Paralleling
the biological evolution of early humans was
the development of cultural technologies that allowed them to
become increasingly successful at acquiring food and surviving
predators. The evidence for this evolution in culture can be seen
especially in three innovations:
| 1. | the creation and use of tools |
| 2. | new subsistence patterns |
| 3. | the occupation of new environmental zones |
Tool Making
Some chimpanzee communities are known to use stone and wood as hammers to crack nuts and as crude ineffective weapons in hunting small animals, including monkeys. However, they rarely shape their tools in a systematic way to increase efficiency. The most sophisticated chimpanzee tools are small, slender tree branches from which they strip off the leaves. These twigs are then used as probes for some of their favorite foods--termites and ants. More rarely, chimpanzees have been observed using sticks as short thrusting spears to hunt gallagos in holes and crevices in trees where they sleep during the day time. It is likely that the australopithecines were at least this sophisticated in their simple tool use.
The
first unquestionable stone tools were evidently made and used by
early transitional humans and possibly Australopithecus
garhi in East Africa about 2.5-2.4 million years ago. While the earliest
sites with these tools are from the Gona River Region of Ethiopia, simple
tools of this kind were
first discovered by Mary and Louis Leakey associated with Homo habilis at Olduvai Gorge in
Tanzania.
Hence, they were named Oldowan
tools after that location. These early toolmakers
were selective in choosing particular rock materials for their
artifacts. They usually chose hard water-worn creek cobbles
made out of volcanic rock.
There were two main categories of tools in the Oldowan tradition. There were stone cobbles with several flakes knocked off usually at one end by heavy glancing percussion blows from another rock used as a hammer. This produced a jagged, chopping or cleaver-like implement that fit easily in the hand. These core tools most likely functioned as multipurpose hammering, chopping, and digging implements. Probably the most important tools were sharp-edged stone flakes produced in the process of making the core tools. These simple flake tools were used without further modification as knives. They would have been essential for butchering large animals, because human teeth and fingers are totally inadequate for penetrating thick skins and removing pieces of meat. Some paleoanthropologists have suggested that the core tools were, in fact, only sources for the flake tools and that the cores had little other use.
 |
| Oldowan tradition core tool (chopper) |
In
addition to stone tools,
Homo habilis probably made simple implements out of wood and other
highly perishable materials that have not survived. In the 1940's,
Raymond Dart suggested that australopithecines and early humans also used the
hard body parts of animals as clubs, daggers, and
other sorts of weapons. Dart proposed an
entire tool making tradition which he named
osteodontokeratic
,
based on the presumed use of bones (osteo), teeth
(donto), and horns (keratic). This idea has been rejected
by most paleoanthropologists today since there is a lack of
evidence for the systematic, shaping or even use of these materials
for weapons or other types of tools at this early time.
In addition, it
is unlikely that the earliest humans were aggressive hunters. They most
likely were primarily vegetarians who occasionally ate meat that was mostly
scavenged from the leftovers of kills abandoned by lions, leopards, and other large predators.
At times, they also may have hunted monkeys and other small game much as
chimpanzees do today.
Homo
habilis made and used
stone tools in the Oldowan tradition for nearly a
million years but with gradual improvements over time.
The early Homo erectus also used what could be described as advanced
or evolved Oldowan tool making techniques. By 1.7-1.6
million years ago, the skills of some Homo erectus
had
increased to the point that they were making more sophisticated
stone implements with
sharper and straighter edges. Their tool kits were sufficiently advanced
by 1.5 million years ago
to consider them to be a new tool making tradition now referred to as
Acheulian
.
It was named after the Saint Acheul
site in southwest France where these
kinds of tools had been discovered in the 19th century. However, the
Acheulian tool making tradition was
first developed in East Africa. Perhaps, the
most important of the Acheulian tools were
hand axes. They
are rock
cores or very large
flakes that have been systematically worked by
percussion flaking to an
elongated oval shape with one pointed end and sharp edges on the sides.
Since they were shaped on both faces, they are also referred to as
biface
tools.
In profile, hand axes usually had a teardrop or broad leaf shape.
Referring to these artifacts as hand axes may be misleading since we do not
know for sure whether they were primarily axes in a modern sense or even if
they were held in the hand. Based on tool edge wear
patterns and the brittle fracturing lithic materials that were used to make them,
it is likely that hand
axes were multipurpose implements used
for light chopping of wood, digging up roots and bulbs,
butchering animals, and cracking nuts and small bones. In a sense, they were the Swiss Army knives of their
times.
|
|
|
Acheulian biface tools (hand axes) |
Some of the Acheulian tools were shaped by additional percussion flaking to relatively standardized forms. For instance, the surfaces of late Acheulian hand axes often had many relatively small flake scars, suggesting that these tools were not completely made with heavy hammerstones. Late Homo erectus or their immediate successors must have begun using softer hammers for greater control in the final shaping process. Pieces of hard wood, antler, or bone would have functioned well for this purpose.
 |
|
| Percussion Flaking Techniques: hard hammer (left) and soft hammer (right) | |
While hand axes were the most diagnostic of Acheulian tools, they usually make up only a small percentage of the artifacts found at Homo erectus sites. In fact, these early humans made a relatively wide variety of stone tools that were used for processing various plant and animal materials. Their tool kits included choppers, cleavers, and hammers as well as flakes used as knives and scrapers. It is quite likely that Homo erectus also made many implements out of more perishable materials such as wood, bark, and even grass, which can be easily twisted together to make string and rope.
The Acheulian tradition of tool making spread from Africa into Southwest Asia by 1.4 million years ago and reached southern Europe by at least 600,000 years ago. Until recently, the lack of hand axes at Zhoukoudian and other East Asian Homo erectus sites suggested that the Acheulian tradition did not reach that far. It was thought likely that the same functions that hand axes performed in the west were being performed in the far East by other kinds of tools, perhaps made of bamboo. However, 24 sites in southern China have now been found to contain Acheulian tools dating back about 800,000 years. There remains controversy as to whether they include true hand axes.
Throughout most of the Homo erectus geographic range, there is clear evidence of progressive improvement in tool making over time. The late Homo erectus had more complex mental templates guiding them in the manufacture of their artifacts. In addition, the reliance on tools increased as the implements became more useful. By 400,000 years ago, major Homo erectus sites commonly had tens of thousands of discarded stone tools.
New
Subsistence Patterns
Anthropologists use the term subsistence pattern, or subsistence base, to refer to sources of food and the way it is obtained. A clear measure of success in human evolution has been the progressive development of new food getting techniques and the inclusion of new food sources. These measures have made it possible for humanity to increase in numbers from a few thousand australopithecines in Africa 3 million years ago to perhaps hundreds of thousands of Homo erectus by ½ million years ago. This trend of expanding and diversifying subsistence patterns making it possible for population growth continues to the present. In fact, it accelerated dramatically two centuries ago and is largely responsible for our burgeoning world population of over 6.6 billion people today.
Based on the analysis of tooth wear patterns and food refuse evidence, it is likely that australopithecines and early transitional humans were primarily wild plant food collectors and occasional scavengers of meat and eggs. By the time of Homo erectus, small game hunting and large animal carcass scavenging were apparently becoming much more common. The evidence of this change in subsistence pattern can be seen especially at late Homo erectus sites such as Zhoukoudian. Literally tens of thousands of fragmentary food refuse bones were found there. They came from pigs, sheep, rhinoceros, buffalo, and especially deer. In addition, there were large numbers of bones from small animals including birds, turtles, rabbits, rodents, and fish as well as the shells of oysters, limpets, and mussels. Some of these bones ended up in the cave at Zhoukoudian as a result of large carnivorous animals rather than humans, but there is sufficient evidence to suggest that by 1/2 million years ago, some Homo erectus were exploiting virtually every animal in their environment for food. They undoubtedly were harvesting vast amounts of wild plant foods as well. It would be a mistake to assume that Homo erectus had become an efficient specialized big game hunter. That development did not occur until more advanced Homo sapiens had evolved, several hundred thousand years later.
Occupation
of New Environmental Zones
Homo erectus was the first species in our line of evolution to expand their range beyond tropical and subtropical environments into temperate climatic zones of the Old World where they encountered relatively cold winters. This evidently occurred by at least ½ million years ago in Asia and a possibly few hundred thousand years earlier in Europe. It was made possible mainly by the success of new inventions and new subsistence strategies. The most important change may have been increased meat consumption as a result of hunting and more successful scavenging. The greatest difficulty living in temperate areas was probably not the cold weather but obtaining something to eat during the winter when fresh plant foods are scarce. It is in that season that meat would have been the most important calorie source.
The ability to use fire for
cooking and heating may also have been significant in the
successful colonization of colder regions. However, the first
convincing evidence of regular fire use for these purposes does not come until 400,000-300,000
years ago, when Homo erectus were evolving into
Homo heidelbergensis
(archaic Homo sapiens).
The earliest suggestive evidence of fire being associated with humans
was found at two sites in Kenya dating to 1.5
million years ago. In both cases, soil sediments appear to have been
exposed to high temperatures. However, it is not necessary to assume that
early humans were responsible. The burned soil could have resulted
naturally from lightning started wild fires that are common in the
grasslands of East Africa even today. Similar
questionable evidence has been found in South Africa dating to about
1,000,000 years ago. There is no
convincing evidence of human control of fire
at this early time. A 790,000 year old site in
Israel has more credible evidence, though there does not seem to have been
any cooking or repeated fire creation. The first reasonably good
evidence of cooking is in the form of burned bones and fire altered stones at the Chinese site of
Zhoukoudian dating
sometime between 550,000 and 450,000 years ago. All of these
sites in Africa and Asia with uncertain fire use indications presumably
would have been occupied by Homo erectus.
We have no evidence as to how Homo erectus might
have obtained fire or even if they had the ability to create it at will.
Implications
The cultural developments of Homo erectus essentially began a new phase of our evolution--one in which natural selection was altered by cultural inventions. This has been referred to as biocultural evolution. Culture can affect the direction of human evolution by creating non-biological solutions to environmental challenges. This potentially reduces the need to evolve genetic responses to the challenges. Normally, when animals move into new environmental zones, natural selection, operating on random mutations, causes evolution. In other words, the population's gene pool is altered as a result of adapting to a new environment. When late Homo erectus moved into temperate environments, nature should have selected for biological adaptations that were more suited to cooler climates. Such things as increased amounts of insulating body fat and insulating hair covering most of the body would be expected. Homo erectus evidently achieved much of the same adaptation by occupying caves, using fires, and becoming more capable at obtaining meat. By using their intelligence and accumulated knowledge, they remained essentially tropical animals despite the fact that they were no longer living only in the tropics. However, natural selection continued to select for increased brain size and presumably intelligence. This pattern of culture altering natural selection accelerated dramatically with the evolution of modern humans. Today, most of us live in cities and towns that are essentially unnatural environments and the rate of culture change has accelerated dramatically. We have occupied most environmental zones on land, and yet we are still essentially tropical animals physically. As a result, we perish rapidly if our cultural technology is taken away from us in environments in which the temperature drops to freezing.
NEWS: In the September 27, 2001 issue of the journal Nature, Rixiang X. Zhu of the Chinese Academy of Sciences in Beijing announced that stone tools made by Homo erectus about 1.36 million years ago have been found in the Nihewan Basin of northeastern China. This is the earliest confirmed evidence of Homo erectus in temperate regions of East Asia. These artifacts imply that Homo erectus were able to adapt to relatively cold winter climates more than a half a million years earlier than previously believed. Until the discovery of additional well dated sites confirming this evidence, it would be wise to hold judgment.