The Great Divide

much between the two hemispheres. Part Three is a narrative, two narratives in fact, entwined around each other, as we follow the different trajectories as people in the two hemispheres both evolved great – but in some ways very different – civilisations.
    Broadly speaking, The Great Divide seeks to show that the physical world which early people inhabited – the landscape, the vegetation, the non-human animal life, plus the dominant features of the climate, of latitude and the relation of the land to the sea – determined the ideology of humans, their beliefs, their religious practices, their social structure, their commercial and industrial activities, and that, in turn, ideology, once it had emerged and cohered, determined the further characteristic interaction between humans and the environment. It may be true, as the socio-biologists and geneticists say, that there is only one human nature. But the very different environments across the world created some very different ideas that early peoples had about human nature. And, as this book seeks to show, that was in many ways more important.
    Our story will show that each hemisphere depended on, and was determined by, three very different phenomena. Vast stretches of the Old World fell under the influence of the Asian monsoon, the seasonal rainy period that extended from the eastern Mediterranean to China, which supported two-thirds of the world’s farmers and which has, for reasons we shall explore, been gradually weakening in strength for the past 8,000 years. This meant that fertility was the main preoccupation of religion in the Old World. Second, the existence of domesticated mammals exerted another all-important influence over the course of ancient history in the Old World, in particular the nature and extent of inter-societal competition and warfare. In the New World in contrast, the dominant influences were extreme – violent – weather, and, third, the much wider availability, variety and greater abundance of hallucinogenic plants. Together, these factors meant that religion, ideology, took on a far more vivid, intense and apocalyptic tone in the Americas.
    The Great Divide attempts quite an ambitious synthesis of what, to begin with, may appear to be very different disciplines: cosmology and climatology, geology and palaeontology, mythology and botany, archaeology and volcanology.
    It also makes use of one of the great breakthroughs in modern scholarship that has occurred since the Second World War – namely, the understanding of the newly deciphered scripts of the four main Mesoamerican civilisations – the Aztec, Mixtec, Zapotec and Mayan. Although only four Mayan books escaped the Spanish flames during the Conquest, other books or codices, produced jointly by Spanish clerics and Native Americans, and now countless inscriptions on stone stelae, altars and flights of stone steps, and other monuments and sculptures, are understood to such effect that the last thirty years have seen a massive explosion in knowledge and understanding of pre-Columbian life in the New World.
    The Great Divide uses this recent scholarship to formulate a systematic comparison between ancient history in the two hemispheres, and in doing so we shall see that there were very different trajectories as between Eurasia and the Americas. Despite these different paths, both hemispheres developed similar features, but it is the di ff erences that are our concern here, in this book. They tell us just as much about human nature – and maybe more – as the similarities do.
    In examining these trajectories jointly, we shall not only see what happened – when and where the civilisations began to diverge – but why .

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F ROM A FRICA TO A LASKA: T HE G REAT J OURNEY AS R EVEALED IN THE G ENES , L ANGUAGE AND THE S TONES
    I f our ‘experiment’ of
     comparing developments in the New World with those in the Old is to have as much meaning
     as possible, then we need to be as clear in our minds as we can be as to what extent the
     people in the two hemispheres were similar in the beginning. Or, failing that, we need
     to know how they differed. Clearly, this is not an easy task – we are talking of
     a time of at least 15,000 years ago and, in much of the material in this and the next
     chapter, a lot longer ago than that. But, although the time depth is daunting, and the
     material of such a nature that we need to be cautious at all times – since so
     much is