Asimov's New Guide to Science

by Isaac Asimov

  EARLY CIVILIZATIONS

  Documented human history, as recorded by Greek historians, was no better, or more ancient than that of the Bible. It began only about 700 B.C. Beyond this hard core of history, dim oral traditions went back to the Trojan War, about 1200 B.C., and more dimly still to a pre-Greek civilization on the island of Crete under a King Minos. Nothing beyond the writings of historians in known languages, with all the partiality and distortion that might involve—was known to moderns concerning the everyday life of ancient times prior to the eighteenth century. Then, in 1738, the cities of Pompeii and Herculaneum, buried in an eruption of Vesuvius in 79 A.D., began to be excavated. For the first time, historians grew aware of what could be done by digging, and the science of archaeology got its start.

  At the beginning of the nineteenth century, archaeologists began to get their first real glimpses of human civilizations that came before the periods described by the Greek and Hebrew historians. In 1799, during General Bonaparte’s invasion of Egypt, an officer in his army, named Boussard, discovered an inscribed stone in the town of Rosetta, on one of the mouths of the Nile. The slab of black basalt had three inscriptions, one in Greek, one in an ancient form of Egyptian picture writing called hieroglyphic (“sacred writing”), and one in a simplified form of Egyptian writing called demotic (“of the people”).

  The inscription in Greek was a routine decree of the time of Ptolemy V, dated the equivalent of 27 March 196 B.C. Plainly, it must be a translation of the same decree given in the other two languages on the slab (compare the no-smoking signs and other official notices that often appear in three languages in public places, especially airports, today). Archaeologists were overjoyed: at last they had a “pony” with which to decipher the previously undecipherable Egyptian scripts. Important work was done in “cracking the code” by Thomas Young, the man who had earlier established the wave theory of light (see chapter 8), but it fell to the lot of a French student of antiquities, Jean Francois Champollion, to solve the Rosetta stone completely. He ventured the guess that Coptic, a still-remembered language of certain Christian sects in Egypt, could be used as a guide to the ancient Egyptian language. By 1821, he had cracked the hieroglyphs and the demotic script and opened the way to reading all the inscriptions found in the ruins of ancient Egypt.

  An almost identical find later broke the undeciphered writing of ancient Mesopotamia. On a high cliff near the ruined village of Behistun in western Iran, scholars found an inscription that had been carved about 520 B.C. at the order of the Persian emperor Darius I. It announced the manner in which he had come to the throne after defeating a usurper; to make sure that everyone could read it, Darius had had it carved in three languages—Persian, Sumerian, and Babylonian. The Sumerian and Babylonian writings were based on pictographs formed as long ago as 3100 B.C. by indenting clay with a stylus; these had developed into a cuneiform (“wedge-shaped”) script, which remained in use until the first century A.D.

  An English army officer, Henry Creswicke Rawlinson, climbed the cliff, transcribed the entire inscription, and, by 1846, after ten years of work, managed to work out a complete translation, using local dialects as his guide where necessary. The deciphering of the cuneiform scripts made it possible to read the history of the ancient civilizations between the Tigris and the Euphrates.

  Expedition after expedition was sent to Egypt and Mesopotamia to look for tablets and the remains of the ancient civilizations. In 1854, a Turkish scholar, Hurmuzd Rassam, discovered the remnants of a library of clay tablets in the ruins of Nineveh, the capital of ancient Assyria—a library that hac! been collected by the last great Assyrian king, Ashurbanipal, about 650 B.C. In 1873, the English Assyriologist George Smith discovered clay tablets giving legendary accounts of a flood so like the story of Noah that it became clear that much of the first part of the book of Genesis was based on Babylonian legend. Presumably, the Jews picked up the legends during their Babylonian captivity in the time of Nebuchadnezzar, a century after the time of Ashurbanipal. In 1877, a French expedition to Iraq uncovered the remains of the culture preceding the Babylonian—that of the aforementioned Sumerians. This finding carried the history of the region back to earliest Egyptian times. And in 1921, remains of a totally unexpected civilization were discovered along the Indus Valley in what is now Pakistan. It had flourished between 2500 and 2000 B.C.

  Yet Egypt and Mesopotamia were not quite in the same league with Greece when it carne to dramatic finds on the origins of modern Western culture. Perhaps the most exciting moment in the history of archaeology carne in 1873 when a German ex-grocer’s boy found the most famous of all legendary cities.

  Heinrich Schliemann as a boy developed a mania for Homer. Although most historians regarded the Iliad as mythology, Schliemann lived and dreamed of the Trojan War. He decided that he must find Troy and, by nearly superhuman exertions, raised himself from grocer’s boy to millionaire so that he could finance the quest. In 1868, at the age of forty-six, he set forth. He persuaded the Turkish government to give him permission to dig in Asia Minor; and, following only the meager geographical clues afforded by Homer’s accounts, he finally settled upon a mound near the village of Hissarlik. He browbeat the local population into helping him dig into the mound. Excavating in a completely amateurish, destructive and unscientific manner, he began to uncover a series of buried ancient cities, each built on the ruins of the other. And then, at last, success: he uncovered Troy—or at least a city he proclaimed to be Troy. Actually, the particular ruins he named Troy are now known to be far older than Homer’s Troy, but Schliemann had proved that Homer’s tales are not mere legends.

  Inexpressibly excited by his triumph, Schliemann went on to mainland Greece and began to dig at the site of Mycenae, a ruined village which Homer had described as the once powerful city of Agamemnon, leader of the Greeks in the Trojan War. Again, Schliemann uncovered an astounding find—the ruins of a city with gigantic walls, which we now know to date back to 1500 B.C.

  Schliemann’s successes prompted the British archaeologist Arthur John Evans to start digging on the island of Crete, described in Greek legends as the site of a powerful early civilization under a King Minos. Evans, exploring the island in the 1890s, laid bare a brilliant, lavishly ornamented Minoan civilization that stretched back many centuries before the time of Homer’s Greece. Here, too, written tablets were found. They were in two different scripts, one of which, called Linear B, was finally deciphered in the 1950s and shown to be a form of Greek, through a remarkable feat of cryptography and linguistic analysis, by a young English architect named Michael Vestris.

  As other early civilizations were uncovered—the Hittites and the Mittanni in Asia Minor, the Indus civilization in India, and so on—it became obvious that the history recorded by Greece’s Herodotus and the Hebrews’ Old Testament represented comparatively advanced stages of human civilization. The earliest cities were at least several thousand years old, and the prehistoric existence of humans in less civilized modes of life must stretch many thousands of years farther into the past.

  THE STONE AGE

  Anthropologists find it convenient to divide cultural history into three major periods: the Stone Age, the Bronze Age, and the Iron Age (a division first suggested by the Roman poet and philosopher Lucretius and introduced to modern science by the Danish paleontologist Christian Jurgenson Thomsen in 1834). Before the Stone Age, there may have been a “Bone Age,” when pointed horns, chisel-like teeth, and c1ublike thigh bones served human beings at a time when the working of relatively intractable rock had not yet been perfected.

  The Bronze and Iron ages are, of course, very recent; as soon as we delve into the time before written history, we are back in the Stone Age. What we call civilization (from the Latin word for “city”) began perhaps around 8000 B.C., when humans first turned from hunting to agriculture, learned to domesticate animals, invented pottery and new types of tools, and started to develop permanent communities and a settled way of life. Beca
use the archaeological remains from this period of transition are marked by advanced stone tools formed in new ways, it is called the New Stone Age, or the Neolithic period; and although it antedated the supposed Biblical date of creation, humanity was already old at the time.

  This Neolithic Revolution seems to have started in the Near East, at the crossroads of Europe, Asia, and Africa (where later the Bronze and Iron ages also were to originate). From there, it appears, the revolution slowly spread in widening waves to the rest of the world. It did not reach western Europe and India until 3000 B.C., northern Europe and eastern Asia until 2000 B.C., and central Africa and Japan until perhaps 1000 B.C. or later. Southern Africa and Australia remained in the Old Stone Age until the eighteenth and nineteenth centuries. Most of America also was still in the hunting phase when the Europeans arrived in the sixteenth century, although a well-developed civilization, possibly originated by the Mayas, had developed in Central America and Peru as early as the first centuries of the Christian era.

  Evidences of humanity’s pre-Neolithic cultures began to come to light in Europe at the end of the eighteenth century. In 1797 an Englishman named John Frere dug up in Suffolk some crudely fashioned Hint tools too primitive to have been made by Neolithic human beings. They were found thirteen feet underground, which, allowing for the normal rate of sedimentation, testified to great age. In the same stratum with the tools were bones of extinct animals. More and more signs of the great antiquity of tool-making human beings were discovered, notably by two nineteenth-century French archeologists, Jacques Boucher de Perthes and Edouard Armand Lartet. Lartet, for instance, found a mammoth tooth on which some early human being had scratched an excellent drawing of the mammoth, obviously from living models. The mammoth was a hairy species of elephant that disappeared from the earth well before the beginning of the New Stone Age.

  Archaeologists launched upon an active search for early stone tools. They found that these could be assigned to a relatively short Middle Stone Age (Mesolithic) and a long Old Stone Age (Paleolithic). The Paleolithic was divided into Lower, Middle, and Upper periods. The earliest objects that could be considered tools (eoliths, or “dawn stones”) seemed to date back nearly a million years!

  What sort of creature had made the Old Stone Age tools? It turned out that Paleolithic human beings, at least in their late stages, was far more than a hunting animal. In 1879, a Spanish nobleman, the Marquis de Sautuola, explored some caves that had been discovered a few years earlier—after having been blocked off by rock slides since prehistoric times—at Altamira in northern Spain near the city of Santander. While he dug into the floor of a cave, his five-year-old daughter, who had come along to watch papa dig, suddenly cried: “Toros! Toros!” (“Bulls! Bulls!”). The father looked up, and there on the walls of the cave were drawings of various animals, in vivid color and vigorous detail.

  Anthropologists found it hard to believe that these sophisticated drawings could have been made by primitive people. But some of the pictured animals were plainly extinct types. The French archaeologist Henri Edouard Prosper Breuil found similar art in caves in southern France. All the evidence finally forced archaeologists to agree with Breuil’s firmly expressed views and to conclude that the artists must have lived in the late Paleolithic, say about 10,000 B.C.

  Something was already known about the physical appearance of these Paleolithic men. In 1868, workmen excavating a roadbed for a railroad had uncovered the skeletons of five human beings in the so-called Cro-Magnon caves in southwest France. The skeletons were unquestionably Homo sapiens, yet some of them, and similar skeletons soon found elsewhere, seemed to be up to 35,000 or 40,000 years old, according to the geological evidence. They were given the name Cro-Magnon man (figure 16.4). Taller than the average modern man and equipped with a large braincase, a Cro-Magnon man is pictured by artists as a handsome, stalwart fellow, modern enough, it would certainly appear, to be able to interbreed with present-day human beings.

  Figure 16.4. Reconstructed skulls of (A) Zinjanthropus, (B) Pithecanthropus, (C) Neanderthal, and (0) Cro-Magnon.

  Human beings, traced thus far back, were not a planet-wide species as they are now. Prior to 20,000 B.C. or so, they were confined to the great “world island” of Africa, Asia, and Europe. It was only later that hunting bands began to migrate across narrow ocean passages into the Americas, Indonesia, and Australia. It was not until 400 B.C., and later, that daring Polynesian navigators crossed wide stretches of the Pacific, without compasses, and in what were little more than canoes, to colonize the islands of the Pacific. Finally, it was not until the twentieth century that a human foot rested on Antarctica.

  But if we are to trace the fortunes of prehistoric peoples at a time when they were confined to only part of the earth’s land area, there must be some manner of dating events, at least roughly. A variety of ingenious methods have been used.

  Archaeologists have, for instance, used tree rings for the purpose, a technique (dendrochronology) introduced in 1914 by the American astronomer Andrew Ellicott Douglass. Tree rings are widely separated in wet summers when much new wood is laid down, and closely spaced in dry summers. The pattern over the centuries is quite distinctive. A piece of wood forming part of a primitive abode can have its ring pattern matched with the one place of the scheme where it will fit, and, in this way, its date can be obtained.

  A similar system can be applied to layers of sediment or varves laid down summer after summer by melting glaciers in such places as Scandinavia. Warm summers will leave thick layers, cool summers thin ones; and again, there is a distinctive pattern. In Sweden, events can be traced back 18,000 years in this way.

  An even more startling technique is that developed in 1946 by the American chemist Willard Frank Libby. Libby’s work had its origin in the 1939 discovery by the American physicist Serge Korff that cosmic ray bombardment of the atmosphere produced neutrons. Nitrogen reacts with these neutrons, producing radioactive carbon 14 in nine reactions out of every ten, and radioactive hydrogen 3 in the tenth reaction.

  As a result, the atmosphere would always contain small traces of carbon 14 (and even smaller traces of hydrogen 3). Libby reasoned that radioactive carbon 14 created in the atmosphere by cosmic rays would enter all living tissue via carbon dioxide, first absorbed by plants and then passed on to animals. As long as a plant or animal lived, it would continue to receive radiocarbon and maintain it at a constant level in its tissues. But when the organism died and ceased to take in carbon, the radiocarbon in its tissues would begin to diminish by radioactive breakdown, at a rate determined by its 5,600-year half-life. Therefore, any piece of preserved bone, any bit of charcoal from an ancient campfire, or organic remains of any kind could be dated by measuring the amount of radiocarbon left. The method is reasonably accurate for objects up to 30,000 years old, and this covers archaeological history from the ancient civilizations back to the beginnings of Cro-Magnon man. For developing this technique of archaeometry, Libby was awarded the Nobel Prize for chemistry in 1960.

  Cro-Magnon was not the first early man dug up by the archaeologists. In 1857, in the Neanderthal valley of the German Rhineland, a digger discovered part of a skull and some long bones that looked human in the main but only crudely human. The skull had a sharply sloping forehead and very heavy brow ridges. Some archaeologists maintained that they were the remains of a human being whose bones had been deformed by disease; but as the years passed, other such skeletons were found, and a detailed and consistent picture of Neanderthal man was developed. Neanderthal was a short, squat, stooping biped, the men averaging a little taller than five feet, the women somewhat shorter. The skull was roomy enough for a brain nearly as large as a modern human’s (figure 16.4). Anthropological artists picture the creature as barrel-chested, hairy, beetle-brewed, chinless, and brutish in expression—a picture originated by the French paleontologist Marcellin Boule, who was the first to describe a nearly complete Neanderthal skeleton in 1911. Actually, Neanderthal was probably n
ot as subhuman as pictured. Modern examination of the skeleton described by Boule show it to have belonged to a badly arthritic creature. A normal skeleton gives rise to a far more human image. In fact, give a Neanderthal man a shave and a haircut, dress him in well-fitted clothes, and he could probably walk down New York’s Fifth Avenue without getting much notice.

  Traces of Neanderthal man were eventually found not only in Europe but also in northern Africa, in Russia and Siberia, in Palestine, and in Iraq. About a hundred different skeletons have now been located at some forty different sites, and human beings of thissort may still have been alive as recently as 30,000 years ago. Skeletal remains somewhat resembling Neanderthal man were discovered in still more widely separated places; these were Rhodesian man, dug up in northern Rhodesia (now Zambia) in southern Africa in 1921, and Solo man, found on the banks of the Solo River in Java in 1931. They were considered separate species of the genus Homo, and so the three types were named Homo neanderthalensis, Homo rhodesiensis, and Homo solensis. But some anthropologists and evolutionists maintain that all three should be placed in the same species as Homo sapiens, as varieties or subspecies of man. There were humans that we call sapiens living at the same time as Neanderthal, and intermediate forms have been found which suggest that there may have been interbreeding between them. If Neanderthal and his cousins can be classed as sapiens, then our species is perhaps 250,000 years old.

  HOMINIDS

  Darwin’s Origin of Species launched a great hunt for our distinctly subhuman ancestors—what the popular press came to call the missing link between us and our presumably apelike forerunners. This hunt, in the very nature of things, could not be an easy one. Primates are quite intelligent, and few allow themselves to be trapped in situations that lead to fossilization. It has been estimated that the chance of finding a primate skeleton by random search is only one in a quadrillion.