Free The Rational Optimist by Matt Ridley

near Taforalt in Morocco, where forty-seven perforated shells, some smeared with red ochre, date from certainly more than 82,000 years ago and perhaps as much as 120,000 years ago. Similar shells, harder to date, have been found at Oued Djebanna in Algeria and Skhul in Israel, and perforated shells of the same genus but a different species are found at Blombos cave in South Africa from about 72,000 years ago along with the earliest bone awls. These shells were surely beads, probably worn on a string. Not only do they hint at a very modern attitude to personal ornament, symbolism or perhaps even money; they also speak eloquently of trade. Taforalt is 25 miles and Oued Djebanna 125 miles from the nearest coast. The beads probably travelled hand to hand by exchange. Likewise, there are hints from east Africa and Ethiopia that the volcanic glass known as obsidian may have begun to move over long distances around this time too, or even earlier, presumably by trade, but the dates and sources are still uncertain.
    Just across the strait of Gibraltar from where these bead-wearing, flake-making people lived were the ancestors of Neanderthals, whose brains were just as big but who showed no signs of making beads or flake tools, let alone doing long-distance trade. There was clearly something different about the Africans. Over the next few tens of millennia there were sporadic improvements, but no great explosion. There may have been a collapse of human populations. The African continent was plagued by ‘megadroughts’ at this time, during which desiccating winds blew the dust of extensive deserts into Lake Malawi, whose level dropped 600 metres. Only well after 80,000 years ago, so genetic evidence attests, does something big start to happen again. This time the evidence comes from genomes, not artefacts. According to DNA scripture, it was then that one quite small group of people began to populate the entire African continent, starting either in East or South Africa and spreading north and rather more slowly west. Their genes, marked by the L3 mitochondrial type, suddenly expanded and displaced most others in Africa, except the ancestors of the Khoisan and pygmy people. Yet even now there was no hint of what was to come, no clue that this was anything but another evolutionary avatar of a precariously successful predatory ape. The new African form, with its fancy tools, ochre paint and shell-bead ornaments, might have displaced its neighbours, but it would now settle down to enjoy its million years in the sun before gracefully giving way to something new. This time, however, some of the L3 people promptly spilled out of Africa and exploded into global dominion. The rest, as they say, is history.
    Starting to barter

    Anthropologists advance two theories to explain the appearance in Africa of these new technologies and people. The first is that it was driven by climate. The volatility of the African weather, sucking human beings into deserts in wet decades and pushing them out again in dry ones, would have placed a premium on adaptability, which in turn selected for new capabilities. The trouble with this theory is first that climate had been volatile for a very long time without producing a technologically adept ape, and second that it applies to lots of other African species too: if human beings, why not elephants and hyenas? There is no evidence from the whole of the rest of biology that desperate survival during unpredictable weather selects intelligence or cultural flexibility. Rather the reverse: living in large social groups on a plentiful diet both encourages and allows brain growth.
    The second theory is that a fortuitous genetic mutation triggered a change in human behaviour by subtly altering the way human brains were built. This made people fully capable of imagination, planning, or some other higher function for the first time, which in turn gave them the capacity to make better tools and devise better ways of making a