Clues to Man : Researchers Try Hand at Toolmaking
When two scientists, working separately in Africa and in Peru, recently came up with some new insights about the development of stone tools, their pioneering work not only sparked new interest in the evolution of toolmaking but also underscored a new trend in archeology that has potentially far-reaching ramifications.
No longer are researchers content merely to dig for artifacts. Instead, some are actually learning the techniques of making and then using stone tools themselves--just like the ancient peoples they are studying--in order to base their hypotheses on first-hand knowledge. Increasingly, they are, in effect, performing experiments and using controlled observations.
The growing practice already is yielding new insights about how our ancestors made and used stone tools. The development of tools is important because it marks a major transition in the evolution from animal to human.
New Insights
Chief among the new insights is the emerging recognition that artifacts many modern archeologists had assumed to be tools because of their shapes were actually debris left behind in the manufacture of tools and that flakes of stone they had assumed to be debris were actually the tools.
In addition, such insights also may lead to new understanding about how the human brain works--or more precisely, why 90% of humans are right-handed and when humans developed the power of speech.
“The more you do this type of experimental approach to archeology,” said Nicholas Toth of UC Berkeley’s Institute of Human Origins, “the greater will be your ability to interpret prehistoric patterns. You see patterns that would not have emerged had you not done that type of work.”
The shaping of stones with other stones is the oldest technology known. More than 2 million years ago, prehistoric man was pounding stone against stone to produce tools for cutting, scraping, and breaking.
Inca Techniques
As recently as the 16th Century, Incas in South America used stones as tools in the construction of walls, buildings, and temples.
Toth has been investigating the manner in which Stone Age man used stones as tools and Jean-Pierre Protzen, also of UC Berkeley, has been studying how the Incas built stone structures with stone tools and limited manpower.
Toth’s findings about Stone Age man, many experts feel, may spark a renewed study of how toolmaking technology developed, while Protzen’s findings about the Incas should eliminate once and for all many fanciful theories--such as that the Incas were able to build massive stone structures because they had developed chemicals that would dissolve rocks or because they were taught technology by visiting “astronauts.”
Toth’s work has focused primarily on the era about 2 million years ago in which human ancestors known as hominids first began using stone tools extensively.
Excavations from that era generally reveal assemblages of perhaps a half dozen different types of so-called “core tools” fashioned by removal of flakes from cobblestones. Based on their shapes, these core tools are generically called choppers, scrapers, and so forth. Excavations from more recent periods typically reveal a larger variety of core tools.
Influenced by the work of Mary Leakey at Olduvai Gorge in Tanzania, scientists have generally considered these core tools to be the principal tools used by hominids. Museum reconstructions and paintings typically show hominids bending over animal carcasses with a bloody core tool in hand.
Emphasis Questioned
But, Toth said in a telephone interview, “too much emphasis has been placed on the core tools . . . as definite end products of manufacture. I think a lot of these (core tools) are actually byproducts of the manufacture of flakes,” which were much more valuable to the hominids.
Rick Potts of the Smithsonian Institution noted that archeologists are carrying out more field work such as Toth’s because “we want to get away from guesses about the plausibility” of prehistoric behavior and achieve a more soundly grounded knowledge of what actually went on.
Toth agreed. “Many people were developing ideas along those lines,” he said, “but they didn’t have the experimental (results) to back up any of those ideas. It was more along the lines of ‘armchair speculation.’ ”
Toth spent the better part of five years in Africa making and using these tools, “looking for the types of evidence we can’t find in the prehistoric record.” Those studies were supplemented by laboratory analyses of prehistoric tools and by observation of modern hunter-gatherer cultures and of chimpanzees, which “are the world’s second-best toolmakers after man.”
Making stone tools is not as simple as it might seem. The selection of the proper angle for striking the cobble with a hammerstone is especially crucial, and it is necessary to use a powerful but controlled glancing blow. Once he had taught himself the technique, Toth made thousands of tools from cobbles similar to those to which the hominids had access.
Toth’s key observation, reported in a recent issue of the Journal of Archaeological Science, was that the “tools” previously identified by archeologists evolved naturally as flakes were produced. The major factor in determining the shape of the core tools was simply the shape of the cobble from which it was made. A wedge-shaped cobble, for example, yielded a “chopper” after only a couple of flakes had been removed.
Toth also found that the flakes were, in general, more useful than the core tools for a wide variety of tasks that he attempted, including bone breaking, hide working, woodworking, grass cutting, and animal butchery (using animals that had died of natural causes). “I had no trouble even butchering the hide of an elephant,” he said.
“I think the flakes that were struck from these pebbles were at least as important as, if not more important than, the core tools based on my experience,” Toth said.
This hypothesis was supported by other evidence. Toth and Lawrence Keeley of the University of Illinois had previously developed a technique for identifying how tools had been used based on the “polish” that is left on their surfaces. Unfortunately, the technique works best with tools made from crystalline silica, and does not work with the lava that was most commonly used in the Lake Turkana region of Kenya that Toth studied.
Signs of Use
Nonetheless, he was able to accumulate 55 crystalline artifacts, tools, and flakes from the site and analyze them. Only nine showed clear signs of use, and all nine were flakes or flake fragments.
Toth has also examined the scratches left on bones by prehistoric tools and concluded that most were left by flakes rather than by the core tools.
An interesting sidelight of Toth’s experiments is that it casts light on when the phenomenon of right-handedness evolved. “This is a question that psychologists and neurologists have been discussing for over a century,” Toth said. About 90% of humans are right-handed, whereas handedness does not appear in even our closest animal relatives.
Handedness is important because it indicates the “lateralization” of the brain, in which the left hemisphere controls the right hand, and the right hemisphere controls the left hand. Language is also controlled by the left hemisphere, and many scientists believe that speech did not evolve until after the brain became lateralized--and thus after right-handedness evolved.
In his field studies, Toth observed that he produced slightly more flakes that have a crescent of the weathered surface of the cobble on the right. This occurs because the right-handed individual typically holds the cobble in the more passive left hand, and muscular coordination generally makes that hand turn the rock in a clockwise direction.
Left-handers do the reverse and typically produce more flakes with the crescent on the left.
Toth produced about 56% right-handed flakes and 44% left-handed. The bias is not larger, he explained, because the shape of the cobble often dictates which hand must be used.
Flakes from the sites at Lake Turkana were about 57% right-handed and 43% left-handed. At a site in Spain that is only about 250,000 years old, the proportions were 61% right-handed and 39% left-handed.
Toth thus concludes that even as long ago as 2 million years, man was predominantly right-handed. More important, he added, the technique can now be applied to earlier sites to get a better idea of precisely when right-handedness developed.
Toth’s work has been generally well accepted by his colleagues.
His hypothesis is also being supported by the discoveries of other investigators. Last week, for example, a team of scientists headed by Noel T. Boaz of the Virginia Museum of Natural History and Alison S. Brooks of George Washington University announced that they had uncovered a cache of about 300 tools at a site along the Semliki River in eastern Zaire.
The tools had an estimated age of about 2.3 million years, making them among the oldest specimens discovered. “Nearly 95% of the tools were flakes,” Brooks said in a telephone interview, “and virtually all of them showed signs of use, although we haven’t yet had time to examine them under a microscope to see what they were used for.”
Another scientist who firmly believes in participatory archeology is Protzen, chairman of the department of architecture at UC Berkeley. On a trip from Brazil to the United States in 1979, Protzen stopped in Peru to visit sites where, in the 15th and 16th centuries, the Incas had erected various structures without benefit of iron tools or mortar.
“Stone blocks weighing as much as 220,000 pounds were fitted so closely to their neighbors that even now a knife blade cannot be inserted into many of the joints,” Protzen wrote in the February Scientific American.
“When I asked my guides how the Incas had shaped the stones,” he said in a telephone interview, “they gave me vague answers that provided no insight. Even when I returned to this country and consulted archeologists, they told me they did not know how it was done.”
Ancient Rock Quarries
Intrigued, Protzen made four return visits to the Cuzco environs of south central Peru, during which he visited several Inca settlements and the rock quarries that had supplied building materials for them. Several of the quarries had been used up to the present day, but one had been virtually untouched since it was abandoned by the Incas.
Protzen observed that cuplike depressions on the Inca stones were very similar to marks on an obelisk from Aswan in Egypt. “It is known that the Egyptians shaped their stones by pounding away at the work piece with balls of (rock),” he wrote. “It seems reasonable to think the Incas did the same thing.”
Searching the quarries, Protzen found some rounded stones of quartzite, a type of sandstone that did not occur at the quarry, but that was present in the nearby Urubamba River. Those stones had pit marks on the end, indicating they were used for pounding.
He then attempted to manufacture building blocks himself. In one case, for example, he chose a block of andesite--a volcanic rock--and used a large quartzite stone weighing about 20 pounds to give it a roughly rectangular shape. He next took an eight-pound quartzite stone that fit comfortably in both hands and began chipping away pieces to flatten one surface.
The resilience of the stone caused it to bounce back into the air, so that minimal effort was required for this step.
This hammer proved to be too big for completing the edges of the block, so he used a smaller stone that weighed about a pound. With this technique, he wrote, “the entire process, from squaring the block to drafting five (of 12) edges and finishing three (of six) sides took no more than 90 minutes.”
His experience, he continued, “shows that stones can be mined, cut, and dressed (flattened) using simple tools in a way that takes little time or effort.” Larger blocks could be fashioned in the same manner.
“The physical evidence that the Incas used techniques similar to mine is abundant,” Protzen wrote. All of the stones he examined, regardless of the type of rock, showed scars similar to those he produced in his work, for example. If the block is limestone, there is a whitish discoloration at the scar, “undoubtedly . . . resulting from the heat generated by the impact of the hammerstone.”
And finally, in all cases, the scars were smaller toward the edge of the stone than in the center, “which suggests that hammers used to work the edge were smaller than those used on the center of the face.”
The problem of building walls without mortar was apparently solved by constructing blocks that fit together almost in the manner of the plastic building blocks used by children. The tops of blocks in each row of stone would be given a concave indentation.
Fitted Stones
The bottoms of the next row of rocks would then be given a convex shape that would fit into the depression exactly. This process undoubtedly proceeded by a number of trial-and-error fittings.
One indication of the stability of walls produced in this manner is provided by the Church of Santo Domingo in Cuzco, which was built with modern techniques. An earthquake in the early 1950s toppled the church, but an Inca fitted-stone wall on which the church was built remained intact.
Even though Protzen is not an archeologist, members of that fraternity have accepted his findings. Protzen’s work, according to Christopher Donnen of UCLA, is “the best collection of evidence and empirical testing of techniques that has ever been done in studying Inca architecture.”
