Читать книгу The Rational Optimist: How Prosperity Evolves - Matt Ridley, Matt Ridley - Страница 19

He steps under the shower, a forceful cascade pumped down from the third floor. When this civilisation falls, when the Romans, whoever they are this time round, have finally left and the new dark ages begin, this will be one of the first luxuries to go. The old folk crouching by their peat fires will tell their disbelieving grandchildren of standing naked mid-winter under jet streams of hot clean water, of lozenges of scented soaps and of viscous amber and vermilion liquids they rubbed into their hair to make it glossy and more voluminous than it really was, and of thick white towels as big as togas, waiting on warming racks.

IAN MCEWAN

Saturday

One day a little less than 500,000 years ago, near what is now the village of Boxgrove in southern England, six or seven two-legged creatures sat down around the carcass of a wild horse they had just killed, probably with wooden spears. Each took up a block of flint and began to fashion it into a hand axe, skilfully using hammers of stone, bone or antler to chip off flakes until all that remained was a symmetrical, sharp-edged, teardrop-shaped object in size and thickness somewhere between an i-phone and a computer mouse. The debris they left that day is still there, leaving eerie shadows of their own legs as they sat and worked. You can tell that they were right-handed. Notice: each person made his own tools.

The hand axes they made to butcher that horse are fine examples of ‘Acheulean bifaces’. They are thin, symmetrical and razor-sharp along the edge, ideal for slicing through thick hide, severing the ligaments of joints and scraping meat from bones. The Acheulean biface is the stereotype of the Stone Age tool, the iconic flattened teardrop of the Palaeolithic. Because the species that made it has long been extinct we may never quite know how it was used. But one thing we do know. The creatures that made this thing were very content with it. By the time of the Boxgrove horse butchers, their ancestors had been making it to roughly the same design – hand-sized, sharp, double-sided, rounded – for about a million years. Their descendants would continue to make it for hundreds of thousands more years. That’s the same technology for more than a thousand millennia, ten thousand centuries, thirty thousand generations – an almost unimaginable length of time.

Not only that; they made roughly the same tools in south and north Africa and everywhere in between. They took the design with them to the Near East and to the far north-west of Europe (though not to East Asia) and still it did not change. A million years across three continents making the same one tool. During those million years their brains grew in size by about one-third. Here’s the startling thing. The bodies and brains of the creatures that made Acheulean hand axes changed faster than their tools.

To us, this is an absurd state of affairs. How could people have been so unimaginative, so slavish, as to make the same technology for so long? How could there have been so little innovation, regional variation, progress, or even regress?

Actually, this is not quite true, but the detailed truth reinforces the problem rather than resolves it. There is a single twitch of progress in biface hand-axe history: around 600,000 years ago, the design suddenly becomes a little more symmetrical. This coincides with the appearance of a new species of hominid which replaces its ancestor throughout Eurasia and Africa. Called Homo heidelbergensis, this creature has a much bigger brain, possibly 25 per cent bigger than late Homo erectus. Its brain was almost as big as a modern person’s. Yet not only did it go on making hand axes and very little else; the hand-axe design sank back into stagnation for another half a million years. We are used to thinking that technology and innovation go together, yet here is strong evidence that when human beings became tool makers, they did not experience anything remotely resembling cultural progress. They just did what they did very well. They did not change.

Bizarre as this may sound, in evolutionary terms it is quite normal. Most species do not change their habits during their few million years on earth or alter their lifestyle much in different parts of their range. Natural selection is a conservative force. It spends more of its time keeping species the same than changing them. Only towards the edge of its range, on an isolated island, or in a remote valley or on a lonely hill top, does natural selection occasionally cause part of a species to morph into something different. That different sport sometimes then spreads to conquer a broader ecological empire, perhaps even returning to replace the ancestral species – to topple the dynasty from which it sprang. There is constant ferment of change within the species’ genes as it adapts to its parasites and they to it. But there is little progressive alteration of the organism. Evolutionary change happens largely by the replacement of species by daughter species, not by the changing of habits in species. What is surprising about the human story is not the mind-bogglingly tedious stasis of the Acheulean hand axe, but that the stasis came to an end.

The Boxgrove hominids of 500,000 years ago (who were members of Homo heidelbergensis) had their ecological niche. They had a way of getting food and shelter in their preferred habitat, of seducing mates and rearing babies. They walked on two feet, had huge brains, made spears and hand axes, taught each other traditions, perhaps spoke or signalled to each other grammatically, almost certainly lit fires and cooked their food, and undoubtedly killed big animals. If the sun shone, the herds of game were plentiful, the spears were sharp and diseases kept at bay, they may have sometimes thrived and populated new land. At other times, when food was scarce, the local population just died out. They could not change their ways much; it was not in their natures. Once they had spread all across Africa and Eurasia, their populations never really grew. On average death rates matched birth rates. Starvation, hyenas, exposure, fights and accidents claimed most of their lives before they were elderly enough to get chronically ill. Crucially, they did not expand or shift their niche. They remained trapped within it. Nobody woke up one day and said ‘I’m going to make my living a different way.’

Think of it this way. You don’t expect to get better and better at walking in each successive generation – or breathing, or laughing, or chewing. For Palaeolithic hominids, hand-axe making was like walking, something you grew good at through practice and never thought about again. It was almost a bodily function. It was no doubt passed on partly by imitation and learning, but unlike modern cultural traditions it showed little regional and local variation. It was part of what Richard Dawkins called ‘the extended phenotype’ of the erectus hominid species, the external expression of its genes. It was instinct, as inherent to the human behavioural repertoire as a certain design of nest is to a certain species of bird. A song thrush lines its nest with mud, a European robin lines its nest with hair and a chaffinch lines its nest with feathers – they always have and they always will. It’s innate for them to do so. Making a teardrop-shaped sharp-edged stone tool takes no more skill than making a bird’s nest and was probably just as instinctive: it was a natural expression of human development.

Indeed, the analogy with a bodily function is quite appropriate. There is now little doubt that hominids spent much of those million and a half years eating a lot of fresh meat. Some time after two million years ago, ape-men had become more carnivorous. With their feeble teeth and with finger nails where they should have had claws, they needed sharp tools to cut the skins of their kills. Because of their sharp tools they could tackle even the pachydermatous rhinos and elephants. Biface axes were like external canine teeth. The rich meat diet also enabled erectus hominids to grow a larger brain, an organ that burns energy at nine times the rate of the rest of the body. Meat enabled them to cut down on the huge gut that their ancestors had found necessary to digest raw vegetation and raw meat, and thus to grow a bigger brain instead. Fire and cooking in turn then released the brain to grow bigger still by making food more digestible with an even smaller gut – once cooked, starch gelatinises and protein denatures, releasing far more calories for less input of energy. As a result, whereas other primates have guts weighing four times their brains, the human brain weighs more than the human intestine. Cooking enabled hominids to trade gut size for brain size.

Erectus hominids, in other words, had almost everything we might call human: two legs, two hands, a big brain, opposable thumbs, fire, cooking, tools, technology, cooperation, long childhoods, kindly demeanour. And yet there was no sign of cultural take-off, little progress in technology, little expansion of range or niche.