Extinction: Evolution and the End of Man

Table of Contents

Cover Page

Title Page

Introduction

1 The Past Is Not Over

2 Extinction

3 A System out of Chaos

4 From Dinosaurs to Us

5 What’s in a Name?

6 A Man-Made Extinction Event

7 Humans and the Future

Notes

Index

Acknowledgements

About the Author

Copyright

About the Publisher

Introduction

An e-mail message showed up on the screen when I logged on after breakfast. For my taste, boiled fish and rice with chopsticks don’t make the best start to the day, but the message more than made up for that. It was manna from heaven, like scrambled egg and smoked salmon, a taste of something good in this unfamiliar country.

The message was from one of my students in London, Dilshat Hewzulla. He’s a computer scientist from north-west China, a whiz kid at taking a complex system from one domain and computing it into something recognisable in another. I give him huge databases from extinct and living plants and animals, as well as from the environment, and he finds mathematically significant patterns for evolutionary and environmental interpretations. It may sound simple but it isn’t. In his e-mail Dilshat explained that in my absence we had received a letter from The Royal Society publications office saying that our manuscript had been accepted by the editor. Apparently two of the referees had waxed lyrical about it and the other had said it was rubbish and shouldn’t see the light of day. But our arguments had won through. My research group had finally gained the recognition of others and was seen to be on to something that would interest the rest of the scientific community.

With an excited feeling of satisfaction, I went off for a cup of tea. That, at least, they do have in Taiwan. I was in the capital, Taipei, at the Academy of Sciences, as the UK delegate to the General Assembly of the International Union of Biological Sciences. The tearoom was not crowded. Across the room my friend from the United States waved me to join his little group of three. They were talking about the major topic of the meeting: the effect of man changing the environment.

The day before, the Assembly had charged two of the scientists seated around that table with the task of finding ways of monitoring these changes upon the world around us. There had been hints from some delegates that without a clear programme of measurements their governments wouldn’t take the United Nations Biodiversity Convention seriously. ‘How can a forum like this agree on what to measure?’ asked one. ‘The diversity of life and environment is so big and complex, it’s hard to know where to start, and most species are not even described.’ ‘How can we bring marine and terrestrial ecologists together, whose different domains influence one another very strongly?’ ‘Do meteorologists ever speak to biologists or those modelling sea-level changes?’ Not only are there these scientific problems but also the political ones, as well as financial issues. ‘The developing world will never cooperate as long as the West carries on using so much fossil fuel,’ said the Indian delegate, ‘and even you developed nations can’t raise the money to educate people about biodiversity, let alone monitor the changes in environments.’

Later, the Assembly did agree on some priority locations. They designated areas around the world where individual animals and plants are to be identified and counted, the rainfall and temperature logged and the soil types classified. But there are so many other variables to monitoring these possible changes, and they are all affected in different ways at different rates. The scale of time to be monitored was another factor to include in the survey: changes overnight; throughout the year; a decade; a millennium; a few million years. Though my two friends are leading specialists in mainstream biology and ecology, on their own they didn’t have a clue how to begin to advise their Ministries. Theirs was an intractable dilemma. We know so little about the losses of species and ecosystems over the last hundred years, yet we all have a strong gut feeling that we are wrecking life on our planet. For governments, neither the questions nor the answers will win many votes.

But they are questions we must not shirk just because of their intractable complexity. They are not for experts in any one discipline, such as my friends in the tearoom, but for the person who can connect all the many disciplines involved. My attempt to contribute some kind of answer to this dilemma is the narrative of this book, and Dilshat’s e-mail message signalled the first attempt at a new approach. Our Royal Society paper brought together data from biology, ecology and geology and analysed them mathematically. The data come from changes that have been taking place through tens, hundreds, thousands and millions of years, and the patterns of biological diversity that emerge through evolutionary changes help understand many of the problems raised in the Taipei tearoom. The patterns our study revealed are journeys through time. The journey includes extinctions, origins and diversifications of species and larger groups. The biology matches changes that can be seen in environments, drawing the two different subjects closer together. These connections not only have an exquisite beauty when enshrined on Keats’s Grecian urn but also they are seen to have changed through the scales of geological time: ‘“Beauty is truth, truth beauty”/ – that is all ye know on earth, and all ye need to know.’

This is the story of evolution on our planet from the time of one set of extinctions to another, which covers the last 65 million years and reaches into the future. As well as clues from fossils the plot has evidence from every witness we can find – modern plants and animals, rocks, chemicals, atoms and other sources. The information and ideas come from most of the natural and physical sciences and beyond. We bring together as many of these natural processes of environment and biology as we can, as well as evidence from many hitherto separate disciplines.

I used to call myself a paleontologist because I studied fossils. My research thesis work in the 1960s looked into thousands of broken-up bits of trees that turned out to be 6 million years old. They came from a clay pit in the middle of England, a collapsed cave in the limestone hills of Derbyshire, and they showed that a warm redwood forest had once grown there. It was not unlike parts of California today but with an English scale to the landscape. So much has changed in such a geologically short period of time, yet the Peak District really did look like Sequoia National Park in California, the dense mixed forest of deciduous English oak and elm mixed with trees now native only in North America, as well as others found mainly in the East, making rich soils and colourful hills. Where there was bad soil and good drainage, heathland was much like that today; where there was wetland different but familiar plants and animals prospered.

This was a few million years before the glaciers of the ice ages penetrated into the presently highly populated temperate regions of the Earth where most of the large cities of the developed world are now situated. Before the glaciers spread from the poles, warm temperate forests dominated humid hilly landscapes. Shrubs and heath covered the drier soils and grass became widespread for the first time, encouraged by vast increases in the numbers of stooping grazing mammals. The atmosphere had more CO2 than now, which meant it was much warmer. The polar icecaps were much smaller than now, but growing. If you had taken an aeroplane journey with the usual flight paths from Europe to California, or over Siberia to Beijing, you would have seen the same kinds of forest on both trips: redwoods and warm temperate forest on the hills, swamp cypresses and shrubs near the water, like the kind you see now in the Florida Everglades. They were mixed in with more of the kinds of trees and shrubs you see in the southern United States and warm temperate China – oaks, maples, pines. Further north, a flight from Heathrow to Vancouver would cross the cooler landscape of familiar birch forest with pine and alder: there was much less sea than now, and no ice.

Over the last forty years specialists from different parts of the natural sciences have come together to paint pictures of how the world looked millions of years ago. Their reconstructions are opening up new issues about climate change, plant migration, evolution, ecology and the statistics of populations. Now that we are taking these previously separate disciplines together, we can begin to see how they affect the urgent new environmental issues facing our modern world. My own studies have strayed into many other different methodologies, genetics, geology, ecology, taxonomy and even statistics. So now I call myself an evolutionary biologist rather than the paleontologist that I once was.

Since those exploratory days of the 1960s the scientific literature has been filled with detail about these biological and environmental changes. As the first half of the twentieth century was for theoretical and descriptive biology, so the second half accumulated large amounts of data about the evolutionary relationships between species and the environment. A climax was reached in 1977 when Fred Sanger learnt how to sequence the gene leading to genetic engineering. Two decades later DNA sequencing is being done automatically. Now the results create huge new databases each day, like new rows of books on shelves a kilometre long. Environmental ecologists and taxonomists are part of this new age of very large data recovery, and are beginning to seek automatic techniques to find, store and analyse the data. But there’s so much becoming available that it’s hard to manage at an international level.

One of the achievements of my research group at the University of East London is that we can analyse large databases interactively across the internet. This means we are able to assemble ideas and information from different sources, from which we can begin to see life on our planet as a complex system. Maybe we can understand how it survives and changes as a whole, for only then can the problems raised around the Taipei tea table be understood and tackled. We are just beginning to make a start to link the bits together.

Throughout my career I have been privileged to see many more of these bits from the whole of science than most people. At University College London during the early 1960s my degree course included lectures by Francis Crick and Sydney Brenner just when they were cracking the triplet genetic code. This was also when J. B. S. Haldane, the pioneer of an earlier revolution in genetics, was to be seen walking through the North Cloisters with a pillow stuffed up his jumper to comfort his cancer. The mathematics of mutation and the recombinations in dominant and recessive gene characters were the centre of his kind of biology: it is hardly heard of today. From this cusp between the old and the new I wandered with chemistry and geology, got stuck in thermodynamics, and touched on the philosophy of science. The more adventurous natural scientists were looking outwards from the strict demarcations of individual disciplines. J. Z. Young was busy changing the way anatomists think and Peter Medawar was breaking thoughts about immunology and the way science works. Karl Popper was down the road and the Beatles slept on the floor next door in my student residence.

All these different perceptions of life were being assembled together in the same place at the same time, squeezing out traditions from separate backgrounds into one amorphous shape. At least it seemed to be amorphous then, hard to put into any clear context or application. They were years of joy for the fearless intellectuals of science. Now, just forty years on, the shape has a much clearer identity, itself being replaced by a fresh wave of integration with new objectivity. Studies of organismal biology had peaked by the 1960s. The principles of structure and function which gave names to ‘genes’ suddenly led into the language of the triplet code in molecular genetics.

I was helped by my tutor, Bill Chaloner, a luminary in paleontology with a gift for communicating the fascinations of evolutionary processes. Those critical studies led into more defined ideas on how landscapes and ecologies change through different timescalcs. We were fired by the enthusiasms of the new wave to link all these traditions by looking at an issue from several different perspectives. They were exciting times because you could feel attitudes changing. That’s happening again, now, at the beginning of the new century. But this time the changes are going to be very big indeed and are beginning to affect our lives.

These experiences have influenced me to give a broad mind to an argument, often at the risk of being called ‘ecumenical’. In retrospect I see that’s how I reacted to the many factors relevant to environmental and evolutionary biology, genetics, geology, ecology and mathematics. They are all working together, constituting a complex system on our planet that can be traced back to the extinction of the dinosaurs and beyond. For most of the incidents that are thought to have changed that system there are a number of opposing theories. For example, to explain the sudden demise of so many large groups of animals 65 million years ago, there are at least four different ideas. First, a meteorite hit the Earth causing a 20km crater just off the Mexican coast and worldwide fires that killed big animals. Second, there was severe volcanic activity in India. Third, there were continuing physiological difficulties controlling body temperature. Finally, all the food ran out and the dinosaurs starved to death.

The different theories are a good example of how science works, with argument and limited facts to test the more fanciful solutions being offered. What holds good as an answer today is more than likely to be different from what was understood yesterday, and it will differ again tomorrow. But trends and patterns do emerge, and we are beginning to see things more clearly with more data from different disciplines. The growth of computing power and the introduction of the internet have been vital factors in making these leaps in understanding possible.

On the other hand, these are frightening times. On New Year’s Day 2000 the World Wildlife Fund and the Guardian newspaper published a booklet entitled A New Century a New Resolution. In it, the then chief scientific adviser to the UK government, Sir Robert May, issued a warning about ‘our greatest challenge’. In his view, this was to ‘ensure that any increase in global productivity is achieved in a sustainable and environmentally friendly way. We really do live at a special time in the history of Life on Earth. A time when human activities have come to rival the scale and scope of the natural processes which built, and which maintain, the biosphere.’ If we take action now, he argued, we can avert a catastrophe.

I take a more pessimistic view. In this book I present evidence to show that that catastrophe has been well under way for many thousands of years, and that Bob May’s observations of what we are doing to the environment now amount to just a final nail in the coffin. Most people think of time only in terms of their own lifelong experience of it, or a few hundred years more, at best. But if you extend your thoughts of time back further, past the last millennium into the first, and think of what the world might have been like, things look quite different from today. Now compare our present world with what it looked like before humans started to interfere, a few thousand years ago, and there are more changes still. The evidence of what early human hunters did to other large mammals shows enormous horror, resulting in the extinction of a number of species. It has all happened since the end of the last full glaciation, 10,000 years ago. That’s a period of time few of us are ever asked to consider. So when I’m asked to say how long it will be before the forthcoming extinctions, I say: ‘Soon, but remember, I’m a paleontologist.’

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