Temporal range: 0.2–0 Ma Middle Pleistocene–Present
|Male and female H s. sapiens
(Akha in northern Thailand,
Homo sapiens is the systematic name used in taxnomy (also known as binomial nomenclature) for anatomically modern humans, i.e. the only extant human species. The name is Latin for "wise man" and was introduced in 1758 by Carl Linnaeus (who is himself also the type specimen).
Extinct species of the genus Homo are classified as "archaic humans". This includes at least the separate species Homo erectus, and possibly a number of other species (which are variously also considered subspecies of either H. sapiens or H. erectus. H. sapiens idaltu (2003) is a proposed extinct subspecies of H. sapiens.
The age of speciation of H. sapiens out of ancestral H. erectus (or an intermediate species such as Homo heidelbergensis) is estimated to have taken place at roughly 315,000 years ago. However, there is known to have been continued admixture from archaic human species until as late as some 30,000 years ago; this is also the time of disappearance of any surviving archaic human species, which were apparently absorbed by the recent Out-Of-Africa expansion of Homo sapiens beginning some 50,000 years ago.
Name and taxonomy
Extant human populations have historically been divided into subspecies, but since c. the 1980s all extant groups tend to be subsumed into a single species, H. sapiens, avoiding division into subspecies altogehter.
Some sources show Neanderthals (Homo neanderthalensis) as a subspecies (Homo sapiens neanderthalensis). Similarly, the discovered specimens of the Homo rhodesiensis species have been classified by some as a subspecies (Homo sapiens rhodesiensis), although it remains more common to treat these last two as separate species within the Homo genus rather than as subspecies within H. sapiens.
Age and speciation process
Traditionally, there are two competing views in paleoanthropology about the origin of H. sapiens: the recent African origin and the multiregional origin. Since 2010, genetic research has led to the emergence of an intermediate position, characterised by mostly recent African origin with the addition of limited admixture (introgression) from archaic humans.
The recent African origin of modern humans is the mainstream model that describes the origin and early dispersal of anatomically modern humans. The theory is called the (Recent) Out-of-Africa model in the popular press, and academically the recent single-origin hypothesis (RSOH), Replacement Hypothesis, and Recent African Origin (RAO) model. The hypothesis that humans have a single origin (monogenesis) was published in Charles Darwin's Descent of Man (1871). The concept was speculative until the 1980s, when it was corroborated by a study of present-day mitochondrial DNA, combined with evidence based on physical anthropology of archaic specimens. According to genetic and fossil evidence, archaic Homo sapiens evolved to anatomically modern humans solely in Africa, roughly 200,000 years ago, with members of one branch leaving Africa by 60,000 years ago and over time replacing earlier human populations, such as Neanderthals and Homo erectus. More recently, in 2017, fossils found in Jebel Irhoud (Morocco) suggest that Homo sapiens may have evolved as early as 315,000 years ago; and other evidence suggests that Homo sapiens may have migrated from Africa as early as 120,000 years ago, particularly into Asia, and even as early as 270,000 years ago.
However, significant archaic human admixture with modern humans in was discovered in the 2010s. Green et al. (2010) suggest that their findings are consistent with Neanderthal admixture of up to 4% in some populations. But the study also suggests that there may be other reasons why humans and Neanderthals share ancient genetic lineages. In August 2012, a study by scientists at the University of Cambridge questioned this conclusion, hypothesising instead that the DNA overlap is a remnant of a common ancestor of both Neanderthals and modern humans. That study however does not explain why only a fraction of modern humans have Neanderthal DNA.
The multiregional origin model, proposed by Milford H. Wolpoff in 1988 provides another explanation for the pattern of human evolution. Multiregional origin holds that the evolution of humanity from the beginning of the Pleistocene 2.5 million years BP to the present day has been within a single, continuous human species.
Homo sapiens idaltu, the other known subspecies, is now extinct. Homo neanderthalensis, which became extinct 30,000 years ago, has sometimes been classified as a subspecies, "Homo sapiens neanderthalensis"; genetic studies now suggest that the functional DNA of modern humans and Neanderthals diverged 500,000 years ago.
The Omo remains (discovered between 1967 and 1974), dated to some 195,000 years ago, were long considered the oldest known fossils identifiable as anatomically modern humans. A number of studies molecular biology conducted between 2005 and 2010 have yielded results compatible with the age of the Omo remains, placing the common ancestor of all modern human populations[dubious ] some 200,000 years ago.
The San people of Southern Africa have been found to be the human population with the deepest temporal division from all other contemporary populations, estimated at close to 130,000 years ago. A 2011 study has classified them as one of "ancestral population clusters". The same study also located the origin of the first wave of expansion of H. sapiens, beginning roughly 130,000 years ago, in southwestern Africa, near the coastal border of Namibia and Angola.
Following the second Out-of-Africa expansion, some 70,000 to 50,000 years ago, some subpopulations of H. sapiens have been essentially isolated for tens of thousands of years prior to the early modern Age of Discovery. Combined with archaic admixture this has resulted in significant genetic variation, which in some instances has been shown to be the result of directional selection taking place over the past 15,000 years, i.e. significantly later than possible archaic admixture events.
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