Anatomically modern human (AMH) or
early modern human in
paleoanthropology refers to early individuals of
Homo sapiens with an appearance similar to that of modern humans.
Anatomically modern humans evolved from
archaic Homo sapiens in the
Middle Paleolithic, about 200,000 years ago. The emergence of anatomically modern human marks the dawn of the subspecies
Homo sapiens sapiens, i.e. the subspecies of
Homo sapiens that includes all modern humans. The oldest fossil remains of anatomically modern humans are the
Omo remains that date to 195,000 years ago. Other fossils include
Homo sapiens idaltu from Herto in Ethiopia that are 150
kya and remains from
Skhul in Israel that are 90kya.
Anatomy
thumb|right|460px|Anatomical comparison of the Skulls of anatomically modern humans and Homo neanderthalensis Anatomically modern humans are distinguished from their immediate ancestors, archaic homo sapiens, by a number of anatomical features. Archaic homo sapiens had robust skeletons, indicating that they lived a physically demanding life; this may mean that anatomically modern humans, with their more
gracile frames, had become more dependent on technology than on raw physical power to meet the challenges of their environment. Archaic homo sapiens also had very prominent
brow ridges (protruding layers of bone above the
eye socket). With the emergence of anatomically modern humans, the brow ridges had significantly reduced, and in modern humans they are, on average, barely visible. Another distinguishing feature of AMH is a prominent chin, something which is lacking in archaic homo sapiens.
AMH also have a vertical
forehead whereas their predecessors had foreheads that sloped backwards. According to
Desmond Morris, the vertical forehead in humans not only houses larger brains, but the prominent forehead plays an important role in human communication through
eyebrow movements and forehead skin wrinkling.
Early modern humans
thumb|right|250px| Skhul V exhibiting a mix of archaic and modern traits
The
Omo,
Hertho,
Skhul and
Jebel Qafzeh remains are sometimes referred to as "Early Modern Humans" because their skeletal remains exhibit a mix of
archaic and modern traits. Skhul V for example, has prominent brow ridges and a projecting face. However the brain case of Skhul V is distinct from that of the Neanderthals and is similar to the brain case of modern humans.
In Europe, the early modern humans were the
Cro-Magnon.
Origins of modern humans
As it is usually presented, there are two major competing models on this subject -
Recent African origin and
Multiregional evolution. The debate concerns both the
relative amount of replacement or interbreeding which occurred in areas outside of Africa, when waves of humans (or human ancestors) left it to colonize other areas, and the relative importance of more recent waves as opposed to more ancient ones.
The mainstream view, known as the
recent African origin model, holds that all or nearly all modern human genetic diversity around the world can be traced back to the first anatomically modern humans to leave Africa. This model is supported by multiple and independent lines of evidence, such as the fossil record and genetics.
Historically, critics of this view are often bracketed together as holding a "
multiregional hypothesis" which has waned in popularity since the early 1990s. Such critics argue that significant amounts of older non-African genetic lineages have survived in various parts of the world through inter-breeding with anatomically modern humans. According to strong versions of the multiregional model the various human populations around the world today will have surviving genetic material which goes back even as far as early hominids such as
homo erectus. More commonly, admixture with much later
archaic homo sapiens, such as
Neanderthals is proposed. While proponents of Out of Africa theory cannot rule out admixture between humans of sub-Saharan African origin and all archaic
homo sapiens,
several recent studies on the Neanderthal's genome indicate that humans and Neanderthals failed to produce crossprogeny capable of effectively reproducing (i.e. they either failed to interbreed or the progeny they produced did not survive or reproduce well)
.
In practice, controversy is generally about specific periods and specific proposals for periods of such interbreeding. The existence and importance of these waves out of Africa is generally accepted, while the
possibility of at least a small level of inter-breeding between recent sub-Saharan arrivals and their less 'modern' contemporaries at various stages of prehistory is not particularly controversial.
Modern human behavior
There is considerable debate regarding whether the earliest anatomically modern humans behaved similarly to recent or existing humans. Modern human behaviors characteristic of recent humans include fully modern language, the capacity for abstract thought and the use of symbolism to express cultural creativity. There are two opposing hypotheses regarding the origins of modern behavior. Some scholars argue that humans achieved anatomical modernity first, around 200kya, and only later did they adopt modern behaviors around 50kya. This hypothesis is based on the limited record of fossils from periods before 50kya and the abundance of human artifacts found after 50kya. Proponents of this view distinguish "anatomically modern humans" from "behaviorally modern humans".
The opposing view is that humans achieved anatomical and behavioral modernity simultaneously. For example, proponents of this view argue that humans had evolved a lightly built skeleton during the transition to anatomical modernity, and this could have only occurred through increased human cooperation and the increased use of technology, traits characteristic of modern behavior.
See also
