The Ages of Stone and Clay

The High Priest of Kulaba formed some clay and wrote words on it as if on a tablet — In those days words written on clay tablets did not exist, But now, with the sun's rising, so it was! The High Priest of Kulaba wrote words as if on a tablet, and so it was!

— Enmerkar and the Lord of Arratá

Gazing across the stark, sunbaked land- and waterscape of Salmon Creek Reservoir, set in the sagebrush desert of southern Idaho, I was alert to any motion of the tip of my fishing pole, propped up by rocks. My family and I often visit my in-laws in Twin Falls, Idaho, and we always go fishing for rainbow trout. Erik, my younger son, back from exploring the barren cliffs, came running up to me, clutching a black stone different in appearance from the slabs of lava rock scattered along the shore about us.

"Dad, what's this?"

Turning the dull stone over in my hand, I told him it was obsidian. "It's glass — different from most rocks. More like a frozen liquid than a crystalline solid." When I started to explain that it had a different atomic structure than many other minerals, his gaze drifted away. I turned and threw the piece of obsidian against a nearby rock, shattering it into shiny, razor-edged chunks. "Native Americans around here and people in the ancient Near East used obsidian to make axes and arrowheads, because it splits into lots of sharp pieces." Glass is one of many materials that craftspeople used thousands of years ago that we still employ, albeit in very different ways. I told Erik that today phone companies were replacing copper wires with optical fibers made of very pure and ultra-clear glass.

"Well," Erik asked, perhaps less concerned with these facts than the rock he had found, "why is obsidian black?"

"Clear glass is made from silicon, oxygen, sodium, and calcium," I replied. "But obsidian contains dirt, small amounts of other atoms that make it black. The first people could make tools out of rocks like this, which is why we humans did so well. Glass was as high tech ten thousand years ago as it is today." Satisfied, Erik checked his rod and went off to look for other rocks.

A few days later, we were looking out across a large moraine at the spectacular vistas in Rocky Mountain National Park. Once the basin before us was clogged with glacial debris — large boulders and rocks — now hardly to be seen, though the U-shaped valley is the signature of a glacier melted long ago. The displays in the park exhibit at Moraine Basin remind visitors that rocks erode because slightly acidic water attacks the cement that holds minerals together. Most rocks do not have a uniform structure like obsidian, but are composites of several different constituents, similar to concrete, an artificial pourable stone, in which mortar bonds together sand and hard rocks. In nature, heavy loads are always supported by composite structures, not homogeneous materials. Mimicking nature, humans also use composite materials for their most advanced applications. We'll learn why later. First let's turn to the earliest tales of materials.

Early humans faced overwhelming obstacles to survival. They needed food for sustenance, weapons against predators — both animal and human — and shelter from an often brutal environment. In their desperate struggle, our ancestors came to realize that the gray-brown-black rocks they found scattered about them were useful for making weapons and tools; flint and obsidian were particularly desirable. Anthropologists have uncovered the earliest evidence of stone implements in the Rift Valley of East Africa. More than two million years ago, humans were first finding ways to master nature, and the earliest stone artifacts discovered in the Olduvai Gorge consisted of flakes, or thin chips, and the stones from which they were struck. No one yet knows what these stone implements were used for, although the fact they were frequently found near bone fragments suggests that our ancestors used them to butcher animals, ranging in size from elephants and hippopotami to rodents and tortoises. Sharp flakes could slice through tough hides, while stones broke open bones to get at the marrow. Since anthropologists believe the diet of these early folk was more than half vegetarian, they likely also used stone tools to dig up roots and tubers, and crack open hard-shelled nuts.

Perhaps not coincidentally, the separation of the genus Homo (man) from Australopithecus (southern ape) occurred at approximately the same time as the first appearance of simple stone tools. It is still unclear whether Homo fashioned rudimentary tools and Australopithecus did not; it is conceivable, however, that the ability to make tools gave Homo an advantage in the battle for survival over Australopithecus, which eventually became extinct. Nevertheless, Homo survived for other reasons, including the sharing of responsibility for gathering wild plants and hunting game. Cooperation within a hunter-gatherer group was the first step toward the specialization in crafts leading to innovations in both their world and, ultimately, ours.

Early development of simple collections of stone implements — or tool kits, as they are called — appears to have taken place entirely in Africa and progressed at a very slow pace, because food was readily available. Where there was enough to eat, there was no need to innovate. Pressure on the food supply by an increasing population forced these early folk to develop new and better ways to hunt and gather food. It was during the Lower Paleolithic period that early humans spread out of Africa to parts of Asia and Europe, perhaps 1.5 million years ago. At about this time, the ancestor of modern humans, the species Homo erectus (man who walks upright) emerged. Homo erectus, with a brain larger than such predecessors as Australopithecus, walked with a striding gait and differed from modern humans primarily through its larger jaws and teeth. With additional enlargement of its brain and changes in facial structure, a new species, Homo sapiens (wise man), appeared around 250,000 years ago. Further division into subspecies occurred, including the famed Homo sapiens neanderthalensis and culminating in Homo sapiens sapiens, modern humans who emerged 100,000 years ago, and who replaced all other human types on earth by approximately 30,000 years ago.

Among our ancestors' tools, hand axes — large cutting implements with two planar faces meeting at a shallow angle — were the primary product of...