Extinction: Evolution and the End of Man. Michael Boulter
cheap in North America; Europe consumes timber from dwindling tropical rainforest. The tourist industry booms globally. So we go on living through a catastrophe of a kind that our planet has never experienced. It has suffered major environmental changes before, with a consequent loss in biodiversity, but never have they been caused by a selfish species.
Within a few tens of thousands of years we have progressed from scenes of ice age glaciers to temperate interglacials, no doubt causing the extinction of many mammal species. Then there were aggressive hunts by humans for more mammals in Africa, Europe and Asia, and eventually America. Now we humans direct our aggression to abusing our environment. The importance of this sequence of man-made crises becomes clear when you realise that all these human actions have lasted only a few thousands of years, a quick flash in the 400 million years through which our planet has had life on land.
On the other hand, you can argue that these few thousand years are a long time in comparison to the two hundred or so years since the Industrial Revolution. What we’ve done in our short sojourn on Earth may be comparable to other catastrophic events that happened millions of years ago. It’s 65 million years since the last big catastrophe. It happened in a flash. It took seconds for the meteorite to pass through the Earth’s atmosphere before the impact explosion and then the long environmental recovery.
Of course, what’s happening now is different. The damage we are inflicting has been taking place since the end of the last ice age, about 10,000 years ago, and we are doing it in stages. The most recent stage is dominated by burning oil. Relatively recently, in April 1899, the New York Herald Tribune wrote: ‘Two motor cars will commence to carry Her Majesty’s mails in London itself, the postal authorities having decided to give the new means of locomotion a fair trial. They have quite as great a carrying capacity as the two-horse vans.’ Before this, we burnt another fossil fuel, coal, in quantity from the start of industrialisation. Going back further, wood was the main fuel, bringing about large-scale deforestation, and the whole catastrophe began just a little earlier when we hunted so many mammals to extinction. Ten thousand years seems an age by the scale of a human lifetime, but geologically it is only a flash.
Journey from the beginning of time
To understand how this flash fits into geological time, it helps to take a virtual journey on a time machine in which one complete day represents the 65 million years that have passed since the last great environmental catastrophe when the dinosaurs became extinct – a journey in which today’s universe is not yet seven months old. Let’s go to the beginning of time, the Big Bang. Imagine it happening just after midnight on New Year’s Day. Within a fraction of that second, from infinite density, the universe begins. Time begins.
It’s intolerably hot and the thick atmosphere makes it difficult to see much. By 18 March of our virtual year the universe has reached 5,000 million years of age. There’s not a lot we know about what was happening then – exploding stars, balls of hot gases, no familiar planets to the suns. It’s getting cooler, or rather, it’s not so horribly hot. By 1 1 June one of the chunks of matter orbiting our sun breaks into three. Mars and the Earth are formed, and about 500 million years later, on 19 June, our moon. The temperatures gradually fall and by early July life begins on the Earth. (Some say it came from outer space, others that the necessary organic molecules lormed from the planet’s own inorganic chemistry.) There is no land cool enough for life until around 10 August, so until then early life is aquatic, often with a vast range of, to us, weird forms. Stephen Gould’s Wonderful Life describes some of these from the Burgess Shale, which Derek Briggs and scientists from the Smithsonian Institution have brilliantly described and illustrated.
Large numbers of these 54o-million-year-old fossils from British Columbia show that an enormous structural diversity was present early in the history of life. Because they are among the first non-microscopic organisms they have many unusual features, hard to find in fossils that lived since, and controversy continues to haunt our interpretations. The remains were discovered in 1909 by the paleontologist Charles Walcott, who explained them as ‘a sublime conception of God which is furnished by science.’ Their different shapes and structures show unusual variety, and many scientists have thought them to be unlike more recent animals that they have seen then representing extinct groups. They also seem to have diversified suddenly and become extinct just as quickly. A more recent approach has been to look at the similarities between the fossils’ characters. Links have been made to familiar groups like trilobites and sponges. The confusions should be no surprise, because most new things start off by looking strange.
Our 65-million-years-to-a-day journey is reaching familiar territory now. Through middle August life is evolving very fast, diversifying day by day – vertebrates, ferns, dinosaurs. Some groups become extinct in those early and mid-August days: trilobites and jawless vertebrates. Then, on 20 August, the dinosaurs become extinct as well. On this time scale, that happened yesterday.
On the chime of midnight for the start of this new day, 2 1 August, we wake from one of the planet’s most horrific nightmares. The northern hemisphere is completely blacked out with smoke and dust in the first milliseconds of our virtual day. The vegetation returns to normal after a few minutes, with only a few changes, while the oceans take longer to clear up the debris that has rained down from the dirty clouds. It has mixed into the sea, and robbed it of much oxygen, causing extensive extinctions of plankton and fish.
At an hour past midnight the noxious outfall from the nightmare has completely cleared and a bright new world is beginning to take advantage of the new opportunities. It is not unlike the upturn of the Western economies after the Second World War – hesitation to reacclimatise at the beginning, then a surge in diversification to reach new highs. This is a pattern I return to in chapter 5. Throughout this Paleocene period of geological time, up to about 3 am, the environment is establishing new ecological niches in the very warm climates. This allows the number of mammal species to peak by the 6 o’clock dawn, comfortable in the new reality that they arc no longer the prey of dinosaurs.
A very clear trend is developing which we will see characterising this whole last day of our journey. There are many new species ranked together in new large groups of genera and Families, but there are very few extinctions. Overall, there is a massive increase in biodiversity. In the early morning there are the first primates, the first horses, the first whales, whole new major groups of animals, each with hundreds of new species.
At 9 o’clock in the morning it is 49 million years ago, during the period of geological time we call the Eocene (see figure 1.2). The planet is becoming quite a familiar place, with dense mixed woodlands and savanna grazed by herds, and there are even cocks crowing. Monkeys are one of the big new groups to originate and quickly diversify. Global temperature differences are much less than today’s, the tropics being about the same and the poles equably temperate. The shores of the Arctic Ocean, as well as the hills of the Antarctic continent, have warm tranquil climes with low sun in the long summer and little if any frost in the darkness of the long winter. If there had been humans and a travel industry then, it would have been a tourist’s paradise for half the year.
Just before lunchtime, 35 million years ago on the geological timescale, temperatures have peaked due to high carbon dioxide concentrations in the atmosphere. The greenhouse effect in these times is much stronger than now. Continental drift causes the North Atlantic to widen and at about the same time to open into the then temperate Arctic Ocean. Temperatures at the poles begin to fall. We’re not sure how this happened but perhaps it was caused by some astronomical phenomenon, or by the changing positions of the continents and oceans.
In the nowadays highly populated northern temperate regions of the world, tropical rainforest stretches from Asia, eastwards to Europe and the newly separated continent of North America. The very rich faunas and floras begin to take on a familiar look. The world is becoming more varied, with more species than ever before, and its ecology more diverse, with a wide variety of modern habitats. With the wider-ranging weather and climate, and the peak diversification of animals and plants, come maximum complexity and range.
By now it’s early afternoon and many familiar groups of animals and plants are making their first appearance. While only the odd species