Multiregional origin of modern humans The multiregional hypothesis, multiregional evolution (MRE), or polycentric hypothesis is a scientific model that provides an alternative explanation to the more widely accepted "Out of Africa" model of monogenesis for the pattern of human evolution. Multiregional evolution holds that the human species first arose around two million years ago and subsequent human evolution has been within a single, continuous human species. This species encompasses all archaic human forms such as H. erectus and Neanderthals as well as modern forms, and evolved worldwide to the diverse populations of anatomically modern humans (Homo sapiens). The hypothesis contends that the mechanism of clinal variation through a model of "Centre and Edge" allowed for the necessary balance between genetic drift, gene flow and selection throughout the Pleistocene, as well as overall evolution as a global species, but while retaining regional differences in certain morphological A graph detailing the evolution to modern humans features.[1] Proponents of multiregionalism point to fossil and using the multiregional hypothesis ofhuman genomic data and continuity of archaeological cultures as support for evolution. The horizontal lines represent their hypothesis. 'multiregional evolution' gene flow between regional lineages. In Weidenreich's original graphic The multiregional hypothesis was first proposed in 1984, and then (which is more accurate than this one), there were also diagonal lines between the populations, e.g. revised in 2003. In its revised form, it is similar to the Assimilation between African H. erectus and Archaic Asians Model.[2] and between Asian H. erectus and Archaic Africans. This created a "trellis" (as Wolpoff called it) or a "network" that emphasized gene flow between geographic regions and within time. It is Contents important to remember that the populations on the History chart are not discrete – i.e., they do not represent Overview different species, but are samples within a long "Classic" vs "weak" multiregionalism lineage experiencing extensive gene flow. Genetic studies Fossil evidence Morphological clades Indonesia, Australia China Europe Genetic evidence Mitochondrial Eve Neanderthal mtDNA Nuclear DNA Ancient DNA Recent African origin See also References Further reading External links History Overview Hominin timeline 0 — The Multiregional hypothesis was proposed in 1984 by ←Modern humans P Neanderthals Homo sapiens ←Modern speech Milford H. Wolpoff, Alan Thorne and Xinzhi Wu.[3][4][1] – l H. heidelbergensis ←Earliest clothes e Wolpoff credits Franz Weidenreich's "Polycentric" ←Earliest cooking -1 — i hypothesis of human origins as a major influence, but s Homo erectus – t ←Earliest fire use cautions that this should not be confused with polygenism, o ←Exit from Africa or Carleton Coon's model that minimized gene -2 — c e flow.[4][5][6] According to Wolpoff, multiregionalism was Homo habilis – n misinterpreted by William W. Howells, who confused e Weidenreich's hypothesis with a polygenic "candelabra -3 — ←Stone tools model" in his publications spanning five decades: – Australopithecus P -4 — l ←Earliest bipedal How did Multiregional evolution get i Ardipithecus stigmatized as polygeny? We believe it – o H c comes from the confusion of Weidenreich's -5 — e o ideas, and ultimately of our own, with n – e Hominini m Coon's. The historic reason for linking ←Chimpanzee split Coon's and Weidenreich's ideas came from -6 — Orrorin i the mischaracterizations of Weidenreich's – n Polycentric model as a candelabra i (Howells, 1942, 1944, 1959, 1993), that -7 — M Sahelanthropus ←Possibly bipedal i made his Polycentric model appear much d – o more similar to Coon's than it actually c s -8 — e was.[7] n – e Through the influence of Howells, many other -9 — Ouranopithecus ←Gorilla split anthropologists and biologists have confused – multiregionalism with polygenism i.e. separate or multiple Nakalipithecus -10 — ←Earlier apes origins for different populations. Alan Templeton for Axis scale: million years example notes that this confusion has led to the error that Also see: Life timeline and Nature timeline gene flow between different populations was added to the Multiregional hypothesis as a "special pleading in response to recent difficulties", despite the fact: "parallel evolution Ice Ages Life timeline was never part of the multiregional model, much less its 0 — Quaternary Primates ←Earliest apes core, whereas gene flow was not a recent addition, but P Flowers Birds Mammals h rather was present in the model from the very – Dinosaurs Paleozoic a Plants n ← beginning"[8] (emphasis in original). Despite this, Andean Tetrapoda -500 — e Arthropods and Molluscs multiregionalism is still confused with polygenism, or r ←Cambrian explosion Cryogenian o ←Ediacaran biota Coon's model of racial origins, from which Wolpoff and – z o ←Earliest plants his colleagues have distanced themselves.[9][10] Wolpoff i -1000 — c Multicellular life has also defended Wiedenreich's Polycentric hypothesis ←Sexual from being labeled polyphyletic. Weidenreich himself in – reproduction P r -1500 — o -1500 — o 1949 wrote: "I may run the risk of being misunderstood, t – e namely that I believe in polyphyletic evolution of r Eukaryotes o man".[11] z -2000 — o In 1998, Wu founded a China-specific Multiregional Huronian – i c ←Oxygen crisis model called "Continuity with [Incidental] -2500 — ←Atmospheric oxygen Hybridization".[12][13] Wu's variant only applies the Multiregional hypothesis to the East Asian fossil record – photosynthesis Pongola which is popular among Chinese scientists.[14] However, -3000 — A James Leibold a political historian of modern China has r c argued the support for Wu's model is largely rooted in – h [15] e Chinese nationalism. Outside of China, the a -3500 — ← Multiregional hypothesis has limited support, held only by n Earliest oxygen [16] a small number of paleoanthropologists. – Single-celled life -4000 — ←Earliest life H "Classic" vs "weak" multiregionalism a water – d Chris Stringer, a leading proponent of the more e a ←Earliest water mainstream recent African origin theory, debated -4500 — n ←Earth (−4540) Axis scale: million years Multiregionalists such as Wolpoff and Thorne in a series of Also see: Human timeline and Nature timeline publications throughout the late 1980s and 1990s.[17][18][19][20] Stringer describes how he considers the original Multiregional hypothesis to have been modified over time into a weaker variant that now allows a much greater role for Africa in human evolution, includinganatomical modernity (and subsequently less regional continuity than was first proposed).[21] Stringer distinguishes the original or "classic" Multiregional model as having existed from 1984 (its formulation) until 2003, to a "weak" post-2003 variant that has "shifted close to that of the Assimilation Model".[22][23] Genetic studies The finding that "Mitochondrial Eve" was relatively recent and African seemed to give the upper hand to the proponents of the Out of Africa hypothesis. But in 2002, Alan Templeton published a genetic analysis involving other loci in the genome as well, and this showed that some variants that are present in modern populations existed already in Asia hundreds of thousands of years ago.[24] This meant that even if our male line (Y chromosome) and our female line (mitochondrial DNA) came out of Africa in the last 100,000 years or so, we have inherited other genes from populations that were already outside of Africa. Since this study other studies have been done using much more data (seePhylogeography ). Fossil evidence Morphological clades Proponents of the multiregional hypothesis see regional continuity of certain morphological traits spanning the Pleistocene in different regions across the globe as evidence against a single replacement model from Africa. In general, three major regions are recognized: Europe, China, and Indonesia (often including Australia).[25][26][27] Wolpoff cautions that the continuity in certain skeletal features in these regions should not be seen in a racial context, instead calling them morphological clades; defined as sets of traits that "uniquely characterise a geographic region".[28] According to Wolpoff and Thorne (1981): "We do not regard a morphological clade as a unique lineage, nor do we believe it necessary to imply a particular taxonomic status for it".[29] Critics of multiregionalism have pointed out that no single human trait is unique to a geographical region (i.e. confined to one population and not found in any other) but Wolpoff et al. (2000) note that regional continuity only recognizes combinations of features, not traits if individually accessed, a point they elsewhere compare to the forensic identification of a human skeleton: Regional continuity... is not the claim that such features do not appear elsewhere; the genetic structure of the human species makes such a possibility unlikely to the extreme. There may be uniqueness in combinations of traits, but no single trait is likely to have been unique in a particular part of the world although it might appear to be so because of the incomplete sampling provided by the spotty human fossil record. Replica of Sangiran 17 Homo Combinations of features are "unique" in the sense of being found in only one region, or erectus skull from Indonesia more weakly limited to one region at high frequency (very rarely in another). Wolpoff showing obtuse face to vault stresses that regional continuity works