The Olduvai GorgeEdit
2 million years ago, Olduvai Gorge (Tanzania) was a lake. Its shores were inhabited not only by numerous wild animals but also by groups of hominids, including Paranthropus boisei and Homo habilis, as well as the later Homo erectus.
The gorge, therefore, is a great source of Palaeolithic remains as well as a key site providing evidence of human evolutionary development. This is one of the main reasons that drew Louis and Mary Leakey back year after year at Olduvai Gorge.
Certain details of the lives of the creatures who lived at Olduvai have been reconstructed from the hundreds of thousands of bits of material that they left behind: various stones and bones. No one of these things, alone, would mean much, but when all are analyzed and fitted together, patterns begin to emerge.
Among the finds are assemblages of stone tools dated to between 2.2 Myrs and 620,000 years ago. These were found little disturbed from when they were left, together with the bones of now-extinct animals that provided food.
Mary Leakey found that there were two stoneworking traditions at Olduvai. One, the Acheulean industry, appears first in Bed II and lasts until Bed IV. The other, the Oldowan, is older and more primitive, and occurs throughout Bed I, as well as at other African sites in Ethiopia, Kenya and Tanzania.
Until about 2.5 million years ago, early hominids lived on foods that could be picked or gathered: plants, fruits, invertebrate animals such as ants and termites, and even occasional pieces of meat (perhaps hunted in the same manner as chimpanzees do today).
After 2.5 million years ago, meat seems to become more important in early hominids' diet. Evolving hominids' new interest in meat is of major importance in paleoanthropology.
Out on the savanna, it is hard for a primate with a digestive system like that of humans to satisfy its amino-acid requirements from available plant resources. Moreover, failure to do so has serious consequences: growth depression, malnutrition, and ultimately death. The most readily accessible plant resources would have been the proteins accessible in leaves and legumes, but these are hard for primates like us to digest unless they are cooked. In contrast, animal foods (ants, termites, eggs) not only are easily digestible, but they provide high-quantity proteins that contain all the essential amino acids. All things considered, we should not be surprised if our own ancestors solved their "protein problem" in somewhat the same way that chimps on the savanna do today.
Increased meat consumption on the part of early hominids did more than merely ensure an adequate intake of essential amino acids. Animals that live on plant foods must eat large quantities of vegetation, and obtaining such foods consumes much of their time. Meat eaters, by contrast, have no need to eat so much or so often. Consequently, meat-eating hominids may have had more leisure time available to explore and manipulate their environment, and to lie around and play. Such activities probably were a stimulus to hominid brain development.
The importance of meat eating for early hominid brain development is suggested by the size of their brains:
- cranial capacity of largely plant-eating Australopithecus ranged from 310 to 530 cc;
- cranial capacity of primitive known meat eater, Homo habilis: 580 to 752 cc;
- Homo erectus possessed a cranial capacity of 775 to 1,225 cc.
Hunters or scavengers?Edit
The archaeological evidence indicates that Oldowan hominids ate meat. They processed the carcasses of large animals, and we assume that they ate the meat they cut from the bones. Meat-eating animals can acquire meat in several different ways:
- stealing kills made by other animals;
- by opportunistically exploiting the carcasses of animals that die naturally;
- by hunting or capturing prey themselves.
There has been considerable dispute among anthropologists about how early hominids acquired meat. Some have argued that hunting, division of labor, use of home bases and food sharing emerged very early in hominid history. Others think the Oldowan hominids would have been unable to capture large mammals because they were too small and too poorly armed.
Recent zooarchaeological evidence suggests that early hominids (after 2.5 million years ago) may have acquired meat mainly by scavenging, and maybe occasionally by hunting.
If hominids obtained most of their meat from scavenging, we would expect to find cut marks mainly on bones left at kill sites by predators (lions, hyenas). If hominids obtained most of their meat from their own kills, we would expect to find cut marks mainly on large bones, like limb bones. However, at Olduvai Gorge, cut marks appear on both kinds of bones: those usually left by scavengers and those normally monopolized by hunters. The evidence from tool marks on bones indicates that humans sometimes acquired meaty bones before, and sometimes after, other predators had gnawed on them.
During decades of work at Olduvai Gorge, Mary and Louis Leakey and their team laid bare numerous ancient hominid sites. Sometimes the sites were simply spots where the bones of one or more hominid species were discovered. Often, however, hominid remains were found in association with concentrations of animal bones, stone tools, and debris.
At one spot, in Bed I, the bones of an elephant lay in close association with more than 200 stone tools. Apparently, the animal was butchered here; there are no indications of any other activity.
At another spot (DK-I Site), on an occupation surface 1.8 million years old, basalt stones were found grouped in small heaps forming a circle. The interior of the circle was practically empty, while numerous tools and food debris littered the ground outside, right up to the edge of the circle.
Earliest stone industryEdit
Use of specially made stone tools appears to have arisen as result of need for implements to butcher and prepare meat, because hominid teeth were inadequate for the task. Transformation of lump of stone into a "chopper", "knife" or "scraper" is a far cry from what a chimpanzee does when it transforms a stick into a termite probe. The stone tool is quite unlike the lump of stone. Thus, the toolmaker must have in mind an abstract idea of the tool to be made, as well as a specific set of steps that will accomplish the transformation from raw material to finished product. Furthermore, only certain kinds of stone have the flaking properties that will allow the transformation to take place, and the toolmaker must know about these.
Therefore, two main components to remember:
- Raw material properties
- Flaking properties
The oldest Lower Palaeolithic tools (2.0-1.5 million years ago) found at Olduvai Gorge (Homo habilis) are in the Oldowan tool tradition. Nevertheless, older materials (2.6-2.5 million year ago) have recently been recorded from sites located in Ethiopia (Hadar, Omo, Gona, Bouri - Australopithecus garhi) and Kenya (Lokalalei).
Because of a lack of remarkable differences in the techniques and styles of artifact manufacture for over 1 million years (2.6-1.5 million years ago), a technological stasis was suggested for the Oldowan Industry.
The makers of the earliest stone artifacts travelled some distances to acquire their raw materials, implying greater mobility, long-term planning and foresight not recognized earlier.
Oldowan stone tools consist of all-purpose generalized chopping tools and flakes. Although these artifacts are very crude, it is clear that they have been deliberately modified. The technique of manufacture used was the percussion.
The main intent of Oldowan tool makers was the production of cores and flakes with sharp-edges. These simple but effective Oldowan choppers and flakes made possible the addition of meat to the diet on a regular basis, because people could now butcher meat, skin any animal, and split bones for marrow.
Overall, the hominids responsible for making these stone tools understood the flaking properties of the raw materials available; they selected appropriate cobbles for making artifacts; and they were as competent as later hominids in their knapping abilities.
Finally, the manufacture of stone tools must have played a major role in the evolution of the human brain, first by putting a premium on manual dexterity and fine manipulation over mere power in the use of the hands. This in turn put a premium in the use of the hands.
Early hominid behaviorEdit
During the 1970s and 1980s many workers, including Mary Leakey and Glynn Isaac, used an analogy from modern hunter-gatherer cultures to interpret early hominid behavior of the Oldowan period (e.g., the Bed I sites at Olduvai Gorge). They concluded that many of the sites were probably camps, often called "home bases", where group members gathered at the end of the day to prepare and share food, to socialize, to make tools, and to sleep.
The circular concentration of stones at the DK-I site was interpreted as the remains of a shelter or windbreak similar to those still made by some African foraging cultures. Other concentrations of bones and stones were thought to be the remains of living sites originally ringed by thorn hedges for defense against predators. Later, other humanlike elements were added to the mix, and early Homo was described as showing a sexual division of labor [females gathering plant foods and males hunting for meat] and some of the Olduvai occupation levels were interpreted as butchering sites.
Views on the lifestyle of early Homo began to change in the late 1980s, as many scholars became convinced that these hominids had been overly humanized.
Researchers began to show that early Homo shared the Olduvai sites with a variety of large carnivores, thus weakening the idea that these were the safe, social home bases originally envisioned.
Studies of bone accumulations suggested that H. habilis was mainly a scavenger and not a full-fledged hunter. The bed I sites were interpreted as no more than "scavenging stations" where early Homo brought portions of large animal carcasses for consumption.
Another recent suggestion is that the Olduvai Bed I sites mainly represent places where rocks were cached for the handy processing of animal foods obtained nearby. Oldowan toolmakers brought stones from sources several kilometers away and cached them at a number of locations within the group's territory. Stone tools could have been made at the cache sites for use elsewhere, but more frequently portions of carcasses were transported to the toolmaking site for processing.
Current interpretations of the subsistence, settlement, and tool-use patterns of early hominids of the Oldowan period are more conservative than they have been in the past. Based upon these revised interpretations, the Oldowan toolmakers have recently been dehumanized.
Although much more advanced than advanced apes, they still were probably quite different from modern people with regard to their living arrangements, methods and sexual division of food procurement and the sharing of food.
The label human has to await the appearance of the next representative of the hominid family: Homo erectus.