Anatomically Modern H. sapiens
The first anatomically modern H. sapiens
appear in the fossil record soon after 100,000 years ago. They are much
more gracile than earlier groups (e.g., Neandertals and other archaics)
and share a number of physical characteristics with modern human
populations, including:
- smaller face, with prominent chin
- rounded skull
- increasingly gracile postcranial morphology
 |
Interaction between Neandertals and anatomically modern humans (AMH) has been suggested on the basis of findings in the Levant (Middle East). Two of the oldest AMH sites - Skhul and Qafzeh - were discovered in close spatial (and overlapping temporal) proximity to Neandertal sites (Tabun, Amud, and Kebara). However, it remains uncertain what type of real interaction - if any - occurred between the groups.
Upper Paleolithic
Upper Paleolithic technology, culture, and behavior begins to appear in the archaeological record sometime after 45 kyr. Some of these differences include:- larger, more elaborate (specialized) tool kit
- use of bone, antler, and other materials, in addition to stone
- production of ornamental artifacts
- construction of elaborate shelters
- increased use of exotic (non-local) raw material in toolmaking
The first anatomically modern humans found in Europe were called the Cro Magnons (general cranial traits pictured above). While the individuals found at Cro Magnon in particular were not the earliest inhabitants of Europe, it appears as though people very similar to the Cro Magnons precipitated the sudden disappearance of Europe's previous inhabitants, the Neandertals; though, once again, the actual nature of these events remains a mystery.
Upper Paleolithic technologies spread to many regions, including Australia, by 45 kyr. Upper Paleolithic technology is not found in southern Asia until many years later (at about 12 kyr). It remains a possibility that undiscovered sites exist in the region, since Upper Paleolithic industries inevitably passed through the region. However, crude stone tools remain common in southern Asia, and recent redating of H. erectus fossils on Java suggest that they may have existed isolated on the island until as recent as 27 kyr.
Modern Behavior
Modern humans utilizing Upper Paleolithic technology continued to live in a manner not unlike that of Neandertals; however, they were able to exploit a wider range of resources and different environments. This technological advantage is expected to have manifested itself in the demographics of Upper Paleolithic cultures:- Upper Paleolithic modern humans lived at much higher population densities than Neandertals
- they also lived longer than Neandertals
- they incurred fewer instances of injury and disease
What then, is the basis of this sudden modernization which became such a successful strategy for modern humans? One argument suggests that the change began at the genetic level, creating a biological template that facilitated modern behavior. These changes would be indubitably cognitive in nature, and are not likely to materialize in the fossil record. However, another argument suggests that the human revolution came as a result of cultural evolution, and that the hiatus between the emergence of anatomically modern humans and the "appropriate" behavior was merely a period of cultural development and accumulation.
Origin of Anatomically Modern Humans -- Two Models
Two main models have been emerged two address the emergence of anatomically modern humans, although there are other models that borrow from both extremes. One is the Replacement model, often referred to as "Out of Africa", and the other is the Multiregional model. The main question that both of these models address concerns the manner in which modern humans emerged. As explained in the previous chapter, the first hominids to migrate from Africa did so nearly 1.8 million years ago; additionally, other populations of archaics and anatomically modern humans undoubtedly migrated to and fro. So when the behaviorally modern humans left Africa, did they emerge as a single unit and spread throughout the world? Also, when these groups contacted existing groups (e.g., Neandertals, H. erectus), did these populations experience gene flow through interbreeding, or was there a population replacement? The Multiregional Model |
 The Replacement Model |
The replacement model argues for no gene flow or interbreeding, and offers some genetic evidence for this claim. Because of relative homogeneity in the human genome, as well as a lack of unique regional genes, geneticists argue that all modern day human beings emerged from an African population, sometime between 100 - 200 kyr ago.
If earlier populations did indeed
interbreed with modern groups, novel genes would be expected in these
regions, yet none have been found. Additionally, the lack of genetic
diversity indicates a time of very low population, possibly a bottleneck,
without sufficient time to regain variation through mutation.
Interestingly, a new fossil find has sparked heated debate once more. In
April of 1999, a subadult was discovered in Portugal that exhibited a
mixture of Neanderthal and modern human features (More information on this
find can be accessed through this
link). The skeleton is of a boy who may have been approximately 4
years old at the time of his death, and the bones are dated to about
24,500 years ago - the youngest (part) Neanderthal find to date. If the
features of this skeleton do in fact suggest that Neanderthals and modern
humans were able to interbreed, then that points to a conclusion that
Neanderthals were actually a subspecies of modern human beings, and not a
separate species, as the Replacement model indicates.
Information provided by: http://www.wwnorton.com