Anatomically modern human

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In paleoanthropology, anatomically modern humans (AMH) is a term used to distinguish Homo sapiens as having an anatomy consistent with the range of phenotypes seen in contemporary humans from varieties of extinct archaic humans.

Homo sapiens evolved from "archaic" or "robust" predecessors (Homo heidelbergensis, or a related offshoot from Homo erectus) around 315,000 years ago. The divergence of modern human populations dates to shortly after this time, the oldest division being that of the hunter-gatherer populations of Southern Africa, although there have been numerous events of admixture both among modern populations and between modern and archaic ones.

Behavioral modernity, involving the development of language, figurative art and early forms of religion (etc.) is taken to have arisen before 40,000 years ago, marking the beginning of the Upper Paleolithic (in African contexts also known as the Later Stone Age).

Video Anatomically modern human

Nomenclature and classification

The binomial name for the taxonomic species of the contemporary human population is Homo sapiens sapiens. The species is taken to have emerged from a predecessor within the Homo genus around 200,000 to 300,000 years ago.

The term "anatomically modern humans" (AMH) is used with varying scope depending on context, to distinguish "anatomically modern" Homo sapiens from archaic humans such as Neanderthals. In a convention popular in the 1990s, Neanderthals were classified as a subspecies of H. sapiens, as H. s. neanderthalensis, while AMH (or European early modern humans, EEMH) was taken to refer to "Cro-Magnon" or H. s. sapiens. Under this nomenclature (Neanderthals considered H. sapiens), the term "anatomically modern Homo sapiens" (AMHS) has also been used to refer to EEMH ("Cro-Magnons"). It has since become more common to designate Neanderthals as a separate species, H. neanderthalensis, so that AMH in the European context refers to H. sapiens (but the question is by no means resolved).

In this more narrow definition of Homo sapiens, the subspecies H. s. idaltu, discovered in 2003, also falls under the umbrella of "anatomically modern". The recognition of Homo sapiens idaltu as a valid subspecies of the anatomically modern human lineage would justify the description of contemporary humans with the subspecies name Homo sapiens sapiens.

A further division of AMH into "early" or "robust" vs. "post-glacial" or "gracile" subtypes has since been used for convenience. The emergence of "gracile AMH" is taken to reflect a process towards a smaller and more fine-boned skeleton beginning around 50,000-30,000 years ago.

The following is a list of human varieties which lived after 200 kya with their classification within the "modern"/"archaic" scheme

Maps Anatomically modern human

Anatomy

General build

Generally, modern humans are more lightly built than archaic humans from which they have evolved. Humans are a highly variable species; modern humans can show remarkably robust traits, and early modern humans even more so. Despite this, modern humans differ from archaic people (the Neanderthals and Denisovans) in a range of anatomical details.

Braincase anatomy

The cranium lacks a pronounced occipital bun in the neck, a bulge that anchored considerable neck muscles in Neanderthals. Modern humans, even the earlier ones, generally have a larger fore-brain than the archaic people, so that the brain sits above rather than behind the eyes. This will usually (though not always) give a higher forehead, and reduced brow ridge. Early modern people and some living people do however have quite pronounced brow ridges, but they differ from those of archaic forms by having both a supraorbital foramen or notch, forming a groove through the ridge above each eye. This splits the ridge into a central part and two distal parts. In current humans, often only the central section of the ridge is preserved (if it is preserved at all). This contrasts with archaic humans, where the brow ridge is pronounced and unbroken.

Modern humans commonly have a steep, even vertical forehead whereas their predecessors had foreheads that sloped strongly backwards. According to Desmond Morris, the vertical forehead in humans plays an important role in human communication through eyebrow movements and forehead skin wrinkling.

Jaw anatomy

Compared to archaic people, anatomically modern humans have smaller, differently shaped teeth. This results in a smaller, more receded dentary, making the rest of the jaw-line stand out, giving an often quite prominent chin. The central part of the mandible forming the chin carries a triangularly shaped area forming the apex of the chin called the mental trigon, not found in archaic humans. Particularly in living populations, the use of fire and tools require fewer jaw muscles, giving slender, more gracile jaws. Compared to archaic people, modern humans have smaller, lower faces.

Body skeleton structure

The body skeletons of even the earliest and most robustly built modern humans were less robust than those of Neanderthals (and from what little we know from Denisovans), having essentially modern proportions. Particularly regarding the long bones of the limbs, the distal bones (the radius/ulna and tibia/fibula) are nearly the same size or slightly shorter than the proximal bones (the humerus and femur). In ancient people, particularly Neanderthals, the distal bones were shorter, usually thought to be an adaptation to cold climate. The same adaptation can be found in some modern people living in the polar regions.

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Evolution

Divergence time estimates

The genus Homo emerges from australopithecine hominins some time after 3 million years ago. With the arrival of Homo erectus in the fossil record ca. 1.8 to 1.3 million years ago, cranial capacity had doubled to 850 cm³. It is believed that Homo erectus and Homo ergaster were the first to use fire and complex tools. Modern humans evolved from Homo heidelbergensis, Homo rhodesiensis or Homo antecessor and, some 100,000 to 50,000 years ago, took the place of local populations of Homo erectus, Homo denisova, Homo floresiensis and Homo neanderthalensis.

The oldest fossil remains of anatomically modern humans are the Jebel Irhoud fossils from Morocco which are approximately 300,000 years old. Other important early modern finds include the Omo remains found in modern-day East Africa, which date to 195,000 years ago and include two partial skulls as well as arm, leg, foot and pelvis bones. A 2017 analysis comparing the genome of a Stone Age Khoi-San skeleton with other modern African populations suggest that the Koi-San people diverged from the West African Mandinka people approximately 356,000 years ago, indicating the origin of modern humans is older than that date. Other fossils include the proposed Homo sapiens idaltu from Herto in Ethiopia that are almost 160,000 years old and the Skhul hominids from Israel, which are 90,000 years old. The oldest human remains from which an entire genome has been extracted belongs to Ust'-Ishim man, who lived about 45,000 years ago in Western Siberia.

Dates approximate, consult articles for details

(From 2000000 BCE till 2013 CE in (partial) exponential notation)

See also: Java Man (-1.75e+06), Yuanmou Man (-1.75e+06 : -0.73e+06),

Lantian Man (-1.7e+06), Nanjing Man (- 0.6e+06), Tautavel Man (- 0.5e+06),

Peking Man (- 0.4e+06), Solo Man (- 0.4e+06), and Pe?tera cu Oase (- 0.378e+05)

Derivation from H. erectus

The derivation of a comparatively homogeneous single species of Homo sapiens from more diverse varieties of archaic humans (all of which were descended from the dispersal of Homo erectus some 1.8 million years ago) was debated in terms of two competing models during the 1980s: "recent African origin" postulated the emergence of Homo sapiens from a single source population in Africa, which expanded and led to the extinction of all other human varieties, while the "multiregional evolution" model postulated the survival of regional forms of archaic humans, gradually converging into the modern human varieties by the mechanism of clinal variation, via genetic drift, gene flow and selection throughout the Pleistocene.

Since the 2000s, the availability of date from archaeogenetics and population genetics has led to the emergence of a much more detailed picture, intermediate between the two competing scenarios outlined above: The recent Out-of-Africa expansion accounts for the predominant part of modern human ancestry, while there were also significant admixture events with regional archaic humans.

There are now (as of 2017) assumed to have been at least two Out of Africa migrations of Homo sapiens. A first wave taking place around 130,000 and 115,000 years ago, followed by a second wave, sometimes connected with the Toba supereruption c.77,000 years ago, which followed the so-called Southern Route, along the southern coastline of Asia, resulting in the colonization of Australia around 65,000 years ago, while Europe was populated by an early offshoot which settled the Near East and Europe by around 50,000 years ago.

Within Africa, there had been a far earlier divergence between Southern African hunter-gatherers, Central African foragers, West and East African populations, going back more than 150,000 years, and possibly as far as 300,000 years. Therefore, the most genetically distinct contemporary human populations are hunter-gatherers within Southern Africa.

The ongoing admixture events within anatomically modern human populations make it difficult to give an estimate on the age of the matrilinear and patrilinear most recent common ancestors of modern populations (Mitochondrial Eve and Y-chromosomal Adam). Estimates on the age of Y-chromosomal Adam have been pushed back significantly with the discovery of an ancient Y-chromosomal lineage in 2013, likely beyond 300,000 years ago. There has, however, been no reports of the survival of Y-chromosomal or mitochondrial DNA clearly deriving from archaic humans (which would push back the age of the most recent patrilinear or matrilinear ancestor beyond 500,000 years).

Early Homo sapiens

The term Middle Paleolithic is intended to cover the time between the first emergence of Homo sapiens (roughly 300,000 years ago) and the emergence of full behavioral modernity (roughly 50,000 years ago).

Many of the early modern human finds, like those of Omo, Herto, Skhul, and Pe?tera cu Oase exhibit a mix of archaic and modern traits. Skhul V, for example, has prominent brow ridges and a projecting face. However, the brain case is quite rounded and distinct from that of the Neanderthals and is similar to the brain case of modern humans. It is now known that modern humans north of Sahara and outside of Africa have some archaic human admixture, though whether the robust traits of some of the early modern humans like Skhul V reflects mixed ancestry or retention of older traits is uncertain.

The "gracile" or lightly built skeleton of anatomically modern humans has been connected to a change in behavior, including increased cooperation and "resource transport". There is evidence that the characteristic human brain development, especially the prefrontal cortex, was due to "an exceptional acceleration of metabolome evolution ... paralleled by a drastic reduction in muscle strength. The observed rapid metabolic changes in brain and muscle, together with the unique human cognitive skills and low muscle performance, might reflect parallel mechanisms in human evolution." The Schöningen spears and their correlation of finds are evidence of complex technological skills already 300,000 years ago and are the first obvious proof for an active (big game) hunt. H. heidelbergensis already had intellectual and cognitive skills like anticipatory planning, thinking and acting that so far have only been attributed to modern man.

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Upper Paleolithic

There is considerable debate regarding whether the earliest anatomically modern humans behaved similarly to recent or existing humans. Behavioral modernity is taken to include fully developed language (requiring the capacity for abstract thought), artistic expression, early forms of religious behavior, increased cooperation and the formation of early settlements, and the production of articulated tools from lithic cores, bone or antler. The term Upper Paleolithic is intended to cover the period since the rapid expansion of modern humans throughout Eurasia, which coincides with the first appearance of Paleolithic art such as cave paintings and the development of technological innovation such as the spear-thrower. The Upper Paleolithic begins around 50,000 to 40,000 years ago, and also coincides with the disappearance of archaic humans such as the Neanderthals.

The term "behavioral modernity" is somewhat disputed. It is most often used for the set of characteristics marking the Upper Paleolithic, but some scholars use "behavioral modernity" for the emergence of H. sapiens around 200,000 years ago, while others use the term for the rapid developments occurring around 50,000 years ago. It has that the emergence of behavioral modernity was a gradual process.

In January 2018 it was announced that modern human finds at Misliya cave, Israel, in 2002, had been dated to around 185,000 years ago, the earliest evidence of their out of Africa migration.

The earliest H. sapiens (AMH) found in Europe are the "Cro-Magnon" (named after the site of first discovery in France), beginning about 40,000 to 35,000 years ago. These are also known as "European early modern humans" in contrast to the preceding Neanderthals.

The equivalent of the Eurasian Upper Paleolithic in African archaeology is known as the Later Stone Age, also beginning roughly 40,000 years ago. While most clear evidence for behavioral modernity uncovered from the later 19th century was from Europe, such as the Venus figurines and other artefacts from the Aurignacian, more recent archaeological research has shown that all essential elements of the kind of material culture typical of contemporary San hunter-gatherers in Southern Africa was also present by least 40,000 years ago, including digging sticks of similar materials used today, ostrich egg shell beads, bone arrow heads with individual maker's marks etched and embedded with red ochre, and poison applicators. There is also a suggestion that "pressure flaking best explains the morphology of lithic artifacts recovered from the c. 75-ka Middle Stone Age levels at Blombos Cave, South Africa. The technique was used during the final shaping of Still Bay bifacial points made on heat-treated silcrete." Both pressure flaking and heat treatment of materials were previously thought to have occurred much later in prehistory, and both indicate a behaviourally modern sophistication in the use of natural materials. Further reports of research on cave sites along the southern African coast indicate that "the debate as to when cultural and cognitive characteristics typical of modern humans first appeared" may be coming to an end, as "advanced technologies with elaborate chains of production" which "often demand high-fidelity transmission and thus language" have been found at Pinnacle Point Site 5-6. These have been dated to approximately 71,000 years ago. The researchers suggest that their research "shows that microlithic technology originated early in South Africa, evolved over a vast time span (c. 11,000 years), and was typically coupled to complex heat treatment that persisted for nearly 100,000 years. Advanced technologies in Africa were early and enduring; a small sample of excavated sites in Africa is the best explanation for any perceived 'flickering' pattern." These results suggest that Late Stone Age foragers in Sub-Saharan Africa had developed modern cognition and behaviour by at least 50,000 years ago. The change in behavior has been speculated to have been a consequence of an earlier climatic change to much drier and colder conditions between 135,000 and 75,000 years ago. This might have led to human groups who were seeking refuge from the inland droughts, expanded along the coastal marshes rich in shellfish and other resources. Since sea levels were low due to so much water tied up in glaciers, such marshlands would have occurred all along the southern coasts of Eurasia. The use of rafts and boats may well have facilitated exploration of offshore islands and travel along the coast, and eventually permitted expansion to New Guinea and then to Australia.

Late Pleistocene climate change and the global expansion of ...

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References and notes

M. Anne Katzenberg, Shelley R. Saunders (eds.), Biological Anthropology of the Human Skeleton (2008)
Fred H. Smith, James C. Ahern, The Origins of Modern Humans: Biology Reconsidered (2013).

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External links

General information

Lev A. Zhivotovsky, Noah A. Rosenberg, and Marcus W. Feldman "Features of Evolution and Expansion of Modern Humans, Inferred from Genomewide Microsatellite Markers" Am. jr. of Human Genetics, May 2003; 72(5), pp 1171-1186. [1]
Early And Late "archaic"homo Sapiens And "anatomically : Modern" Homo Sapiens. hawaii.edu.
Keith L. Hunley, Meghan E. Healy, and Jeffrey C. Long: "The global pattern of gene identity variation reveals a history of long-range migrations, bottlenecks, and local mate exchange: Implications for biological race" American Journal of Physical Anthropology: Special Issue: Race Reconciled: How Biological Anthropologists View Human Variation Volume 139, Issue 1, pages 35-46, May 2009 [2]
Origins of Modern Humans: Multiregional or Out of Africa? actionbioscience.org
homo erectus tool use and adaptation. public.wsu.edu.
Early Human Evolution: Early Human Culture; Early Modern Homo sapiens. palomar.edu.
Human Timeline (Interactive) - Smithsonian, National Museum of Natural History (August 2016).

Museums of Natural History

Species; Human Family Tree. si.edu. The Smithsonian Institution's Human Origins Program
Meet our early human family. nhm.ac.uk.
Homo sapiens. mnsu.edu

Source of article : Wikipedia

Wednesday, March 28, 2018