The scientific community now generally agrees that between 5 and 8 million years ago there lived in Africa a hominoid which would ultimately give rise to the first hominids and later the members of the genus Homo. This period of time was during the end of the Miocence epoch, during which a drying period enveloped equatorial Africa. As a result of this drying, the Miocene forest began to shrink, forcing the apes living in the Miocene forest to begin to make the transition to a terrestrial way of live. Many of the genera of apes at the time likely became extinct during the transition, and those that made the transition to terrestrial life survived. The early apes that began to live on the emerging African savannah likely retained their aboreal abilities, being active on the savannah during the day to return to the trees at night. From at least one of these early terrestrial apes would evolve humankind as it is today.

Fossil evidence now indicates that the major event in the evolution of hominids from that point was not the immediate development of intelligence, which was thought in the Piltdown man hoax days. Rather, the single development which set hominids apart from our ape-like ancestors was the development of bipedality: an upright, two-legged walking style. This is shown simply by looking at the fossil record. The oldest known hominid, Ardipithecus ramidus, is dated at 4.4 million years and is a recent discovery, announced in September 1994. Although most remains so far are skull fragments (a skeleton which is 45% complete has been found but not been published on yet), indirect evidence suggests that it was possibly bipedal, but still having aboreal-dwelling characteristics.

The next genus in the line of human evolution wass Australopithecus, which was definitely bipedal. The earliest known species of this genus is also a very recent discovery, being named in 1995, and is A. anamensis. It is dated to around 4.2 million years old, showing a very humanlike tibia, fibula, and humerus, although having a small and ape-like cranium. A. anamensis almost certainly represents the true beginnings of the human line and solidly shows that bipedality developed before greater intelligence.

 There are several models explaining why bipedality developed. Russell Tuttle, an anatomist and paleoanthropologist and the University of Chicago, has proposed that the earliest hominids who walked erect were in fact tree-dwelling primates who descended to the ground when the Miocene forest began to shrink, and those who were able to walk erect survived. Owen Lovejoy, on the other hand, argues that with the shrinking of the Miocene forest, the early forms of pseudo-hominids lived in the trees at night and were active on the savannah during the day. To carry food back that it would have found, it would have needed to be able to use its hands, thus encouraging bipedality. Whatever the cause of bipedality, it eventually led to the development of higher intelligence. Darwin's theory is that with the freed up hands that bipedality allows, hominids would be able to use tools, and the use of tools led to the development of greater intelligence.

The next hominid in the evolutionary line is A. afarensis, which existed between 3.9 and 3.0 million years agos. Afarensis had an apelike face with a low forehead, a bony ridge over the eyes, a flat nose, and no chin. They had protruding jaws with large back teeth, and their cranial capacity varied from 375 to 500 cc. Although the jaws and teeth are shaped between that of modern apes and humans, the pelvis and leg bones far more closely resemble those of modern man, leaving no doubt that they were bipedal. They were still slightly suited for trees, having longer and curved fingers and toes, but most scientists consider this to be evolutionary baggage. The type specimen for A. afarensis was discovered by Mary Leakey and is about 3.75 million years old. The most well known member of the species, however, is Johanson and White's Lucy, who shows that at 3 million years hominids were completely bipedal. Her teeth were obviously in a transition stage between ape and human as well. Many other A. afarensis finds in the Hadar region of Ethiopia by Johanson and White contribute to the knowledge of the species. Also, afarensis is where the Laetoli footprints come in, because it was that species to which the footprints are attributed.

Between 2 and 3 million years ago A. africanus appeared and was very similar to A. afarensis. The body size of africanus was slightly greater, as well as brain size, but the teeth and jaws were more similar to those of humans. The main fossil for this species is the "Taung baby" found by Raymond Dart in 1924. It consists of almost a full skull, the skull of an infant. A. afarensis and africanus are known as gracile australopithecines becuase of their light build. There are more robust Australopithecines as well.

A. robustus was similar to africanus, except with a larger and more robust skull and teeth. It existed between 2 and 1.5 million years ago. The average brain size is about 530 cc, and likely had a vegetarian diet due to its large grinding teeth. This species is not in the direct human lineage, but is rather a side branch that perhaps led to modern apes.

A. boisei, once known as Zinjanthropus boisei, was also a robust australopithecine and was very similar to robustus. It existed between 2.1 and 1.1 million years ago and has a brain size similar to that of robustus. Although once thought to be by Louis Leakey, A. boisei is not in the human lineage either.

 So when did Homo arise, and what species of Australopithecines led to it? These questions are extremely controversial and are still not solidly resolved. Currently, one main interpretation is that A. afarensis was the link the the Homo genus, another that A. africanus led to Homo, and a third that Homo developed side by side with afarensis and africanus, arising from another species. Currently, evidence points to africanus as the link, but the truth is still being debated.

At this point in history (between 1.5 and 3 million years ago), there was a time in which 4 or 5 hominids likely were contemporaneous; it can be thought of as the great human experiment, with the result being a branching off of the human line. The first Homo likely lived alongside Australopithecines of several species. However, even this first Homo is being challenged - Homo habilis is said by some to be a form of australopithecine. However, the main thing that gives habilis its status is that evidence of tools have been found with him, hence its name, translated as "the human with ability". Habilis existed between 2.4 and 1.5 million years ago. The species is still primitive looking, but the teeth are smaller and the brain size is much larger thatn in australopithecines at 650 cc. The brain shape is also more humanlike and he likely was capable of rudimentary speech. The picture shown is of skull 1470, the most complete habilis skull ever found, found by Richard Leakey's team at Koobi Fora. Incidently, the stone tools made by habilis were a dramatic departure from what earlier hominids were able to do. This archaeological tradition, found in East and South Africa, is often known as the Olduwan Industry because many of the primitive stone tools found at Olduvai Gorge by Louis Leakey belonged to habilis. These tools were made by striking two pebbles together, leaving a crude edge along the fracture lines of the stone. The more advanced tools of the Olduwan industray, such as Chellean hand-axes, however, were the product of a more advance level of hominid, Homo erectus

Most paleontologists now believe that a second evolutionary pulse occurred around 1.9 million years ago that produced hominids with much larger brains, Homo erectus. were the first hominids to not just be human-like, but human. They were hunters, speculates Milford Wolpoff of the University of Michigan, and likely had the ability of some sort of speech, due to an enlarged Broca's area on their skulls. The face has protruding jaws, no chin, thick brow ridges, and a brain size ranging from 750 to 1225 cc. The skeletons are more robust than those of modern humans. Erectus likely had a very efficient walking style, and probably used fire as well. In addition, their stone tools are much better than those of habilis. Some of the most famous early archaeological finds were skeletal remains of Homo erectus, including the 1893 discovery "Java Man", the "Heidelberg Marn", the "Peking Man", and the "Turkana Boy" shown in the picture on the right. Erectus also turned out to be the creater of many of the stone tools and Chellean handaxes found at the Olduvai site by the Leakeys, the so-called "Chellean Man". Erectus was likely the first hominid to spread across the world, as the migrated to China by 800,000 years ago and to Europe by 500,000. However, by 300,000 years ago they were to be replaced by a new hominid - Homo Sapiens.

There were several different types of this species that appeared onto the scene about 300,000 years ago, and perhaps the best known of this type is the emergence of Homo sapiens neanderthalensis, which represent the final stage of human evolution prior to the reduction of the Mid-Pleistocene face and refinement of anatomy to result in modern Homo sapiens about 100,000 years ago. The Neanderthal is similar to erectus except having a larger brain of around 1,500 cc, slightly larger than modern humans. The tools they made in what is called the "Mousterian tradition" are more sophisticated than those of previous humans. They also bury their dead, something no earlier hominid ever did. There exists a huge debate today about whether or not Neanderthals are in the direct human line or a side branch because a very negative view exists about the Neanderthals. Due to some very poor early descriptions of skeletons, they are thought to be hunchbacked bent-legged animal-like idiots, but they were actually much more sophisticated than that (of course not as sophisticated as modern humans). What is certain, however, is that around 120,000 years ago at least, the modern Homo sapiens sapiens first appeared and lived contemporaneously with the Neanderthal for at least 90,000 years until the Neanderthal disappeared 30,000 years ago. Modern humans have an average brain size of 1350 cc, with a sharply rising forehead, small eyebrow ridges or absent ones, a prominent chin, and a very gracile skeleton (although Texas Aggies may resemble a more Neanderthal looking version, being very robust with large eyebrow ridges). With the emergence of modern humans, tool kits became extremely sophisticated and cave paintings appeared in an advanced form. Cro-Magnon man is an example of modern human, living in Europe between 35,000 and 10,000 years ago, and was virtually identical to modern man, being skilled hunters, toolmakers, and cave artists.

 Within the last 100,000 years, a trend has existed towards smaller molars and decreased robustness. Thus, evolution has been ongoing, even within our species.

 Thus, it can be seen that Africa is truly the "cradle" of human life, being the major location for the transformation of hominids from early tree-dwellers to modern humans. Through archaeology, paleontology, taphonomy, and modern dating methods, archaeological discoveries are able to reveal to some extent the evolutionary trends and actions that have transpired over the past five million years. However, due to the inherent limitations to the Linnean classification system, such as where to draw the lines between species and genera, many debates still exist as to the relationship between different hominids, such as whether A. afarensis is the common ancestor between man an ape or A. africanus. However, new techniques and discoveries appear every day, so the future of African archaeology looks exciting and informative.

• African Archaeology Front Page
• The Evidence: Hominid Fossils
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