Heyes, C. M., , , Behavioral and Brain Sciences, 1998

External links

★ Additional information on great apes

★ NPR News: Toumaï the Human Ancestor

★ Hominid Species at talkorigins.org

★ For more details on Hominid species, including excellent photos of fossil hominids

★ New Scientist 19 May 2003 - Chimps are human, gene study implies

★ Scientific American Magazine (April 2006 Issue) Why Are Some Animals So Smart?