F-2. HOMO HABILIS AND HOMO ERECTUS:
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Homo habilis 2.3 to 1.44 mya

"In the earliest times , men lived in the dark and had no animals to hunt. They were poor, ignorant people, far inferior to those living nowadays. They travelled about in search of food, they lived on journeys as we do now, but in a very different way. When they halted and camped, they worked at the soil with picks of a kind we no longer know. They got their food from the earth. They lived on the soil. They knew nothing of all the game we now have, and therefore had no need to be ever on guard against all those perils that arise from the fact that we, hunting animals as we do, live by slaying their souls. Therefore they had no shamans, but they knew sickness, and it was fear of sickness and suffering that led to the coming of the first shamans" (Eskimo/Iglulik: Aua) (Halifax, 1979).

A. afarensis
Australopithecus  afarensis

A. africanus
A. africanus
H. habilis
Homo habilis
(Source: Larry Williams sculptures, http://www.landofskulls.com/)

A. africanus cranium (left) vs. H. habilis

A hint to our history is found in verbal traditions and practises of recent hunter gatherers. Tasmanian Aborigines came from the mainland of Australia at least 10,000 years ago. They used spears and stone tools like those used on the mainland, but did not use spearthrowers, boomerangs, shields, axes or adzes. This may suggest that these tools evolved after their separation from the mainland. The above quote from an Eskimo mentions digging sticks. Aboriginal women used a hard pointed digging stick for all their collecting, be it to dig up roots or small animals such as lizards or snakes. Men did not use these.

Our dentition is that of a vegetarian. Our earliest ancestors may have relied heavily on root foods such as yams. Yams refer to a group of tuber bearing plants that includes about 600 species. They grow in moist hot climates and are today a major food crop in tropical countries. The starch tuber grows underground and would have to be dug up. A group of people, called the Banda have left remains of tools, identified as hoes or picks and dated as up to 75,000 years old. They lived in the region between the Zambezi and Limpopo rivers. Such wild plants would have represented an unexploited resource before early humans found that some of them were edible (and others toxic).


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Habitat

Savannah woodlands replaced tropical forests between 2.5 and 2.7 million years ago (or 3.3 to 2.4 mya) during an ice age that caused an 11 degree drop in global temperatures. The Pleistocene (0.045-1.8 million years ago) (Sci. Am. 1994, Oct.), a period of climatic change marked by cold spells, repeated glaciation and the shrinking of tropical forests, followed. Australopithecines share a common ancestor with the lineage that evolved to become H. habilis . This ancestor to the Hominidiae branched in two directions. One branch, led to the robust australopithecenes and the other to H. habilis . A. afarensis , which became extinct about 2.9 million years ago, is believed to be the direct ancestor of H. habilis (Avers, 1993). A. africanus became extinct about the time of the appearance of H. habilis , not allowing enough time for the evolution of the one into the other. So close are the two, that some scientists thought the two were the same species (Parker, 1992). Paranthropus robustus and P. boisei ( Zinjanthropus boisei (Leakey, 1959)) existed when the first hominine , Homo habilis lived in East Africa 1.44 to 2 million years ago (Nature, 2007) (1.9 to 1.6 Mya by other estimates (Lemonick & Dorfman, 1999) and 2.3 to 1.6 million years ago ( PBS.org )). Australopithecines coexisted (Johansen and Taieb, 1976) with the first hominines (genus Homo ) for up to two million years so there must have been distinct separations of their ecological niches during this time (Coppens, 1994). All Australopithecines were extinct by less than one million years ago.

KNM-ER42700 Homo habilis , a maker and user of crude stone tools, appeared up to 2.3 million years ago. Giant buffalo and other grazer animals replaced forest antelope fossils while H. habilis appeared. This suggested that grasslands had expanded and tree cover was less. It had small teeth, signs of a protruding nose, was lightly built, at 1.52 m tall and weighing 45 kg, and had a brain volume of about 650 cc. Males were much larger than females, similar to the sexual dimorphism of the Australopithecines. Animal bones found with habline tools show scratch marks suggesting that these creatures ate meat and also fruit, insects and plants. Tools and a jaw bone fragment dated at 1.9 million years old have been found in central China. Other remains of this species at archaeological sites come from Tanzania ( Olduvai Gorge ), Kenya ( Koobi Fora ) and South Africa (Sterkfontein) show an early and wide distribution for Homo habilis (view of Homo habilis lower jaw) ©1 . A recent discovery (2001) of a 1.75 million year old human skull from the strata below the ruins of the medieval town of Dmanisi in southern Georgia may extend the range of a close relative of H. habilis . This skull and other bones show some features similar to Homo habilis . This is the smallest (600cc), most primitive hominid skull (see hominid books) ever discovered outside of Africa. It has large apelike canine teeth. Skulls that resemble  Homo ergaster and a jaw bone that falls well within the range of Homo erectus have also been found at this site. The finds have been classified as Homo egaster , a species more advanced than habilis but more primitive than erectus.

Slight morphological differences in larger fossils found at Koobi Fora, dated between 1.8 and 1.9 million years old, have led to the identification of another habline species, Homo rudolfensis with a brain volume of about 775 cc. There is a fossil mandible of this species up to 2.4 million years old (Johansen & Edgar, 1996). K. platyops has morphological similarities with Homo rudolfensis ( KNM ER 1470). Homo habilis is smaller-brained creature with an archaic postcranium, and Homo rudolfensis as larger-brained with a more modern postcranium.

h-georgicusHomo georgicus is another species, named in 2002, from fossils found in Dmanisi, Georgia, which seem intermediate between H. habilis and H. erectus. The African H. ergaster is also similar and may be ancestral to this species.The fossils are about 1.8 million years old, consisting of three partial skulls and three lower jaws. Brain volumes vary from 600 to 680 cc.  A partial skeleton was also discovered in 2001 so more details should emerge (Vekua et al. 2002, Gabunia et al. 2002). H. georgicus may be the first hominin species to settle in Europe, some 800,000 years before H. erectus.

Stone tools from the Omo valley in Africa are as old as 2.4 million years (Toth & Schick, 1993). At present there is no definite evidence of Australopithecine tool-making or use, so anthropologists usually attribute the oldest tools to H. habilis . Another species recently identified, the 2.5 million year old Australopithecus garhi , has been found in the vicinity of carefully manufactured stone tools. While no other fossils have been found within this vicinity and period, A. garhi remains as the possible link between Australopithecus afarensis and Homo species. Animal remains from this region and period have been found with signs of cut marks, chop marks and hammer marks, showing that this species ( A. garhi ) was a meat eater and skillful tool user (Lemonick & Dorfman, 1999), ( Aiello and Imber, 2001) . Some of the tools are of materials not from the locality, so they had to be carried by the user.

Living on the African landscape, H. habilis would have been prey to the smaller cats such as leopards and even the larger birds of prey, such as the African crowned eagle. Fossils of this species are found in levels from the base called Bed I to the middle of Bed II of the Olduvai Gorge, spanning a period of 750,000 years (at least 500,000 years)! Little physical change took place during this period, suggesting a successful and enduring species.

At a site in Ethiopia (Abyssinia), on the Omo River is a geological bed that has yielded a fascinating series of fossils. The Omo river lies on the eastern side of the Rift Valley. It traces a three million year period starting four million years ago. During this time there is clear evidence of the climate changing from humid to drier conditions . Vegetation evolved to suit drier climates. Pollen remains change from representing 24 taxa of trees to 11 over the 3 million year period, while the proportion of grass pollens increase (from 0.4 to 0.01 change in tree to grass pollen ratio). Various species identified from the older strata ( Celtis, Acalypha, Olea and Typha ) that grow in humid habitats, diminish and sometimes disappear from the record of recent strata, replaced by plants typical of dry climates. Associated with this change in vegetation is a change in the animals that frequented this habitat. Robust australopithecines ( P. aethiopicus , P. boisei ) evolved from the gracile ancestor ( A. afarensis ) during this time. All the animal evolution in this area is closely associated with the climatic changes.

At the oldest levels, representing four million years ago, are found forest dwelling animals such as the monkey ( Galago ), rodent species ( Mastomys , Grammomys , Paraxerus , Thryonomys , and Golunda ) and forest bats (Chiroptera: Eidolon and Taphozous ). Herbivore dentition, such as in elephants, rhinoceros, Hipparion (horse ancestor), hippopotamus, pigs and antelope evolve to become more complex to process more grassy and less leafy diets. Grasses wear down teeth more quickly and animals have to adapt to this. As the habitat opened to grassland, animals had to cover further distances and running became more important to escape predators. Grazer feet became more digitigrade, with specialised hoofs. Various regions in the world, including the strata of Omo, show that the whole earth cooled between 3.3 and 2.4 million years ago. Eastern Africa became progressively drier. Other archaeological sites do not span this period - Laetoli and Hadar are too old, Olduvai is too young and East Turkana had a stratigraphic gap at this point (Coppens, 1994). By one million years ago open grassland animals such as the true horse ( Equus ), antelopes ( Megalotragus , Beatragus and Parmularius ), and dry savannah species of hare ( Lepus ), bat ( Jaculus , Heterocephalus ), and rodents ( Aethomys , Thallomys , Coleura and Gerbillurus ) had evolved.

The main features of the transition from Australopithecines to H. habilis are the use of tools and an enlarged braincase (700cc) (Avers, 1989) (600 to 750 cc (Gore, 1997)). H. habilis could walk upright like modern humans, but could probably also climb trees to sleep, feed or escape predators. Their hand and foot had a combination of ancient and modern features, expected from an early ancestor. By the time that H. habilis arose, the foot still fell somewhere between that of a man and gorilla in its weight-bearing capabilities! Even the anklebone suggests their walking differed from the human striding gait. The robust lower legbones, the tibia and fibula showed that the adaptation to bipedalism was even less specialised at the knee joint. This bipedal, plantigrade primate thus had a different gait to modern humans, but not necessarily less efficient, and perhaps superior (see details on the australopithecine hip [2]). An adult female fossil representative of this species stood only 90 cm high, with hands hanging over the knees as in apes! These features of H. habilis are almost identical to those of A. afarensis , showing here that the primitive apelike characteristics served well in the niche of this creature in nature for a very long time.

Milton (1993), having found a trend among the primate species he had investigated, said, "the striking expansion of brain size in our genus shows that we became so successful because selection amplified a tendency inherent in the primate order since its inception: that of using brain power, or behaviour, to solve dietary problems. Coupled with anatomic changes - and with the associations (found) in living primates between larger brains and a high quality diet - this increase also points to the conclusion that the behavioural solution was to concentrate on high-quality foods." Leakey (1993) supports this, stating, "By broadening the diet to include meat, early Homo achieved both stability and rich nutrition. Meat represents high concentrations of calories, fat, and protein. This dietary shift in Homo drove the change in the pattern of tooth development and facial shape." Associated with this change was the use of tools. Also, carnivores require a large home range, so this dependency required a more mobile species (Time, No. 11, 1994).

Noting that Homo habilis made the tools deliberately and with design is important (Cardwell, 1994). Materials for the tools came from two nearby locations. They made some tools from larva only 2 kilometres from their site of discovery (beds I & II). Other materials were seldom found farther than 4 kilometres! In bed I are about six different tools. In bed II more than 10 different tools were found. As with the spider monkey's reliance was upon behaviour and high energy food resources , so the early hablines must have evolved a strong spatial and temporal sense before the adoption of tool use. A spider monkey may search out a specific fruit tree species in a particular locality and in a certain season. As an advance on this, a chimpanzee will go to one site to collect grass stems and thin twigs. He will then search out termite mounds, where they "fish" for termites by poking the grass stalks down the termite holes and drawing out termites attacking the stem in defence (Burenhult, 1994). This degree of foresight is further evolved in Homo habilis who established "caches" of stone for future use and shaped tools for a purpose. The gradations of mental computation for the knowledge of available food resources, to the taking of a simple tool to a food source and then the planned modification and storage of tools is small, but laid the path of technological evolution and brain enlargement that led to modern humanity.

Predation upon larger prey, left fewer fossil bones in higher levels. Sharp stone flakes were probably used to cut through hides. In the upper bed II, more giraffes, hippopotamus and rhinoceros are found. Hunting larger prey covers a period of 150,000 years. They made more recent tools from rock 8 and 10 kilometres (Bed III) away. With the fossils found closer to the surface and above the others, materials came from many sources, possibly through a network of supply routes from sources up to 20 kilometres away (Bed IV) (Reader, 1988).

While stone and perhaps wood were the only or major materials used for tools, the possible inventions would have been limited. There is a trend that the more resources a community uses, the more it will invent (Cardwell, 1994). Usually, a unique innovation leads to many related inventions not implied from the original breakthrough. We see such a trend in human technological evolution.

At Olduvai, evidence suggests that there may have been a division of labour between males and females, the males hunting for meat and the females collecting energy-rich plant foods. If this is so, it represents the same successful pattern of culture and behaviour that persisted into the twentieth century with some people such as the Australian Aborigine and African Bushman. Food shared by H. habilis from some type of central collection point would have enhanced cooperation and communication.

Homo habilis made tools from rocks suitable for the production of one tool or another and some tools required more time to make than others. There is even some evidence that apparently simpler tools made with different materials was an advance. A sharp, clean edge could be made in a minute through the removal of a single flake while other materials flaked differently and took 5 to 7 minutes to prepare for use. Actual use of stone age tools showed the advantage of using a heavy tool to effectively skin an animal such as a zebra. Also, it requires a person of a suitable size to yield the tool! Flakes from tools also served to disjoint a carcass, cut sinews or scrape the skin. The tool kit of a hunter could thus be simple and light, consisting of a "hammerstone" and some large tools. Such efficient simplicity would be necessary for a mobile hunter.

In summary, these creatures made tools in pursuit of an end, or as a solution to a need and showed the ability to identify a problem and solve it. Archaeologists identify two different tool cultures, one called Oldowan and persisting unchanged throughout Beds II, III and IV, and another that appeared suddenly in the middle of bed II and called Acheulean. The two are found in close proximity but remain culturally distinct. Acheulean culture belongs to H. erectus, which migrated into the area during a dry period, when the local lake receded and the fauna changed.The oldest Acheulean tools are dated at 1.76 million years old.

Homo erectus 1.8 to 0.3 million years ago

Fossil evidence hints at the progressive evolution of technological and social skills to ensure survival. Stone tool use during our history, progressed or changed slowly (Cardwell, 1994). At the Olduvai Gorge in Tanzania stone tools become increasingly sophisticated from the oldest, lowest level (level I: 1.9 million years old) through to the higher levels (1.2 million years old for bed II). These in turn require the evolution of skills to use the tools and eventually the technological culture that characterises humanity. Olduvai's earliest sites, known as DK., has the simplest tools with least variety but with a definite use or purpose in their formation. Crude choppers or hammer-stones of varying size were the simplest, fitting easily into the hand and with an edge formed by removing flakes from either side along one face. In Africa, a technological shift in tool design to handaxes, cleavers or picks occurred about 1.76 million years ago . Anthropologists call these Acheulean (Mode II) as opposed to the earlier Oldowan (Mode I) stone technology. This new technology then spread to the Middle East, Europe and parts of the Indian subcontinent (Toth & Schick, 1993). This more sophisticated Acheulean stone technology coincides roughly with the appearance and spread of H. erectus. Fossils and tools of this species have been discovered in Indonesia (dated at 1.8 millions years old) and Dmanisi, in the Republic of Georgia (dated at over 1.7 million years old) (Time V155 No.20). The Dmanisi site's fossils may represent H. ergaster rather than H. erectus .

A two-million-year-old skull endocast of H. habilis shows a sulcal pattern in the left frontal lobe. In humans this area is associated with Broca's speech area, so researchers believe that H. habilis had at least the beginnings of speech (Falk, 1993). Further studies of skull endocasts and stone flakes suggest that H. habilis tended to be right-handed and that the right hemisphere of the brain was involved with the visiospatial orientation of tool production. The "handedness" continues in H. erectus . Although the Oldowan tools were technologically simple, their production two million years ago required the ability to recognise acute angles on stone cores from which to make tools. Good hand-eye coordination, precision, dexterity and a "power-grip" were necessary to make these tools (Toth & Schick, 1993).

Social Structure

By two million years ago, the social structure of the ancestor of humanity already included the idea of a home base. They transported raw materials and many prey species over long distances. They carried some rocks more than ten kilometres from their geological source. It is not certain whether they got meat through hunting or scavenging, but tool cut marks are found on bones. From this social and organisational context the ancestors of humanity arose. Today we see that in the development of our own children, a child of three or four is too heavy for a mother or father to carry easily over long distances. However, the child is still too young to cover long distances by running on its own. Such a child's development gives us some hint to the social structure that shaped our early evolution. Our children's physical development is a very ancient feature of humanity. Humanities' ancestors could hunt using tools. This adaptation, shaped our development over millions of years. As Reader (1988) said, "In a very real sense our intellect, interests, emotions, and basic social life - all are evolutionary products of the success of the hunting adaptation."

Homo erectus arose in Africa about 1.6 to 1.8 (and maybe even 2 (Time No. 11, 1994)) million years ago. Fossil remains of H. erectus found in Bed II of the Olduvian Gorge are about 1.2 million years old. (view of Homo erectus lower jaw) (side view of Homo erectus lower jaw) (click to see side view of skull) (click to see front view of skull) ©1 . Existing in the time between Australopithecus afarensis (3.75 to 3 Mya.) and H. erectus were H. rudolfensis , H. habli s and Homo ergaster . Until recently H. ergaster (1.5 to 1.75 Mya.) was placed within the H. erectus group, but it is now placed as a transition species between the hablines and our human lineage (Groves, 1994) (Johansin & Edgar, 1996). Homo habilis is then not necessarily a direct ancestor of H. erectus  as the existence of each species overlaps for at least 200,000 years. Other fossil evidence shows that Homo habilis  and  H. erectus lived side-by-side about 1.5 million years ago in parts of Kenya for at least half a million years (Nature, Aug 07). Their co-existence makes it unlikely that Homo erectus evolved from Homo habilis. As separate coexisting species they must have had their own ecological niche, so avoiding direct competition. The teeth and jaws are larger in Homo habilis than Homo erectus, suggesting that habilis ate tougher food, such as vegetation.

Found in Eastern Africa, H. erectus has more modern arm and leg proportions, smaller jaws and a more projecting nose. Acheulean culture and the use of handaxes that appeared suddenly in the upper part of Bed II come from H. erectus or H. ergaster . During this period, the climate in East Africa was becoming drier and cooler, and the landscape less forested (Aiello and Imber, 2001).

During this period three hominid lineages existed, H. habilis , H. erectus and the australopithecines (see skulls of each species ) (see hominid books). A complete cranium of Homo ergaster and Australopithecus boisei have been removed from the same sediment layer, showing clearly that more than one species of hominid coexisted (Johanson & Edgar, 1996). Differences between these species are so slight that some researchers once insisted that there is not enough "morphological space" for H. habilis between Australopithecus and H. erectus , let alone for the addition of H. ergaster to the sequence. However, that these are distinct species is now widely accepted. A. boisei shows the morphology of a herbivore eating hard foods such as nuts, seeds and roots, while H. ergaster used heavy tools, suggesting a more carnivorous diet. Why did scientists not include H. habilis within the Australopithecines? As well as morphological differences, the use of stone tools and the larger brain volume favour the inclusion of this creature within the Homo genus. Also, as Australopithines are extinct and Homo survives, fossils with distinctly Homo features belong within the surviving lineage: Homo (see phylogeny ).

H. erectus was a successful and mobile species and it appears that tool-use enabled it to easily extend its range and occupy different habitats. It lived in groups (possibly up to 100), made tools such as handaxes and definitely made regular use of fire; characteristics requiring communication. Analysis of the tools of Homo erectus shows two technologically distinct regions. In Africa, western Europe, and Southwest Asia is the classic Acheulean hand axe tradition. Chopping tools are more common in East and Southeast Asia suggesting a different means of subsistence (Burenhult, 1994). Around 412,000 years ago, H. erectus was hunting rhinos, elephants and bison in Germany and using tools of stone, bone, wood and antler (Gore & Garrett, 1997).

Today fossils and finely fashioned multifaceted hand axes and cleavers are found widely distributed across the globe. Dispersal of H. erectus into Europe and Asia took place early in its history (Wilson, 1992). It probably left Africa to colonise other parts of the world at around 1.8 to 2 Mya, being the first nomads, following seasonal changes and game migrations. Homo erectus olduvaiensis (from Olduvai) is 1.2 million years old. Recent finds from the Soviet republic of Georgia may extend this date back to 1.8 million years. Fire enabled its dispersal into colder parts of the world. Life in cold climes would have also required wearing clothes, but there is no fossil evidence for this. Homo erectus used fire by 300,000 years ago, while ancient sites as old as 750,000 years in France and 1.4 million years in Kenya are more controversial (Parker, 1992), (Fletcher, 1994). Its widespread dispersal occurred much earlier. By 1.7 million years ago Homo erectus had spread to Koobi Fora in Kenya, Mojokerto in Java and Dmanisi in Georgia (Time, V155 No. 20). As a hunter of wild game, it spread where is prey was, no longer bound to specific habitats or vegetation.

Distribution:

Not all fossils are associated with stone tools, but other materials that decompose, such as bamboo can be more versatile than stone, and do not leave any fossil trace. Fossil remains of H. erectus in Java extend over a period from about 1 million until 100,000 years ago. In China their presence extends from 800,000 until 230,000 years ago (Groves, 1994). Stone tools from Italy (Europe) are about 730,000 years old (Burenhult, 1994). In Thailand (Southeast Asia) and Israel (Southwest Asia), fossils as old as 700,000 years have been found. Studies of these fossils show that there was an increase in brain volume over time. The smallest brain volume, at 600cc, is the 1.7 million year-old D2700 from Dmanisi, Georgia. Brain volumes from about 700,000 years ago are between 815 and 1059 cubic centimetres, while brain volumes of 100,000 years ago are between 1055 and 1300 cubic centimetres, close to the human range of 1040 to 1595 cubic centimetres. The more primitive Java lineage ( Homo erectus erectus ) appears to have evolved into the Chinese population,
( Homo erectus pekinensis ). pekinensis ©1

The skulls H. erectus show slight physical differences, but they are not necessarily different species. As such the Asian Homo erectus , African Homo ergaster and European H. heidelbergensis , may all be the same species. Specimens from Dmanisi, Georgia, has been classified as H. ergaster. It exhibits a thin browridge, short nose and large canine teeth. All three used the Acheulean tool industry (with the Dmanisi exception ), showing a cultural relationship supporting the morphological association (see below for more on lithics ). An Englishman's and Australian aborigine's skulls would show just as distinct differences. There are also racial differences between African and European fossils and those found in Java and China. Anthropologists group specimens from Germany, England and the French Pyrenees of 200,000 and 300,000 years and older as Homo (erectus) heidelbergensis . Similar fossils from Greece are between 300,000 and 400,000 years old (Burenhult, 1994). This lineage led to the Neanderthals that lived from 200 thousand to 35 thousand years ago (Andrews & Stringer, 1993).

Skeleton:

From the neck down the Homo erectus fossils appear like human skeletons and stood about 5 ft 6 in. tall, but the brain volume was still small (750 to 1300 cubic centimetres). A ridge along the top of the skull, the sagittal keel, is common in H. erectus , but it is not associated with muscles, as in A. robustus , but is simply a raised midline bony feature (Aiello & Dean, 1990). Humans, A. afarensis and A. africanus skulls do not have a sagittal crest. The larynx is found high in the throat, similar to that of a 2-year old human child, limiting the range of sounds that could be made. Their protolanguage could not therefore attain the complexity of human language.

The ridge in H. erectus may be a vestigial feature. It may have vanished in the evolution to H. sapiens or it may suggest that H. erectus was not the direct ancestor of H. sapiens . It is likely, as noted by the anthropologists Colin Groves and Bernard Wood, that H. erectus was not a direct ancestor of H. sapiens . Bilsborough, however, observes that "the accumulating numbers of morphologically intermediate specimens from all three Old World continents point to a continuity between late H. erectus and archaic H. sapiens . They also classified Homo heidelbergensis as the subspecies Homo erectus heidelbergensis or simply called "archaic Homo sapiens . "These fossils come from Europe and Africa and have relatively curved brow ridges that do not flare out sideways as do the specimens from China and Java. There is no midline and back thickening of the braincase and the ear region and mandibles differ. H. erectus erectus from Java has a primitive forehead shape and seems to have evolved into H. pekinensis in China. (Other morphological variations of H. erectus  have been named H. antecessor, H. cepranensis, H. ergaster, H. georgicus, H. mauritanicus and H. soloensis).

Female H. erectus are much smaller than the males, a feature in some species termed sexual dimorphism. Difference in size between males and females are often related to monogamy. Primates with same-sized males and females, such as gibbons, tend to be more monogamous. Species that are not monogamous, such as gorillas and baboons, have males much bigger than females. This suggests that Homo erectus reproduced with multiple partners.

Development of tool-use as an adaptation led to an interactive process, subject to natural selection , where greater skill in tool use would have been a survival advantage, and greater skills or dexterity would have required a larger brain. Brains require considerable energy to maintain their metabolism, so the evolution of a larger brain must have had a selective advantage. H. erectus braincases do get bigger over the years, increasing from 775 to 1300 cubic centimetres (Time, 11, 1994), (Burenhult, 1994). Fossils from China (at Zhoukoudiannear Beijing) showed an increase in brain volume ranging from 915 to 1140 cubic centimetres ("Peking man") and increased tool sophistication through time. Tool use, associated with hunting and meat eating, would have led the human ancestors upon the evolutionary path of increased brain volume! Advantages of cooperation in hunting, would have led to the social development that has accompanied our evolution, setting that early creature upon the road to humanity.

Acheulean Tools:

Homo erectus had a recognisable tool culture, called the Acheulean tool tradition, that changed little over an 800,000 year period. They term pebble-tools of the earlier Homo habilis Oldowan (click to see image of tools) ©1 . The 1.7 million year-old stone tools found with the hominid (see hominid books) ( Homo ergaster/erectus ) remains at Dmanisi are simple choppers and scrapers similar to the Oldowan tools found in the Olduvai Gorge, Tanzania (Gabunia et al, 2000). This implies that early humans with primitive technology were able to expand out of Africa. Also, to extend into such a cold climate would have required increased social interdependence and dependence upon meat as a food resource. Tool types increase and require more skill to produce and become more specialised with H. erectus (click to see image of Acheulean tools. These are hand axes used by H. erectus) ©1 . A handaxe that fits into the hand is the classic Acheulean tool, but they shaped these to serve as scrapers, side scrapers, backed knives, small choppers, picks, points and borers (Parker, 1992). The most ancient of these tools, from Africa, are 1.3 to 1.2 million years old, and although the design and quality improve through time, the same basic tools were still being used in Europe only 100,000 years ago. They replaced it in Africa between 200,000 and 150,000 years ago. From the fossil record it appears that the handaxe technology entered Europe 200,000 years after H. erectus (Toth & Schick, 1993). Acheulean handaxes were also used in west and southern Asia. It is not well represented in East and South East Asia, where a local chopping-tool industry dominated (Burenhult, 1994).

Our existence as social hunters and gatherers may have also contributed to the evolution of larger brain volumes. An interesting finding in "big cats" is that a relationship exists between brain size and the amount of sociality. Nonsocial pumas, jaguars and leopards have smaller brain sizes than lions (Brakefield, 1993). Social existence in lion prides in some way promotes larger brain sizes. This is an important comparison because of what it cannot include. The only similarity between the lion and humans is the existence of a social structure. We must exclude fruit eating, meat eating (because smaller brained cats also eat meat), tool use, bipedalism and the use of hands in this comparison as possible factors influencing brain size. It shows that more than one factor probably influenced the increase in brain size during human evolution.

Specific features characterise tool use by Homo erectus . These tools were more complex, requiring greater operational skills for their manufacture. An understanding of various geometric relations and symmetry was necessary. With the evolution of H. erectus , their tools became more standardised indicating improved communication and cognition between individuals. Changes in tool design were remarkably slow. This technology reached southwestern Asia by 1.2 million years ago and East Asia by 0.7 to 1 million years ago. Earlier migrants to Europe and parts of Asia did not use Acheulean technology (Early and Middle Pleistocene). Handaxes and cleavers are absent. This is possibly due to a lack of materials in newly occupied areas leading to a loss of technological transmission within one generation. It took several hundred thousand years for the bifacial tool forms to reach and spread through Europe and Western Asia. Acheulean technology had spread throughout Europe by 500,000 years ago. This technology was never used in Eastern Asia, where other materials, such as bamboo may have been more popular. Geographical barriers such as the Himalayas and tropical forests may have also prevented the spread of bifacial handaxes to this area. It thus seems that H. erectus did not have well enough developed communication skills, cognition and traditions to transmit information over a few generations. Similarly the slow evolution and long persistence of this technology show that it was very fixed, and probably dependent upon physical demonstration for its transmission. (Toth & Schick, 1993). This is not really surprising as it often happens with humans even today.

By 500,000 years ago brain volumes and dentition of Old World H. erectus populations had essentially attained modern proportions. This is only 2.5 lines into our hypothetical 460 page book of life! "The chronospecies H. sapiens , or the modern species derived from the archaic species by vertical evolution had arrived" (Wilson, 1992). The earliest Australian stone industries of 40,000 years ago, are similar to the Southeast Asian technology of the late Pleistocene! By 30,000 to 35,000 years ago, anatomically modern humans were also living in China, Borneo and Java (Toth & Schick, 1993). Access to Borneo and Sulawesi and Sumatra may have been via a land bridge during the Lower Pleistocene times (Bellwood, 1980). This whole area may have been a single land mass (Sundaland) 40,000 years ago. They also colonised Australia and New Guinea during this period. New Guinea and Australia may have formed a single land mass (Sahulland) 40,000 years ago.

Homo sapiens (click to see human skull) ©1 evolved after traversing the series from Australopithecines to H. habilis and then to H. erectus . Homo erectus heidelbergensis ( Homo heidelbergensis ) appears to provide the transition between more primitive Homo erectus and Neanderthals and modern humans. H. heidelbergensi had a larger brain volume (Arago XXI at 1,166cc (Johansen & Edgar, 1996)) than H. erectus . The evolution of neanderthals, from this ancestral species, occurred well before that of modern humans . Fossil remains suggesting a transition from H. heidelbergensis to humans have been found at Omo River in Ethiopia (130,000 years old), Ngaloba in Tanzania (130,000 years old), Jebel Irhoud in Morocco (120,000 years old) (Groves, 1994) and Eliye Springs. A group of about 23 individuals from Atapuerca in Spain, and other finds in England (Swanscombe) and Germany (Ehringsdorf), all dated at between 300 and 200 thousand years old show features intermediate between H. heidelbergensis and H. neanderthalensis .

GOTO to next chapter: Homo neanderthalensis Return to: Human evolution index page

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by Laurence Evans 1998 - 2008

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