‘Once upon a time…’ The opening words of Henry Gee’s new book give notice that what follows will be a story – and a dazzling, beguiling story it is, told at an exhilarating pace. The scale is apparent from the first of a set of mind-boggling timeline graphics: this runs from the birth of the universe to ‘Extinction of life on Earth’, alarmingly close to the dotted line indicating ‘NOW’. This is a book to give you a dizzying perspective on such small matters as human civilisation. ‘Against the backdrop of geological time,’ Gee reminds us, ‘the sudden rise of humanity is of negligible significance.’ We’ll be gone in a while, leaving barely a trace behind. The carbon spike we have contributed to, and which causes us so much anxiety, is high, but on a graph showing trends over millennia it will be very narrow, ‘perhaps too narrow to be detectable in the very long term’. Besides, taking the long view, ‘life on Earth, with all its drama, all its comings and goings, is governed by just two things. One of them is a slow decline in the amount of carbon dioxide in the atmosphere. The other is the steady increase in the brightness of the Sun.’
Unlike carbon dioxide, oxygen might be thought of as an all-round good thing, essential to life on Earth. And yet it was a sudden surge of free oxygen that caused the Great Oxidation Event, unleashing the first of many mass extinctions that pepper the history of this planet. All that oxygen scrubbed the air of the carbon dioxide and methane that were keeping Earth warm and launched the first and longest ice age, 300 million years during which the planet became ‘Snowball Earth’, covered from pole to pole with ice. ‘And yet,’ observes Gee calmly, ‘the Great Oxidation Event and subsequent “Snowball Earth” episode were the kinds of apocalyptic disasters in which life on Earth has always thrived.’
Ice ages only encouraged life to keep coming back, sometimes in decidedly strange forms. I must admit I had never heard of the Lystrosaurus, an animal with ‘the body of a pig, the uncompromising attitude towards food of a golden retriever, and the head of an electric can opener’ – and yet, for millions of years after the End-Permian mass extinction (yes, another one), nine out of every ten animals on Earth was a Lystrosaurus. Nor had I heard of stromatolites, mounds of slime and sediment that developed early in the history of life on Earth, becoming ‘the most successful and enduring form of life ever to have existed on this planet, the undisputed rulers of the world for three billion years’.
Dinosaurs, meanwhile, are animals that every child has heard of. These hugely successful creatures filled every evolutionary niche, leaving little room for much else, including the early mammals; it wasn’t until the dinosaurs died out that mammals could ‘burst forth like a well-aged champagne, shaken beforehand, and inexpertly corked’. A profusion of fast-evolving and diversifying mammals took over from the dinosaurs. They included what Gee calls ‘a group of leftovers … an assortment of scrappers that included rats, mice, rabbits, and, seemingly almost as an afterthought, the primates’. These small, swift creatures with forward-facing eyes, inclined to curiosity and exploration, would eventually give rise to Homo sapiens. But the emergence of modern humans could so easily not have happened. Around 200,000 years ago, the last survivors of the species were confined to an oasis on the edge of what is now the Kalahari desert. Yet Homo sapiens squeaked through, saved by a period of warming that turned much of the surface of the planet into rich grassland, teeming with game.
Gee begins the last chapter of this hugely enjoyable page-turner by modifying a line from Tolstoy: ‘All happy, thriving species are the same. Each species facing extinction does so in its own way.’ This chapter contemplates the future – a future that will, of course, not include Homo sapiens. We have already incurred a massive ‘extinction debt’ by damaging our own habitat; our population is likely to start falling by around 2100; our genetic variation is woefully insufficient. We’ll be gone within the next ‘few thousand to tens of thousands of years’, but life will go on, with more ice ages and more extinctions, until eventually, in maybe a billion years, the story of life on Earth will be over.
Viewed from the kind of wide-angle perspective that Gee opens up, our human presence looks vanishingly insignificant. And yet we have huge significance as the first and only species to be aware of itself. We owe it to ourselves, and to our fellow species, to conserve what we have and to make the best of our brief existence.