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Evolution                  3 Million BC
Africa
Southwest Asia
Egypt
Indus Valley
China
Europe
South America
Mesoamerica
North America
Other

In General

It is an inescapable fact of genetics that all people alive in the world are genetically related, and that at some point an individual existed whom we all claim as an ancestor. The only points of debate are how long ago that ancesor lived, and where. DNA data suggests all modern humans are genetic descendants of one small inbred group of prehistoric Africans.(18)

The "Total Replacement," "African Origins," or "Eve" model contends that modern humans evolved first and only in Africa and only a few hundred thousand years ago or less, and then migrated to the rest of the world, displacing all other hominid forms, and with little or no genetic interchange between them. If this is true, then, as interesting as those many European and Asian fossils and sites of hundreds of thousands of years ago are, the people who left these remains had almost nothing to do with us in terms of our physical or cultural heritage. This is a difficult premise for many anthropolgists to accept, because so much of what we know about human evolution has been based on sites such as Zhoukoudian, in China, Toralba-Ambrona, in Spain, etc.

Alternatively, the "Multiregional Evolution," "Continuity," or "Candelabra" models propose that: sometime between about 1 million and 2 million years ago a generic Homo ancestor or ours spread out across the warmer latitudes of Africa, the Middle East, Asia, and possibly the southernmost fringe of Europe; then, with the passage of the millennia, although these groups began to diverge somewhat as they adapted to local and different environments, across the whole range of Homo they were evolving toward Homo spaiens as a result of gene flow that connected all human groups to some extent and because they were all under similar evolutionary selective forces as genralized hunter-foragers; so they all converged at about 30,000 years ago as one species, Homo sapiens--but with the physical differencess that distinguish modern Europeans from, for example, modern Chinese.(18)

This "African Eve Hypothesis" is based on the study of DNA taken from the mitocondria, which are features in human cells where energy to keep the cell functioning is produced.(18)

On perhaps two occasions in the past the human lineage split into separate species, as distinct as wolves and coyotes. The most recent such occasion may have been at the time of the Great Leap Forward. The earlier such occasion was around three million years ago, when our lineage split into two: a man-ape with a robust skull and very big cheek teeth, assumed to eat coarse plant food, and often referred to as Australopithecus robustus (meaning "the robust southern ape"); and a man-ape with a more lightly built skull and smaller teeth, assumed to have an omnivorous diet, and known as Australopithecus africanus ("the southhern ape of Africa"). The latter man-ape evolved into a larger-brained form termed Homo habilis ("man the handyman"). However, fossil bones that some paleontologists consider to represent male and female Homo habilis differ so much from each other in skull size and tooth size that they may actually imply another fork in our lineage yielding two distinct habilis-like species: Homo habilis himself, and a mysterious "Third Man." Thus, by two million years ago there were at least two and possibly three protohuman species. (114)

The third and last of the big changes that began to make our ancestors more human and less apelike was the regular use of stone tools. This is a human hallmark with clear animal precedents: woodpecker finches, Egyptian vultures, and sea otters are among the other animal species that evolved independently to employ tools in capturing or processing food, though none of these species is as heavily dependent on implements as we now are. Common chimpanzees also use tools, occasionally of stone, but not in numbers sufficient to litter the landscape. But by around 2 1/2 million years ago very crude stone tools appear in numbers in areas of East Africa occupied by the protohumans. Since there were two or three protohuman species, who made the tools? Probably the light-skulled species, since both it and the tools persisted and evolved. (114)

In a typical modern chronology, the line that would lead to us split off from Old World Monkeys about 25 million years (m.y.) ago; from the gibbons, 18 m.y. ago; from orangutans around 14 m.y. ago; from gorillas some 8 m.y. ago; and from the chimps approximately 6 m.y. ago. Bonobos and common chimps went their separate ways only about 3 m.y. ago...(119)

There is now general consensus that there were at least four broad categories of hominid that emerged after the split from the ancient chimpanzee lineage - although any new discovery has the potential to change this. The evolutionary pathway appears to have led first from a common ancestor with the chimpanzee to the genus Ardipithecus between four and five million years ago and then to the gracile australopithecines before the emergence of the robust australopithecines and our own genus Homo, approximately 2.5 million years ago. (142)

At the beginning of the 1990s, there were about eight species of hominid known to have existed between five million years and one million years. Today, we recognize no less than 13 early hominid species, and the numbers of "new" species will grow as the science progresses. (142)

Africa

Paleoanthropologists recognize various species of early hominids in the period between about 4 and 1 million years ago. A substantial number of scholars accept at least four of these species: Australopithicus afarensis, Australopithicus africanus, Australopithicus robustus, and Australopithicus boissei. Several factors identify them as probable members of the same genus: 1) they are all bipedal, walking upright on two legs all or most of the time; 2) they all appeared to have brains only slightly larger, if at all, than modern gorillaas and chimps; 3) they all lived in Africa; and 4) they all had teeth that looked somewhat like ours and differed from those of girillas and chimps in various details.(6)

The most famous ancient footprints, made some 3.5 million years ago, were left by two adults and a child, presumably members of the Australopithecus afarensis species, who walked across a plain now known as Laetoli in Tanzania. The long track of prints was discovered in the late 1970s by an expedition led by Dr. Mary Leakey, the noted Kenyan fossil hunter. The prints provided further evidence that human ancestor species were walking upright long before they started making stone tools. (75)

The earliest tool users whose physical remains we have found left their lithic handiwork at Kada Gona, Ethiopia, about 2.6 million years ago and slightly later at other sites in the Hadar country and around Lake Turkana in northern Kenya. They were smallish creatures, more ape than human, at least to the casual eye, and they had brains about a third the size of ours. However, in the ratio of brain volume to body mass, they were the smartest land mammals of their time. (130)

A remarkable window into this evolutionary adaptation is being studied at the world famous Sterkfontein site west of Johannesburg in South Africa. There, in a cave deposit known as Member 4, is evidence of a speciation event: fossils of one species exhibiting a shift in morphology that eventually turns them into another species. The speciation window at Sterkfontein has been dated to between 2.8 and 2.6 million years ago, fairly soon after the intensification of global cooling. The individual africanus specimens recovered there show an astounding anatomical variation, the implications of which are still being considered. It would appear that africanus - through the development of bigger teeth and more humanlike physiology - is being transformed either into the robust ape-man form or into true humans - or both! Although it is premature to speculate on what we will eventually make of these fossils, there is a very real possibility that a transition from ape-man to human occurred in southern Africa. (142)

Africanus had a massively built upper body with long arms, and yet its lower limbs resembled in relative size and length those of a chimpanzee. A different kind of biped than Lucy. I was thunderstruck. This observation flew in the face of everything that I had been taught, not only about the species but about the whole story of early human evolution. Long arms and short legs! There was no denying that africanus' skeleton in its proportions looked far more primitive than that of afarensis. Yet africanus' skull was more "modern" than that of afarensis. In conventional evolutionary terms this was nonsensical. How could a species of hominid advance from the neck upward while the rest of the body regressed into a more ape-like form? I could reach only one logical answer. Afarensis could not be the mother species of africanus. They must have a common ancestor - one that had yet to be discovered - that had afarensis' skull, or something like it, and something akin to africanus' body, in which case they would only be sister species. (142)

Eventually, my database was large enough that I was convinced that africanus was proportioned more like an ape. Furthermore, I had come to realize that it was not just a matter of mass differences, but the actual relative limb lengths of africanus were more like those of a chimpanzee than those of a human. Africanus was built pretty much like a bipedal nonhuman ape. It was becoming very clear that there were two completely different regional evolutionary patterns emerging. The East African one was distinguished by the early hominids having ape-like skulls and very humanlike limb proportions at an early stage in their evolution. Then in South Africa, a phenomenon that was virtually the opposite with african us displaying a more humanlike, or advanced, head and yet retaining very primitive body proportions until quite a late stage in the overall hominid evolutionary picture. (142)

The "linear model" (above) of the evolution of the hominids based on the long arms-short legs theory illustrates the shift in body proportions from short legs (primitive) to long legs (derived) to short legs (primitive) to long legs once again. This model is supported by Henry Mcllenry; the author believes that it is more likely that there was a division early in hominid evolution that led to two separate experiments. The skeletons (above) from left to right: a male chimpanzee, a male afarensis, a male africanus, a male human. (142)

If I was to rely on logic - and there's not necessarily any comfort in logic from such a distant perspective of our past - I would have to accept that hominids in the two regions evolved entirely separately from each other. In turn that would mean that humanlike bipedalism, in the form of humanlike body proportions, had arisen twice in Africa ­ that there were two entirely different models for how we first started walking on two legs. If so, where does the ancient lineage of Homo lie? East or South? I didn't see how both processes could have led to the same genus. I remain convinced that it is extremely unlikely that a pre-afarensis creature like anamensis with a primitive hominid cranial morphology, but seemingly derived body, gave rise to a form like afarensis with a largely humanlike body that then evolved into the more primitive body of africanus again. This reversal does not make sense given the present fossil record. Something in this chain has to give, and it strikes me as the simplest hypothesis that africanus and afarensis must be sister species evolving from an as yet to be identified common ancestor.(142)

A male A. afarensis (left) walks beside a male A. africanus (right) in a 1997 physical reconstruction based upon the long arms-short legs theory. (142)

We should be...a little more circumspect when we talk of the robust australopithecines as being a bunch of evolutionary losers. Their species enjoyed a 1.6-million-year tenure on Earth before their ecological niche closed over, whether it was through competition with emerging Homo or an environment that shifted beyond their ability to adapt to it. That is nearly a million and a half years longer than our species has been around. The robusts are nevertheless an evolutionary enigma. Possessing massive teeth and jaws, and with the males sporting an imposing crest running down the center of their skull, their appearance must have been startling. There are three known species, and they have one major feature in common - huge teeth behind the canines. Their molars are gigantic, with some individual teeth nearly the size of a U.S. nickel. They also all tend to have multiple roots in the premolars so the enormous teeth can be held in the jaw, whereas modern humans generally have a single root. Their jaws were massive in order to create the support structure for their large grinding platforms. In stark contrast to their huge back teeth, their front teeth are surprisingly small. Their dental apparatus was modified for a nibble-and-chew lifestyle, which required enormous teeth to process this rough food and well­developed chewing muscles with large attachments along the side of the skull. Consequently, they had to have a massive skull to hold all this together, yet their cranial capacity would have been about one-third that of modern humans. (142)

Although I have argued the case for a southern African origin of humans, I believe that the underlying message that arises from a dispassionate view of the present evidence is that we are not in a position to identify a single region of Africa as the birthplace of humankind, particularly in the early hominid record. If anything, the evidence at hand suggests many evolutionary experiments were conducted during the course of the last four or five million years of human evolution across the continent. (142)

Southwest Asia

 

Egypt

 

Indus Valley

 

China

 

Europe

 Osmond Fisher, a fellow the Geological Society, discovered an interesting feature in the landscape of Dorsetshire--the elephant trench at Dewlish. Fisher said in The Geological Magazine (1912): "This trench was excavated in chalk and was 12 feet deep, and of such a width that a man could just pass along it. It is not on the line of any natural fracture, and the beds of flint on each side correspond. The bottom was of undisturbed chalk, and one end, like the sides, was vertical. At the other end it opened diagonally on to the steep side of a valley. It has yielded substantial remains of Elephas meridionalis, but no other fossils...This trench, in my opinion, was excavated by man in the later Pliocene age as a pitfall to catch elephants." Elephas meridionalis, or "southern elephant," was in existence in Europe from 1.2 to 3.5 million years ago. Thus, while the bones found in the trench at Dewlish could conceivably be Early Pleistocene in age, they might also date to the Late Pliocene. (138)

In 1855, a human jaw was discovered at Foxhall, England, by workers digging a quarry. John Taylor, the town druggist, purchased the Foxhall jaw from a workman who wanted a glass of beer...He noted that the bed from which the jaw was said to have been taken was 16 feet below the surface. The condition of the jaw, thoroughly infiltrated with iron oxide, was consistent with incorporation in this bed. Collyer said that the Foxhall jaw was "the oldest relic of the human animal in existence." The 16-foot level at Foxhall is the same which Moir later recovered stone tools and signs of fire. Anything found at level would be at least 2.5 million years old. (138)

Modern geologists place the blue clays at Castenedolo in the Astian stage of the middle Pliocene, which would give the discoveries from Castenedolo an age of about 3-4 million years. 1883, Professor Giuseppe Sergi, an anatomist from the University of Rome visited Ragazzoni and personally examined the human remains at the Technical Institute of Brescia. After studying the bones, he determined they represented four individuals--an adult male, an adult female, and two children. Sergi also visited the site at Castenedolo. He wrote: "I went there accompanied by Ragazzoni, on the 14th of April. The trench that had been excavated in 1880 was still there, and the strata were clearly visible in their geological succession." Sergi was convinced that the Castenedolo skeletons were the remains of humans who lived during the Pliocene period of the Tertiary. The case of Castenedolo demonstrates the shortcomings of the methodology employed by paleoanthropologists. The initial attribution of a Pliocene age to the discoveries of 1860 and 1880 appears justified. The finds were made by a trained geologist, G. Ragazzoni, who carefully observed the stratigraphy at the site. He especially searched for signs of intrusive burial and observed none. Ragazzoni duly reported his findings to his fellow scientists in scientific journals. But because the remains were modern in morphology they came under intense negative scrutiny. As Macalister put it, there had to be something wrong. (138)

In the 1850s, while constructing a church, workmen discovered an anatomically modern human skeleton at the bottom of a trench 3 meters (10 feet) deep. The layer containing the skeleton was 3-4 million years old. Arthur Issel communicated details of the Savona find to the member the International Congress of Prehistoric Anthropology and Archeology at Paris in 1867. He declared that the Savona human "was contemporary with the strata in which he was found." Deo Gratias, a student of paleontology, noted: "The body was discovered in an outstretched position, with the arms extending forward, the head slightly bent forward and down, the body very much elevated relative to the legs, like a man in the water." (138)

South America

 

Mesoamerica

 

North America

 

Other