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Evolution                  2 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. 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)

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)

To explain the relatively slow rate of technological change between 2 million and 100,000 years ago, we must reflect on the fact that not only were our ancestors of this era less intelligent, there were also many fewer of them. Although technolgical innovation is not a simple product of the number of minds available to create new ideas, a strong relationship exists between population numbers and innovation in the simple hunting-gathering economies of the early and middle Pliestocene. Even as late as 500,000 years ago, there were probably only a million people in the entire worlde. Also, people of this era tended to live much shorter lives. Few survived past thirty years of age, and people learn a great deal and retain considerable creativity past thirty.(24)

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)

With only one human species surviving today but two or three a few million years ago, it's clear that one or two species must have become extinct. Who was our ancestor, which species ended up instead as a discard in the trash heap of evolution, and when did this shakedown occur? The winner was the light-skulled Homo habilis, who went on to increase in brain size and body size. By around 1,700,000 years ago the differences were sufficient for anthropologists to give our lineage a new name, Homo erectus, meaning "the man that walks upright." (Homo erectus fossils were discovered before all the earlier fossils I've been discussing, so anthropologists didn't realize that Homo erectus wasn't the first protohuman to walk upright). The robust man-ape disappeared somewhat after 1,200,000 years ago, and the "Third Man" (if he ever existed) must have disappeared by then also. As for why Homo erectus survived and the robust man-ape didn't, we can only speculate. (114)

Whether the first sojourner was Homo habilis at 1.9 million years ago or Homo ergaster at 1.7 million to 1.0 million years ago is less important than the elementary fact that two of these creatures did leave Africa and did occupy areas of far greater topographic and environmental diversity than anything "back home." That they were able to do so speaks volumes not only to their increasing capacity to use culture - inventions of various kinds - to buffer the variability inherent in new environments, but also to the continuing interplay between cultural behavior and continued increases in brain size and cognitive capacity. (130)

The fossil record shows no evidence so far of hominids living outside of Africa more than two million years ago, while even claims prior to a million years are hotly contested or scientifically disputed. On the other hand, remains of hominids older than two million years have consistently been found in Africa. The genetic evidence corroborates this, with most molecular biologists convinced that humans arose in Africa. (142)

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)

...shortly after this apparent period of diversification in the hominid line around 1.7 million years ago, a single species, Homo erectus, emerges as the first hominid, which almost any scientist would agree is definitely a direct human ancestor. (142)

Some time between 1.8 and 1.3 million years ago, Homo erectus succeeds in spreading out of Africa and occupying much of the Old World. Around 1.1 million years ago, we see the extinction of the robust lineage's in both eastern and southern Africa corresponding - perhaps not coincidentally - with the evidence of the first controlled use of fire at Swartkrans in South Africa. And by one million years ago, populations of Homo erectus are in the Far East, Asia, and Europe, and of course widespread in Africa. But for the next million years, while we have a good fossil record of human evolution in the Near East and Europe, and a fossil record of Homo erectus in the Far East and Indo-Pacific, the fossil record in Africa is almost nonexistent. While stone tools litter the landscape of Africa, indicating plentiful populations of hominids, we have only a tiny handful of fossils from across the continent. The record is so poor that we have begun to call this period in Africa the Million Year Gap. (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

We can see traces of our origins in all of the earth's ancient life forms, from the earliest marine creatures through the tree-shrews that lived tens of millions of years ago to our last primate ancestors--but only in the crucial interval of two to one million years ago did our genus, Homo, become become the dominanat primate in the world.(9)

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)

Two hominid fossils discovered in Kenya are challenging a long-held view of human evolution. The broken upper jaw-bone and intact skull from humanlike creatures, or hominids, are described in Nature. Previously, the hominid Homo habilis was thought to have evolved into the more advanced Homo erectus , which evolved into us. Now, habilis and erectus are thought to be sister species that overlapped in time. The new fossil evidence reveals an overlap of about 500,000 years during which Homo habilis and Homo erectus must have co-existed in the Turkana basin area, the region of East Africa where the fossils were unearthed.

"Their co-existence makes it unlikely that Homo erectus evolved from Homo habilis," said co-author Professor Meave Leakey, palaeontologist and co-director of the Koobi Fora Research Project. The jaw bone was attributed to Homo habilis because of its distinctive primitive dental characteristics, and was dated to around 1.44 million years ago. It is the youngest specimen of this species ever found.

The skull, discovered by Frederick Manthi of the National Museums of Kenya, was assigned to the species Homo erectus despite being a similar size to that of a habilis skull. Most other erectus skulls found have been considerably larger. But it displayed typical features of erectus such as a gentle ridge called a "keel" running over the top of the jaw joint. Analysis showed the skull to be about 1.55 million years old. The new dates indicate that the two species must have lived side by side. Professor Spoor explained, "the easiest way to interpret these fossils is that there was an ancestral species that gave rise to both of them somewhere between two and three million years ago."

Not so similar The fossil record indicates that modern humans ( Homo sapiens ) evolved from Homo erectus . However, to some researchers, the small size of the erectus skull suggests that species may not have been as similar to us as we once thought. On average, modern humans display a low level of "sexual dimorphism", meaning that males and females do not differ physically as much as they do in other animals. The scientists compared the small skull to a much larger erectus cranium found previously in Tanzania. If the size difference between the two is indicative of the larger one being from a male and the smaller being from a female, it suggests that erectus displayed a high level of sexual dimorphism - similar to that of modern gorillas. (34)

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; Our genus, Homo, is 2 million years old. (119)

By about 1.8 million to 1.7 million years ago, at the last glimmer of the Pliocene and the dawn of the Pleistocene, a new version of us appeared in east Africa - not coincidentally, with a better tool kit. Named Homo ergaster and equipped with a substantially larger body (the males may have reached six feet in height) and a proportionately bigger brain than its predecessor's, this species not only was fully adapted to terrestrial life but could also cope with climatic extremes its predecessors could not survive. Homo ergaster appeared in an Africa where the temperature and precipitation regime was changing from coolish and moister to very warm and very dry. They had attained the same body size as essentially modern humans, had lost the hairy body covering of their predecessors, and were probably the first of our remote ancestors to be able to cope with genuinely arid environments. Indeed, with a few minor differences, Homo ergaster is anatomically modern - but only from the neck down. (130)

The fossil record shows no evidence so far of hominids living outside of Africa more than two million years ago, while even claims prior to a million years are hotly contested or scientifically disputed. On the other hand, remains of hominids older than two million years have consistently been found in Africa. The genetic evidence corroborates this, with most molecular biologists convinced that humans arose in Africa. (142)

The flurry of early Homo species played itself out by about 1.8 million years ago. In East Africa there is still evidence of habilis and rudolphensis, but they seem to disappear within the next 100,000 years or so; and in what appears to be a startling evolutionary leap, we get the appearance of ergaster ("working man") at 1.75 million years ago. The best known example of ergaster, which really is an early form of African erectus, is the Turkana Boy discovered in 1984 by Richard Leakey and Alan Walker at Nariokatome on the banks of Lake Turkana. This strapping 12-year­old youth, who was 5 feet 3 inches tall at the time of his death, would have been well over 6 feet tall had he lived to be an adult. His athletic physique is proof that the preconception that humans have grown progressively taller over the millennia is wrong. In fact erectus would probably have been physically more powerful than any modern human being, with a body crafted to cope with the harsh conditions of the African savanna. (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. 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)

Lasting from l.78 million years ago to 0.4 million years ago, Homo erectus is one of the longest-lived hominid species. If evolution is thought of as a gradual, steady process, then we might expect erectus, if it was the direct ancestor of humanity, to exhibit such steady evolution toward the anatomically modern condition over its lengthy existence on the planet. ...all of the Homo erectus specimens, from the very oldest to the most recent, are "built on a common plan". Even brain size within the species can be shown to be fundamentally stable through time: There is no significant increase in cranial capacity within erectus from its earliest appearance in Africa l. 78 million years ago until it is replaced by Homo sapiens sometime after 400,000 years ago. Interestingly, this period of relative stability in brain size is also a period of great cultural stability regarding stone tools. The hand axes made by Homo erectus change only slightly from 1.4 million to 400,000 years ago. At about 400,000 years ago, however, a steep increase in brain size over a short interval is seen. This jump in brain size, in fact, is how the earliest appearance of members of our species is identified. Those changes produced and defined the first Homo sapiens in what is seen here as being a punctuational event. (170)

Southwest Asia

 

Egypt

 

Indus Valley

 Finds from Pakistan, China, Java and elsewhere raise the possibility that hominids were distributed across the warmer regions of the world by at least 1.5 million years ago. The lowered seas of the Pleistocene would have facilited this, opening rich coastal niches far out into the Southeast Asian archipelagos.(8)

Eolithlike implements that do not fit into standard ideas of human evolution continue to be found in parts of the world outside the Americas. Some fairly recent finds by British archeologists in Pakistan provide an example. These crude chopping tools are about 2 million years old. But according to the dominant African homeland idea, the human ancestor of that time period, Homo habilis, should have been confined to Africa. (128)

Many other discoveries of stone implements around 2 million years old have been made at other Asian sites, in Siberia and northwestern India. In 1961, hundreds of crude pebble tools were found near Gorno-Altaisk, on the Ulalinka river in Siberia. According to a 1984 report by Russian scientists A. P. Okladinov and L. A. Ragozin, the tools were found in layers 1.5-2.5 million years old. Another Russian scientist, Yuri Mochanov, discovered stone tools resembling the European eoliths at a site overlooking the Lena River at Diring Yurlakh, Siberia. The formations from which these implements were recovered were dated by potassium-argon and magnetic methods to 1.8 million years before the present. Recent evidence from India also takes us back about 2 million years. Many discoveries of stone tools have been made in the Siwalik Hills region of northwestern India. In 1981, Anek Ram Sankhyan, of the Anthropological Survey of India, found a stone tool near Haritalyangar village, in the late Pliocene Tatrot Formation, which is over 2 million years old. Other tools were recovered from the same formation. (128)

China

 Finds from Pakistan, China, Java and elsewhere raise the possibility that hominids were distributed across the warmer regions of the world by at least 1.5 million years ago. The lowered seas of the Pleistocene would have facilited this, opening rich coastal niches far out into the Southeast Asian archipelagos.(8)

Europe

 A team of scientists working in Georgia has unearthed the remains of four human-like creatures dating to 1.8 million years ago. In the journal Nature, the researchers outline details of the partial skeletons uncovered in a Medieval town. The bones reveal a mixture of primitive and advanced features, team leader David Lordkipanidze explained.

These early hominids may have been among the first to leave Africa to colonise the rest of the world."They are the earliest, undisputable hominids outside of Africa," Dr Lordkipanidze said."We are dating them between 1.7 and 1.8 million years old. They are the most complete collection of a Homo [species] from any site older than 300,000 years old," he told the BBC's Science In Action programme.

In many respects, the well-preserved fossils resemble Homo erectus, a species from the genus Homo that first appeared in Africa some two million years ago and quickly spread throughout Europe and much of Asia. They have remarkably human-like spines and lower limbs that would have been well suited for long distance travel. Their feet had well-developed arches. An apparently small difference in the size of males and females also puts them in the same company as Homo erectus and Homo sapiens. However, they also have relatively small brains and primitive upper limbs, traits which they share with the earlier Homo habilis, and even with the more primitive Australopithecus, which first appeared in Africa some four million years ago.

"They are smaller than what we thought Homo erectus could be," David Lordkipanidze explained."They have smaller brains; and also their body proportions, they are not completely human-like."In the [Nature report], we showed that their legs were very human but their hands were still ape-like. So, I would say these are quite mosaic features; this does not fit precisely the definition of Homo erectus before the Dmanisi finds. Maybe we are adding something new to the Homo erectus definition." (35)

The fossils of early humans have been found in Africa, Europe, and Asia (including China and Java), demonstrating they were not limited to one habitat. This array of fossils includes an interesting 1.7 to 1.8-million-year-old site in the republic of Georgia, between the Black and Caspian seas. The bones of six individuals have habilis characteristics, proving a type formerly assumed to have been limited to Africa was actually more widespread. Members of this general erectus group overlapped with Homo sapiens for what could have been several hundred thousand years. Such overlaps suggest that one did not directly evolve into the other by a process of natural selection. (113)

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)

South America

 

Mesoamerica

 

North America

 

Other