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Human Evolution

Humans cannot be studied appart from other mammalian species, no matter how distinct our anatomy is or if our culture is more sophhisticated than that of other animals. Paleoanthropology is the scientific discipline that studies the origin, evolution and dispersal, both in time and space, of the hominin lineage. We belong to the Homo sapiens species. The Linnean dicotomic taxonomic system, defined by Carolus Linnaeus (1707-1778) (Systema Naturae, 1735), establishes that all species are refferred to with a double (dicotomic) name including the genus name (Homo) and the species attribute that should always include the genus name (Homo sapiens). In case sevaral distinct populations can be distinguished within one species, a subspecies attribute may be added (Homo sapiens sapiens). Species names and attributes should always be written in italics or underlined (Homo sapiens) and the genus can be shortened (H. sapiens), as well as the species attribute when the subspecies one is used (H. s. sapiens). Linnaeus defined two human species: Homo sylvestris and Homo sapiens, and within the latter he described six subspecies (H. s. ferus, H. s. monstruosus, H. s. afer, H. s. europaeus, H. s. asiaticus and H. s. americanus). Despite this classification was wrong, Linnaeus created a precise way to classify organisms into a hierarquical way in which closely related species had to be grouped into the same taxonomic clade.

Taxonomy is the set of rules that asignes a species name to an organisms and classifes it into taxonomic groups according to the similarities of its anatomical and genetic traits with other species. In fact, the taxonomy of a group of organismis should reflect their phylogeny, their relationships of ancesto-descendant. Taxonomic groups should be monophyletic, which means that they have to share a unic common ancestor. If this requirement is not met, the group is said to be polyphyletic. Humans have traditionally been clasified into a distinc family (F. Hominidae), separated from the chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla) and orangutans (Pongo pygmaeus), that were initially classified into a separate family (F. Pongidae). However, chimpanzees and humas share a unique common ancestor closer in time than those that humans share with the other hominoidea (Sp.F. Hominoidea), formerly called pongids. Therefore, classifying humans alone into a distinct taxonomic clade does not reflect the actual phylogeny of the group. Humans, chimpanzees, gorillas and orangutans should be all classified into the same family. Thus, the term hominids no longer refers exclusively to the human ancestors, but to the ancestors of all the great apes, excluding the gibons, referred to as lesser apes. Since we belong to the hominini tribe, our ancestors should be referred to as the homininins, or simply the hominines, instead of the hominids, which is a broader, more inclusive category.

This Human Evolution subject will provide a reliable overview of how hominins evolved within the mammals and primates.

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