It was an extremely unlikely fluke that we developed radios at all, and more of a fluke that we developed them before we developed the technology that will end us in a slow stew or fast bang. While Earth's history thus offers little hope that radio civilizations exist elsewhere, it also suggests that any that might exist are short-lived.
We are very lucky that that is so. I find it mind-boggling that the astronomers now eager to spend a hundred million dollars on the search for extraterrestrial life have never thought seriously about the most obvious question: what would happen if we found it, or if it found us. The astronomers tacitly assume that we and the little green monsters would welcome each other and settle down to fascinating conversations. Here again, our own experience on Earth offers useful guidance. We have already discovered two species that are very intelligent but technically less advanced than us—the common chimpanzee and pygmy chimpanzee. Has eur response been to sit down and try to communicate with them? Of course not. Instead we shoot them, stuff them, dissect them, cut off their hands for trophies, put them on exhibit in cages, inject them with AIDS virus as a medical experiment, and destroy or take over their habitat. That response was predictable, because human explorers who discovered technically less advanced humans also regularly responded by shooting them, decimating their populations with new diseases, and destroying or taking over their habitat. Any advanced extraterrestrials who discovered us would surely treat us in the same way. Think again of those astronomers who beamed radio signals into space from Arecibo, describing Earth's location and its inhabitants. In its suicidal folly that act rivalled the folly of the last Inca emperor, Atahuallpa, who described to his gold-crazy Spanish captors the wealth of his capital and provided them with guides for the journey. If there really are any radio civilizations within listening distance of us, then for heaven's sake let's turn off our own transmitters and try to escape detection, or we are doomed.
Fortunately for us, the silence from outer space is deafening. Yes, out there are billions of galaxies with billions of stars. Out there must be some transmitters as well, but not many, and they do not last long. Probably there are no others in our galaxy, and surely none within hundreds of light-years of us. What woodpeckers teach us about flying saucers is that we are unlikely ever to see one. For practical purposes, we are unique and alone in a crowded universe. Thank God!
PART FOUR
WORLD CONQUERORS
Part three discussed some of our cultural hallmarks and their animal precedents or precursors. Several of those hallmarks are ones that we are proud of, though one (agriculture) has proved to be a mixed blessing and another (chemical abuse) an unmitigated evil. Those cultural hallmarks—especially language, agriculture, and advanced technology—have been the causes of our rise. They are what permitted us to expand over the globe and become world conquerors. That expansion, though, consisted of more than our conquering areas previously unoccupied by the human species. It also involved the expansion of particular human populations that conquered, expelled, or killed other populations. We became conquerors of each other, as well as of the world. Thus, our expansion has been marked by yet another human hallmark that has animal precursors and that we have taken far beyond its animal limits—namely, our propensity to kill other members of our species en masse. Along with our environmental destructiveness, it now poses one of the two potential causes for our fall.
To appreciate our rise to the status of world conquerors, recall that most animal species are distributed over only a small part of the Earth's surface. For example, Hamilton's frog is confined to one forest patch of thirty-seven acres plus one rock-pile covering 720 square yards in New Zealand. The most widespread wild land mammal other than humans used to be the lion, which as of 10,000 years ago occupied most of Africa, much of Eurasia, North America and northern South America. Even at the time of its greatest extent, though, the lion did not reach Southeast Asia, Australia, southern South America, the polar regions, or islands. There are even more widespread bird species that occur on all continents except Antarctica, such as the barn owl or peregrine falcon, but they too are absent from many islands, high elevations, cold climates, and all the oceans.
Humans used to have a typically mammalian restricted distribution, in warm, non-forested areas of Africa. As recently as 50,000 years ago, we were still confined to tropical and mild-temperature areas of Africa and Eurasia. Then we expanded in turn to Australia and New Guinea (around 50,000 years ago), cold parts of Europe (by 30,000 years ago), Siberia (by 20,000 years ago), North and South America (around 11,000 years ago), and Polynesia (between 3,600 and 1,000 years ago). One dramatic stage in this expansion of ours into a large realm formerly without people—the New World—will be the subject of a later chapter, Chapter Eighteen. Today we occupy or at least visit not only all lands but also the surface of all the oceans, and we are starting to probe into space and the oceans' abysses.
In the process of this world conquest, our species underwent a basic change in the relations between its populations. Most animal species with sufficiently wide geographic ranges fall into populations that have contact with neighbouring populations but have little or no contact with distant ones. In this respect, too, humans used to bejust another species of big mammal. Until relatively recently, most people spent their entire lives within a few dozen miles of their birthplace, and had no way of learning even of the existence of people living at much greater distances. Relations between neighbouring tribes were marked by an uneasy shifting balance between trade and xenophobic hostility.
This fragmentation promoted, and was reinforced by, the tendency for each human population to develop its own language and culture. Initially, the massive expansion of our species' geographic range involved a massive increase in our linguistic and cultural diversity. Among the 'new' parts of our range occupied only within the last 50,000 years, New Guinea and North and South America alone came to account for about half of the modern world's languages. Much of that long heritage of cultural diversity has been erased in the last 5,000 years by the expansion of centralized political states. Freedom of travel—a modern invention—is now accelerating that homogenization of our language and culture. However, in a few areas of the world, notably New Guinea, stone-age technology and our traditional xenophobic outlook persisted into the Twentieth Century, giving us a last glimpse of what the rest of the world used to be like. Chapter Thirteen will try to convey some feeling for our pre-homogenized condition, and for what we have lost as well as gained through our new-found mobility.
The outcome of conflicts between expanding human groups has been heavily influenced by group differences in our cultural hallmarks. Especially decisive have been differences in military and maritime technology, in political organization, and in agriculture. Groups with more advanced agriculture thereby acquired the military advantage of larger population numbers, ability to support a permanent military caste, and resistance to infectious diseases against which sparser populations had evolved no defence.
All those cultural differences used to be ascribed to genetic superiority of conquering 'advanced' peoples over conquered 'primitive' ones.
However, no evidence of such genetic superiority has been forthcoming. The likelihood of genetics playing such a role is refuted by the ease with which the most dissimilar human groups have mastered each other's cultural techniques, given adequate learning opportunities. New Guineans born of stone-age parents now pilot aeroplanes, while Amundsen and his Norwegian crew mastered Eskimo dog-sledding methods to reach the South Pole. Instead, one has to ask why some people acquired the cultural advantages that let them conquer other people, despite lack of any evident genetic advantages. For example, was it purely by chance that Bantu peoples originating from equatorial Africa displaced Khoisan people over most of southern Africa, rather than vice versa? While we cannot expect to identify ultimate environmental factors behind small-scale conquests, chance should play less of a role and ultimate factors should be more compelling if we focus on large-scale population shifts over long times. Hence Chapters Fourteen and Fifteen will examine two of the largest-scale shifts in recent history: the modern expansion of Europeans over the New World and Australia; and the perennial puzzle of how Indo-European languages managed earlier to overrun so much of Eurasia from an initially restricted homeland. We shall see clearly in the former case, and more speculatively in the latter, how each human society's culture and competitive position have been shaped by its biological and geographical heritage, especially by the plant and animal species available to it for domestication.