The stone masters: toolmakers at work and children at play reflect ancient technology.

In the Indonesian island village of Langda, located on Irian Jaya near its border with Papua New Guinea, a half-dozen men sit in an open space, chipping fragments out of rocks. It's not rocket science, but it's a veritable rock science still practiced by a handful of groups around the world. The men are making double-edged stone blades for adzes, scythe-like tools with wooden handles that the Langda have traditionally used to clear land and to work wood. Several of the men show great dexterity in shaping stones into implements, a process known as stone or flint knapping. Each man holds a grapefruit-size stone in his right hand that he uses as a hammer to strike a rock braced against a piece of driftwood with his left band.

Deitrich Stout, an anthropology graduate student at Indiana University in Bloomington, sits among the men. To him, the situation is the next best thing to traveling back in time to witness what otherwise would be a lost art.

The men's work is going well. One craftsman proclaims his joy by crying out the name of a mythical figure revered as the provider of adze-worthy stone. A second man smiles and describes the stone strips, or flakes, that he's pounding from a blade as "peeling off like sweet potato skin." A third experienced adze maker talks excitedly of wanting to slice flakes off "every stone in the river."

Their duties encompass more than knapping stones. The skilled workers pause periodically to monitor and advise apprentices gamely pounding at their own potential blades. "Work more slowly," they might say. Or they might offer advice on proper knapping technique and posture or outline strategies for shaping a particular stone.

To Stout, the opportunity to observe interactions between the master stone workers of Langda and their apprentices may help him and other scientists recognize the handiwork of experts and apprentices on stone artifacts dating back thousands and perhaps even millions of years. And it could provide a window on the way ancient technological skills passed from generation to generation.

"Stone tools provide hard evidence of skilled performance that will be invaluable for determining when and how the social learning of tool making emerged," Stout says.

His research, published in the December 2002 Current Anthropology, appears at a time of ferment in investigations of both ancient and modern toolmakers. Some archaeologists now see a surprising amount of technical aptitude and regional variability in the earliest known examples of stone-tool fabrication and use. These observations challenge the traditional notion that knapping practices evolved slowly and uniformly, steadily increasing in complexity as time passed.

What's more, psychologists who study how children develop motor abilities (SN: 3/20/99,p. 184) have been weighing in on ancient tool use. They're finding that toddlers learn to use toy tools on their own by exploiting well-practiced hand and arm actions from infancy combined with the added freedom of hand movement that comes with standing upright. If 1-year-olds can walk their way toward simple types of tool use, then founding members of the human evolutionary family--who adopted a two-legged stride perhaps 8 million years ago--could have done so as well, these researchers suggest.

ROCK ON In the fall of 1999, a group of five expert and five apprentice Langda adze makers welcomed Stout into their fold. They were flattered that an outsider wanted to observe a craft that they regard with great pride.

The process begins with a trek down a steep valley to a river, where seasoned workers select promising boulders. They strike small chunks from the best candidates to look for a uniform grain under the surface and other signs of internal strength. When they uncover the best boulders, the stone workers crack them open using a set of hammering stones, sometimes also relying on the heat of a fire to weaken the boulders.

This yields large hunks that then need to be reduced to stones suitable for carrying back to their village for knapping. There, after flaking a stone into the general shape of a blade, the nearly complete tool is ground against a sandstone slab for an hour or more. Then, it's ready to be bound to an adze handle's socket with rattan strips.

As Stout observed this sequence, he realized that the experts--who had passed through apprenticeships of 5 to 10 years--made a different breed of adze blades than novices did. Experts removed long, thin flakes from a budding blade, yielding a smooth surface and a shape that looked much the same from one product to the next. These craftsmen fashioned large, long blades that gracefully tapered to a point. Most of their blades extended 8 inches or more.

In contrast, apprentices scooped out short, thick flakes from stones, leading to a scalloped finish. They also skipped certain knapping procedures that were too difficult for them. These aspiring craftsmen ended up with fairly short, wide blades, most no longer than 6 inches. Points were unevenly shaped and varied greatly from piece to piece.

The main reasons for these differences boiled down to execution and experience, Stout says. Experts first homed in on the best ridges jutting out from a stone from which to strike flakes and then wielded their hammers with remarkable precision and deftness.

This is not just a job to the craftsmen. They see it as a social bond with their environment in which they nurture an ongoing relationship with living stones, Stout notes. In traditional societies, practical knowledge about plants, thunderstorms, and other features of the natural world commonly includes an assumption that these objects and events are alive (SN: 6/5/99, p. 360). For instance, knappers take care not to anger pieces of stone through practices deemed to be improper or careless, such as failing to place finished blades parallel on the ground, with sharp points facing away from the worker. Langda adze makers also emphasize their social links to dead and mythical ancestors who they say handed down their craft through the generations.

Like Langda stone workers, Stone Age toolmakers may also have consisted of experts and apprentices, Stout says. For instance, it must have required years of practice to become adept at making the teardrop-shaped hand axes of the so-called Acheulian tradition, which flourished around 500,000 years ago.

Communities of expert practitioners and apprentices represent, in Stout's view, "a distinctive cultural mode of skill acquisition that has emerged over the course of human evolution."

The trick to supporting this view, says archaeologist John A.J. Gowlett of the University of Liverpool in England, will be to work backward from the realm of Langda tool makers and other modern artisans into the world of Stone Age tool specialists.

BEAD CRAFTERS Stout's observations of the Langda adze makers resonate with the findings of a team of French archaeologists and motion researchers who have studied stone-bead knappers Khambhat, a region of northern India.

Led by Blandine Bril of the School of Higher Studies in Social Sciences in Paris and Valentine Roux of the National Center of Scientific Research in Nanterre, the scientists studied 12 craftsmen: 6 had trained for 7 to 10 years at traditional bead-making centers and 6 had trained for 2 to 3 years at less demanding workshops that have recently emerged to fill the international demand for high-quality stone jewelry.

Bead knapping uses two tools--a sharp-pointed iron bar sticking up from the ground in front of the artisan and a hammer made from a cylindrical buffalo horn attached to a thin wooden stick. A small piece of stone is pressed against the bar's point and then struck from above with the hammer. The force of the blow drives the point into the rock, detaching a flake.

With this technique, craftsmen remove pieces of stone in set sequences that vary according to the shapes of the beads they want to make.

Comparison of these bead makers and the Langda knappers showed many similarities. The highly trained bead makers produced longer, larger beads than did their lesser-trained peers. Experts carried out delicate knapping operations that the others didn't perform, apparently because the latter lacked the skill to do so.

Bead makers with the most training were far more successful than the others at fashioning the barrel-shaped beads prized in the region. Moreover, when the researchers provided the bead makers with glass, a substance with which they had not previously worked, only the experts successfully knapped it.

Measurements of hammer acceleration and trajectory showed that the experts fine-tuned and adapted their strokes based on a bead's raw material and the size of the flake they wanted to detach.

These data from modern bead makers yield insights into stone beads found among the remains of India's ancient Harrapan culture. Harrapan society reached its peak around 4,500 to 4,900 years ago. Most Harrapan beads are small and irregularly shaped. However, several hundred long, barrel-shaped beads, which resemble those made by the present day Khambhat bead makers, have also been unearthed.

"Harrapan long beads were made by highly skilled craftsmen who developed specialized skills for a very limited demand, although their products were quite valuable," Bril says. A small number of proficient Harrapan craftsmen--perhaps only one or two--must have produced all the barrel-shaped beads, she and Roux surmise.

During that era, researchers have found, the use of the potter's wheel and other techniques requiring complex skills and years of apprenticeship were also spreading through Harrapan society.

INNOVATIVE ACTS Despite such findings, scientists have much to learn about prehistoric toolmaking, remarks archaeologist Sophie De Beaune of Jean Moulin University in Paris.

Just as studies of modern-day stone workers may give scientists an edge in understanding ancient toolmakers, so might investigations of tool use in animals and infant humans.

Consider that extended apprenticeships in tool use might well have emerged in ancient apes before appearing in members of the human evolutionary family. In groups of modern chimpanzees that crack nuts with a stone hammer and an anvil, juvenile animals spend several years learning the technique from experienced adults. The juveniles primarily imitate adults' tool use rather than the adults' providing direct guidance to novices. Still, chimps pass through a "kind of apprenticeship' in which they learn to execute the hand and arm movements needed for cracking nuts, De Beanne holds.

Her evolutionary scenario fits into the growing conviction that as early as 8 million years ago, human ancestors must have used unmodified stones as tools. Later, groups began chipping edges on stones and leaving them behind in communal workspaces, which scientists have excavated, Melissa A. Panger of George Washington University in Washington, D.C., and her colleagues suggested last year in Evolutionary Anthropology (2002, vol. 11, issue 6). Those artifacts date to no earlier than about 2.5 million years ago.

Intriguingly, several 2.5-million-to-2.3-million-year-old African sites have yielded stone artifacts that exhibit signs of sophisticated knapping techniques and toolmaking styles adapted to local rock characteristics, according to Erella Hovers of the Hebrew University in Jerusalem. Hovers takes this as evidence that early toolmakers responded to whatever material they had to work with, rather than making do with a generic approach.

De Beaune agrees. She also suspects that the first anatomically modern humans, who lived at least 200,000 years ago, had all the manual capabilities of people today. In a revolving process of innovation, ancient groups made tools for specific tasks with available materials, invented novel uses for those tools, and then created more intricate implements to meet their new needs more efficiently, De Beaune proposes.

Infants do something similar as they grow, says psychologist Jeffrey J. Lockman of Tulane University in New Orleans. Babies' routine efforts to explore the world set up their later tool use, in his view. That counters the stance of many researchers who hold that childhood tool use emerges during the second year of life from an insight that certain objects can provide a means to an end.

The banging or pounding of objects provides a telling example Lockman finds that by 7 months of age, infants who previously pounded all sorts of items show a preference for banging pairs of hard cubes--either singly against a hard surface or together--rather than soft cubes. By 8 to 10 months of age, babies begin to choose hard mallets over soft ones, picking them up by the handles before pounding away. However, only after age 1 year do they deliberately seek out tools to pound with.

Childhood tool use blossoms with the emergence of stable hand preferences and an upright posture, says Daniela Corbetta of Purdue University in West Lafayette, Ind. Before they start to crawl, infants learn on their own to use both hands in systematic ways to open toy boxes or complete other tasks, Corbetta finds. This behavior disappears when the same infants begin crawling and reappears after they've been walking for a few months. Right- or left-handedness then develops, with the dominant hand achieving better fine motor skills and greater strength.

"Efficient stone knapping can only emerge as the result of developing both an upright posture and stable hand-use preferences," Corbetta proposes. This practice may thus be unique to members of the human evolutionary family, all of whom have possessed a two-legged gait.

Still, for our stone-tool-inclined ancestors, it wasn't enough to walk the walk. They had to learn how to sock the rock.