Evolution

The Evolution of Early Man



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"The Evolution of Early Man"
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Three and a half million years ago two of our ancestors walked across a field of damp volcanic ash, not realizing that they were achieving a kind of immortality. This occurred in East Africa in what is now Tanzania in a place called Laetoli. Although their brains were still small what made them hominids was bipedal locomotion-they walked upright, and thus were no longer apes.
Why did our ancestors stand up? By 3.5 million years ago the Ice Age had caused a global shift in weather, which precipitated the disappearance of vast forested areas in Africa, eventually replaced by grasslands, the savannah. An upright posture enabled early man to see much greater distances in the new environment. It freed their hands for food gathering, hunting and caring for offspring. Walking is also much more efficient than moving on all fours, certainly over long distances. It may have rendered them more imposing to an enemy or predator. Finally, a vertical posture subjects one to much less heat radiation from the sun than a horizontal one.
Sometime between 5 and 7 million years ago our common ancestor branched off from the apes in an evolutionary divergence. The earliest known biped is Sahelanthropus tchadensis, whose spectacularly preserved cranium was found in Chad and was nicknamed Toumai by its discoveres. It's brain size was 350cc, the same as a chimpanzee(Normal human brains are around 1400cc). The face was flatter and more human like, very unlike a chimpanzee.
Next in line came Orrorin tugenensis, 6 million years ago, from the Tugen Hills of northwestern Kenya, also known as Millennium Man. The main evidence identifying it as hominid was the humanlike way its femur connected to the pelvis, evidence of its ability to walk.
Between 4.5 and 5.8 million years ago Ardipithecus kadabba and ramidus shared a desert region of present day Ethiopia. The toe bone and teeth are similar to humans. There is evidence that this hominid lived in a forest environment.
Australopithecus anamensis consists of nine fossils from Kenya dated 3.9-4.2 mya. They include a very humanlike humerus, while the jaw and teeth are still ape-like.
The creature that left the famous footprints was most likely Austalopithecus afarensis, the southern ape of Afar, a region in Ethiopia, where a group of thirteen individuals, 9 adults and 3 children, were discovered at a site where they probably died together. From this "First Family" came the famous Lucy, so named by her discoverer, David Johanson, after the famous Beatles song. They date to between 3-3.9mya. 45% of Lucy's skeleton was intact-she was tiny, only three and a half feet tall, with long arms, ape-like facial features and a brain size in the 400cc range, but hands quite modern in appearance, and of course, bipedal. Large molars suggest a coarse, gritty diet, typical of a grassland environment.
Around 3 million years ago a different hominid appeared-Australopithecus africanus, The jaw and teeth are closer to human and the face less prognathous (a forward ape-like thrust), the body longer and taller than Lucy. The smaller teeth suggests more of a meat diet. The original find was made by Raymond Dart in 1925 at the Taung site in South Africa.
Between 2.2 and 4.4 mya two bipeds appeared-Austalopithecus robustus and boisei, with a slightly larger brain but, more significantly, powerful cranial architecture, specifically a thin ridge of bone atop the skull, called the sagittal crest, which made for much larger and stronger temporalis chewing muscles. They also sported huge molars due to a diet of nuts and seeds. And they themselves were part of the food chain-one robustus skull had a pair of holes that exactly match a leopard's lower canine teeth. They disappeared from the fossil record by 1 million years ago.
Another dramatic appearance occurred in the evolutionary story around 2.4mya-Homo habilis, with a more rounded head and larger brain(700cc) this "Handy Man' was the first known species of our genus, Homo. The inside of the cranium shows evidence of Broca's area, the source of speech.
Even more importantly Homo habilis is regarded as the very first tool maker, for here began the Oldowan tool industry, first recognized by the famous paleoanthropologist team of Louis and Mary Leakey in Olduvai Gorge. Tools produced consisted of crude choppers and scrapers, but also the waste flakes struck off form the artifacts, to be used in butchering.
These tools heralded the dawn of the Paleolithic, which lasted until 10,000 BC.
And then came Homo erectus, 1.8mya-longer, leaner, and possibly meaner. With better technology, big-game hunting, mastery of fire and an urge to move erectus literally conquered the world. He was in Eastern Europe by 1.75mya, China 1.6mya, and Spain by 800,000 thousand ya. Cranial capacity averaged 960cc. The skull had a more modern configuration, the occipital region rounder and asymmetry in the brain's structure, similar to ours. Nasal bones indicate the first projecting nose, rather than inset, ape-like nostrils. Some adults were nearly 6ft and about as heavy as ourselves. With a cap and contemporary attire this hominid could sit in a Starbucks and not attract any undue attention.
A new tool industry appeared with erectus, the Acheulian, featuring hand-axes, cleavers, scrapers and flakes, more symmetrical and aesthetic than the Oldowan, although these two coexisted far into the Paleolithic.
All of this brought dramatic changes in early man's adaptive strategies. At Torralba and Ambrona in Spain are remains of perhaps ten different hunts, consisting of 55 elephants, 26 horses, 25 deer and 10 cattle, all suggesting a high degree of cooperation and ability to plan and coordinate complex tasks.

By 300,000ya archaic forms of Homo sapiens were appearing in Europe, Africa and Asia with a new tool industry called Levallois that produced more refined weapons and tools.
Homo neanderthalensis can be traced back to this time but the classic Neandertal s date from 130,000 to 30,000 ya. Their cranial capacities averaged 1450cc. They had heavy brow ridges, sloping foreheads, projecting face and no chin to speak of. They were big, with squat torsos and short extremities, designed for Ice Age cold. The size of their shoulder blades, collarbones and forearms indicate massive muscles and tremendous upper body strength, while hand anatomy shows they were capable of an incredibly strong "power grip". A formidable adversary. And probably the most effective hunters that ever lived.
They were also the first people to systematically bury their dead, often with grave goods that included tools, food, stone pillows and flowers. In other words, Neandertals seem to show compassion for their fellow man.

It is likely that fully modern man evolved in Africa between 100,000 and 200,000 ya, and then spread out into Asia and Europe to replace premoderns wherever they came into contact through competitive exclusion. At 40,000 ya there was a flowering of art and great innovation in tool making. The change was spectacular and you only have to visit the many cave art localities in France and Spain to see the evidence. Non-utilitarian objects became abundant as well as elaborate burials and larger, more sedentary settlements.
Modern man had arrived.

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