Henry Gee Pan Macmillan (UK: Available now US: 18 March)
We’re doomed, says Henry Gee, doomed! Homo sapiens is reaching a crest, after which our global population size will start to drop. In his new book, The Decline and Fall of the Human Empire: Why our species is on the edge of extinction, Gee’s mission is to trace the path from our genesis to our peak, then on to our quite possible annihilation.
When H. sapiens evolved about 300,000 years ago, we were surrounded by relatives. At home, in Africa, we lived alongside H. naledi and H. heidelbergensis. In Europe, when we reached it, there were the Neanderthals; in Asia, the Denisovans.
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We may well have overlapped with other human species that are as yet unknown. While our sister species went extinct, not only did we flourish, we grew to dominate the entire planet. Why, asks Gee, did we, out of all the other human groups, do so well?
His answer is population size. Eventually, after several brushes with extinction ourselves, we started growing in number. Instead of ideas being lost, they stuck and were developed. Technology and culture exploded. When there are villages of several dozen people, cave painting becomes a possibility. When you have a civilisation of billions, flying to space becomes a probability. It’s why there is a gap of only 66 years between the Wright brothers’ first powered flight in 1903 and the moon landing in 1969.
So much for the boom – now for the bust. Gee uses Edward Gibbon’s classic work The History of the Decline and Fall of the Roman Empire as a framing device. Gibbon’s point is that once Rome had conquered all its enemies, the empire started to rot.
And so, too, with us, warns Gee. Once we had seen off all the other human species, the clock on our own extinction started ticking. It doesn’t help that the human population also passed through numerous bottlenecks (one seeing the population drop to some 1300 individuals nearly a million years ago) and that these stripped us of much of our genetic variation.
Elon Musk has said he wants to help make Homo sapiens into a multi-planet species
United Nations projections suggest that the world population will peak at just over 10.4 billion in 2086, then fall. One contributory factor, writes Gee, is the worldwide decline in sperm count over the past few decades, possibly due (among many things) to gradual exposure to the pollutants created by fossil fuels. Great. If Big Oil doesn’t wipe us out through climate change, it may help do so through effects on infertility.
Gee’s scholarship is impeccable and lightly worn. He was the winner of the Royal Society science book prize in 2022 for his A (Very) Short History of Life on Earth: 4.6 billion years in 12 chapters and has, for some decades, been an editor at the journal Nature.
The Decline and Fall of the Human Empire is hugely informative and entertaining – if your idea of entertainment is being constantly reminded of the precipice we are approaching as a species. But I can’t think of another author who could pull off Gee’s straight-talking, detached-yet-jovial style. He is such an amiable guide to our doom.
That tone changes in part three when Gee attempts a Hollywood-style happy ending, because, unlike the Romans, he says, we have the chance to escape. He argues that expanding off-planet in the next 100 to 200 years is our only chance of long-term survival as a species.
The late physicist and cosmologist Stephen Hawking claimed something similar in an episode of Tomorrow’s World in 2017, saying we had 100 years to find a new home, revised down from his earlier estimate of 1000 years. Elon Musk, too, has said he wants to help make H. sapiens a multi-planet species.
They may all be right. But as much as I enjoy the science fiction idea of colonising space, I feel that it opens the door to doomerism and defeatism. We have to put all our energy into transitioning to a sustainable world on this planet – and then we can look to expand.
Both outcomes are still possible: a sustainable future on this planet and expansion to other worlds. Gee shows how much of our success thus far has been down to luck, but we can’t rely on that to get us much further.
