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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.
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, bonobos, 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 essentialist philosophy, in which humans have an essential identity, and in which Neanderthals either did or did not share that identity. In religious 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. Remnants of beliefs related to the Great Chain of Being were not only the origin of the term "missing link", but through the concept that a perfect creator would create things perfectly, extinction would be impossible and any species that ever lived would still be alive in some part of the world, awaiting discovery.
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 the New World some of them considered the indigenous peoples 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 different races) are more closely related to each other than Africans are to each other.