Human taxonomy

Human taxonomy is the classification of the species "Homo sapiens" (Latin: "wise man"), or modern human. "Homo" is the human genus, which also includes Neanderthals and many other extinct species of hominid; "H. sapiens" is the only surviving species of the genus "Homo". Extinct "Homo" species are known as archaic humans. Modern humans are the subspecies "Homo sapiens sapiens", differentiated from a direct ancestor, "Homo sapiens idaltu".

Prior to the current scientific classification of humans, philosophers and scientists have made various attempts to classify humans. They offered various definitions of the human being and various schemes for classifying types of humans. Biologists once classified races as subspecies, but today scientists question even the concept of race itself. Certain issues in human taxonomy remain topics of debate today.

Extended scientific classification

The modern scientific classification of the human species contains many sub- and super- sections (each one being, ideally, a clade) which have been interpolated between the seven traditional Linnaean taxonomic ranks.

Humans are not only the sole surviving representatives of the genus "Homo" but also the only surviving representatives of the subtribe "Hominina", which includes "Australopithecus" and other more anthropomorphic hominids. Species believed to be ancestors are listed within higher taxa.

* Biota [all life on Earth]
*Cytota [all cellular life]
*Neomura [contains Eukarya and Archaea]
*Eukarya (Domain)
*Unikonta [only one flagellum]
*Opisthokonts [animals and fungi]
*Animalia (Kingdom)
*Eumetazoa (Subregnum)
*Bilateria [having bilateral symmetry]
*Coelomata [...and a fluid-filled body cavity]
*Deuterostomia (Superphylum)
*Chordata (Phylum)
*Craniata [animals with skulls]
*Vertebrata (Subphylum) [...and backbones]
*Gnathostomata (Infraphylum) [...and jaws]
*Teleostomi [advanced fish and descendants]
*Euteleostomi [bony vertebrates]
*Sarcopterygii
*Tetrapoda (Superclass) [...and four limbs]
*Amniota (Series) [...and amniotic eggs]
*Synapsida [mammal-like reptiles]
*Mammaliaformes / Mammalia (Class) [all mammals]
*Theria (Subclass)
*Eutheria
*Euarchontoglires (Superorder)
*Euarchonta (Superorder)
*Primates (Order)
*Haplorrhini (Suborder)
*Simiiformes (Infraorder) [apes and monkeys]
*Catarrhini (Parvorder)
*Hominoidea (Superfamily) [apes] :"Proconsul africanus"
*Hominidae (Family) [great apes]
*Homininae (Subfamily) [includes gorillas but not orangutans] :"Pierolapithecus catalaunicus"
*Hominini (Tribe) [includes chimpanzees but not gorillas] :"Sahelanthropus tchadensis", common ancestor with chimpanzeesFact|date=January 2008:"Orrorin tugenensis", first species after split with chimpanzeesFact|date=January 2008
*Hominina (Subtribe) [humans are the only surviving species] :"Ardipithecus":"Kenyanthropus":Australopithecines: includes "Paranthropus" and "Australopithecus"::"Australopithecus"::"Paranthropus"
*Homo (Genus):"Homo habilis":"Homo ergaster":"Homo erectus":"Homo heidelbergensis"
*"Homo sapiens" (Species) :"Homo sapiens idaltu"
*"Homo sapiens sapiens" (Subspecies)

Current issues in human taxonomy

Generally, humans are considered the only surviving representatives of the genus "Homo". Some scientists, however, consider other members of the hominid family (chimpanzees and gorillas) to be so close to humans genetically that they should be classified as "Homo".

Scientists have also debated whether any other branches of "Homo", such as Neanderthals, should be classified as separate species or subspecies of "H. sapiens". These distinctions are connected with two competing theories of human origins, the more common recent single-origin hypothesis (that modern humans represent a distinct gene pool) and the multiregional hypothesis (that modern humans spreading from Africa interbred with local "Homo" populations). Modern humans have some genes that originally arose in archaic human populations, composing perhaps 5% of our genetic inheritance. (For example, see microcephalin.)

Species within the genus "Homo" are generally regarded as human. Australopithecines, too, are often referred to as human. Lay people sometimes ask whether the species other than "H. sapiens" were truly human. Were Neanderthals, for example, actually human or just close to human? This question makes sense in an essentalist philosophy, in which humans have an essential identity, and in which Neanderthals either did or did not share that identity. In metaphysical context, the question might be phrased as "Did Neanderthals have souls?" In natural science, however, the term "human" is seen as a category whose boundaries humans themselves determine. The question, in this context, is not whether this or that species had the quality of being human in some absolute sense, but whether we choose to define the category of human as including that species.

History of human taxonomy

Human taxonomy has involved both placing humans within the hominid family (or within the animal kingdom in general) and classifying types of humans within the species.

History of classifying the human species

As recorded in the Hebrew Bible, ancient Hebrews classified humans as a kind of living soul ("nephesh", roughly "breather"). Living things were said to beget their own kind, a group broader than the scientific species. Humans were said to comprise a single kind.

Humans have long been considered animals. Plato referred to humans as featherless biped animals, and Aristotle defined the human being as the "rational animal" or the "political animal". Classic and medieval taxonomy grouped living things according to characteristics, and classifying humans as animals meant that they have various animal characteristics (moving, eating, breathing, etc.). Modern taxonomy, on the other hand, classifies organisms according to evolutionary lines of descent. Current opposition to classifying humans as animals arises from this modern definition of what it means to be an animal (that is, a descendent of a common animal ancestor that lived over 500 million years ago).

When Linnaeus defined humans as "Homo sapiens" in 1758, they were the only members of the genus "Homo". The first other species to be classified a "Homo" was "H. neanderthalensis", classified in 1864. Since then, ten additional extinct species have been classified as "Homo".

In a common misunderstanding of evolutionary theory, each species represents a stage in the evolutionary track, some “more evolved” and others further behind. Based on this misunderstanding, scientists thought of humans as having descended from modern apes and expected to find the “missing link,” a living species halfway between apes and humans.

History of classifying types of humans

Europeans in the Middle Ages considered humanity to be divided into three races, one for each of the sons of Noah (see Japhetic). This concept was so powerful when Europeans discovered Americans some of them considered the Americans to be soulless animals.

Races were once considered human subspecies, but genetic research shows that inherited differences do not accurately match common racial divisions. For example, since non-Africans are descended from a small population that emigrated from Africa about 100,000 years ago, non-Africans (even those representing difference races) are more closely related to each other than Africans are to each other.

ee also

*Timeline of human evolution