The descent of man

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by Chris Stringer and Peter Andrews
Thames and Hudson £24.95, 240 pages

SURVIVING ARMAGEDDON: Solutions for a Threatened Planet
by Bill McGuire
OUP £14.99, 248 pages

Think backwards, think forwards, and above all think big. These two books bring together much of the current debate on where humans came from, how the world looked at them at different times, the nature of the societies they have created and where they are now going. It is not all cheerful reading.

First there is a useful reminder about how new the human species is. Chris Stringer and Peter Andrews use the time-honoured device of comparing the history of life on Earth to events in a year. If the Earth began on January 1, it was not until February or March that the first bacteria-like creatures appeared, and not until 20 minutes to midnight on December 31 that the first modern humans appeared, and our familiar time reckoner, the Christian era, began at 15 seconds to midnight. We are by no means at the end of the story.

Certainly we have not had much time to exercise the role that some would like to ascribe to us: stewards of the Earth. What is certain is that in the past few years we have been making an unholy mess of it, with more mess to come. How did this happen?

Stringer and Andrews go back to the beginning of human evolution, with lively and imaginative illustrations throughout. Their book contains a careful analysis of the tools that can be used to assess the evidence, together with case histories from different parts of the world. Points of controversy are not avoided, for example over the lines of descent from the long past, which look more like a bush with many twigs than a single family tree.

The timing - or timings - of the dispersal of humans from their origin in Africa remains in dispute. There are those who believe in the so-called multi-regional model, whereby through interbreeding over the last million years different descendants of Homo erectus have given rise to modern humans; and those - now the majority - who see our evolution through Homo heidelbergensis from a more recent African group to include the famous mitochondrial Eve. Our Neanderthal cousins were still living some 30,000 years ago, and the miniature humans whose bones were discovered recently on the Indonesian island of Flores, with marked Homo erectus characteristics, were apparently living only 18,000 years ago.

With this rich and complex genealogy, it is hard to be precise about what constitutes a modern human. At one time it was believed to lie in our use of tools. But birds use tools too; chimpanzees even make them. Language is also a tricky criterion. Many animals communicate through sounds and gestures. Chimpanzees lack our speaking mechanism, but through keyboards and symbols can learn up to 200 “words” and arrange them in sequences. But language and symbolism as we use them are unknown in any other animal, and are part of a system of behaviour which, with fuzziness at the edges, can be characterised as unique.

When are the first traces of modern humans seen? Whereas the first human use of tools can be dated to more than two million years ago, the first clear forms of art in Africa go back 75,000 years, and the amazing cave paintings at Chauvet have been dated at approximately 30,000 years ago. Why did the change take place? Was it gradual, responding to natural selection favouring big brains? But Neanderthals had big brains too. Was there some critical genetic mutation which still brings an occasional interesting mix of high intelligence and schizophrenia? How is it that we are the only species of Homo left? Few species last for ever, and with loss of variety perhaps we are ill adapted to cope with the kind of challenges, environmental and other, that will certainly come in the future.

Stringer and Andrews end their book where Bill McGuire begins his, and with the same sense of apprehension, even alarm. They refer to the current multiplication of human numbers, over-exploitation of resources, the possibilities of nuclear war, and the hazards created by human-driven climate change. For his part McGuire starts his analysis of the threats now facing the planet with the natural disasters that from time to time have disrupted the Earth’s ecosystem.

The biggest and most obvious are hits from space of the kind that ended the long dominance of the dinosaur family. More relevant to people living today was the earthquake that led to the tsunami of December 26 2004 and an estimated quarter of a million deaths. Among possibilities for the future, there is the prospect of a sudden collapse of part of the Cumbre Vieja volcano in the Canary Islands. This could cause a tsunami that would race over the Atlantic and swamp the Caribbean and the east coast of the US, carrying death and destruction with it. Asteroid hits, earthquakes and volcanic eruptions are part of Earth’s history, and there is little we can do about them except take evasive action if and when we can foresee them.

Climate change is another matter. McGuire takes us through a familiar analysis of the effects of the steep increase in human-generated greenhouse gases in the atmosphere. Rapid changes in patterns of rainfall and drought, cold and warmth, and all that goes with them - such as water distribution, fertility of soils, and the other forms of life on which we depend - could cause havoc to the over-stretched human society we have today. In the past, humans could and did move or adapt to such changes, but in our present and growing numbers, it is hard to imagine anything but increasing disruption.

We can still limit greenhouse gas emissions if we decide to do so. Yet some, notably in the US, are in a state of denial. They are so trapped in the conventional wisdom of growth economics, with vested interests in support, that they remain blind and deaf to what is going on around them.

There is an occasional bleat to the effect that technology will find an answer. The evidence, well examined by McGuire, is powerfully against this. Certainly technology can help, but it can also create as many problems as it solves.

As Martin Rees has pointed out in another context, technology has problems of its own. He rates the chances of our civilisation surviving this century at no more than 50 per cent.

The approach in these books is very different. The Complete World of Human Evolution is a scholarly and well-written series of essays on how we arrived where we are. Surviving Armageddon is a somewhat boisterous romp through the thickets of our possible futures. Inevitably there is more about Armageddon than survival, and some of the solutions suggested are far from practical. If there is optimism about human ability to cope, there is pessimism about the human will to do so, above all in good time. Read both books. And then have a strong drink.

Sir Crispin Tickell is chancellor of the University of Kent

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