How are we to view extinction? The loss of species caused by human negligence is terrible, and yet extinction happens naturally as part of the regular turnover of species through the long spans of geological time. There is much to be learnt from those natural extinctions.
As a child, when I was introduced to dinosaurs and fossils, I loved the fact they were extinct. I could imagine these past worlds of trilobites, great bone-armoured fishes, ichthyosaurs, dinosaurs and mammoths. I dreamt then as I looked at my dinosaur books, that someday I could dig up these fossils and bring them back to life, not literally, but by using all the smart tools in the scientific laboratory to work out whether a particular dinosaur was warm-blooded or not, whether a giant pterosaur could fly and how a 50-tonne sauropod could find enough food to keep its huge body functioning successfully.
Extinctions happen on different scales. Single species extinctions have happened ever since life first evolved because each species only lasts for 1 to 10 million years before it evolves into something new or dies out. Larger than these are extinction events when many species die out at the same time because of a regional crisis. Mass extinctions were largest of all, times when thousands of species died out at the same time everywhere. There were five mass extinctions, the last of which happened 66 million years ago, at the end of the Cretaceous Period, when the dinosaurs disappeared.
If we weep over the death of the dodo, should we also lament the millions of species that died out through the history of life? In fact, mass extinctions can have a creative aspect. What is often seen in the recovery from devastation is something completely new. This is what happened when the mammals took off after the extinction of dinosaurs. The mammals had been held back, ecologically speaking, by the dinosaurs and could only freely diversify after the dinosaurs had been removed from the scene.
Other examples of such evolutionary innovation include the consequences of the mass extinctions at the end of the Permian and in the Triassic. These triggered the evolution of modern-style ecosystems in the sea and on land – we trace such modern phenomena as coral reefs, fast-swimming fishes, modern sharks and molluscs in the oceans, as well as flies and beetles, modern conifer trees, frogs, lizards, crocodiles and mammals on land, back to the opportunities for new evolution that had been generated by those mass extinctions.
Is extinction good or bad? We must certainly regret that we killed the dodo and will never get to see this lovely bird. Its place on the island of Mauritius is empty and nothing has replaced it, so in the balance of nature, there is a place for the dodo. Is the answer, then, to bring extinct species back to life? This is a popular idea that we saw in the Jurassic Park movies and in travellers’ tales of exquisitely frozen mammoth carcasses, so perfect you could even eat the flesh. However, the DNA from dinosaurs has long gone, and the technology to somehow breathe life back into frozen mammoth flesh is not there. Genetic engineering can allow scientists to modify the genes of modern elephants to give them mammoth-like qualities, like an ability to survive in colder climates.
But, is there room in modern ecosystems for mammoths? Humans have squeezed the space for wild nature so much in the past two hundred years that there isn’t enough room for the ten million species on Earth today, let alone reintroducing extinct species as well. Is it always a tragedy when a species becomes extinct? I am argue a rather opposite view in this book. Palaeontology shows us that many billions of species that once existed are now extinct, and their natural extinctions enabled new species to inherit the Earth. But this case is certainly not in favour of humans causing the extinction of any species, merely a reminder that extinction is a natural part of evolution and requires deeper thought.