More recently, my own modern human ancestors mated with Neanderthals, evolved the ability to digest milk as adults and developed pinkish skin. Pale skin enabled my female predecessors to produce sufficient vitamin D to support the growth of their children during pregnancy and to lactate in the dark northern winters. The European population was gradually growing apart from the ancestral Ethiopian population from which we originated. The differences that we see between human populations that live outside Africa have arisen within the last 60,000 to 100,000 years–or 2,500 to 4,000 generations (1–2 per cent of the separation between us and chimps)–as a result of new genetic mutations, natural selection which favours some of these mutations over others, continued migration and some degree of hybridization with other types of human who already inhabited the Eurasian continent. The usual natural evolutionary processes were taking place. There is a possibility that, perhaps a million years from now, we might have ended up with many different human species spread across the world, just as a population of an earlier Homo evolved into a distinctive dwarf species on the Indonesian island of Flores, where it survived until its extermination (perhaps by Homo sapiens) about fifty thousand years ago. This separation into many different human species could have been our destiny, had it not been for the torrent of human movement around the world that we have seen in recent times, the consequence of which is that the world’s human genes are ending up back in one big Pangean melting pot. Humanity is setting off on a new evolutionary journey.
A young orangutan in Sabah, Borneo. Both humans and orangutans have evolved naturally in the half a million generations since we shared the same parents, hence the impacts of humans and orangutans on other species are natural.
There is absolute scientific certainty that we evolved from apes (we still are apes), that we are still evolving and that the evolution of humans was a perfectly natural event in the history of life on Earth. We were then able to overcome most diseases that would otherwise limit our population, engineer the environment so that we could survive across most of the land surface, and commandeer more and more of the world’s resources, as well as bring down mammoths and the rest of the great beasts that we drove to extinction. Extensive agricultural landscapes and the architecture and cities that Oscar Wilde approved of exist because humans evolved, and hence permitted the success of sparrows, Oxford ragwort and the other species that live in them. Entirely natural. The new distributions of species we have transported across the world are equally natural. All these things represent an indirect product of evolution.
The very fact that we continue to conceptualize a separation between humanity and nature over a century and half after Darwin and Wallace developed their ‘dangerous idea’ implies that there must be something quite fundamental driving the sense of ‘other’ whenever a human contemplates nature. And the most fundamental thing about us is that we evolved. Evolution by natural selection brought us into existence in the first place, and it is evolution that has also made it difficult for us to accept that we are simply a part of the natural world. Evolution has programmed us, by means of a complex system of biochemical, electrical and genetic mechanisms, to love and protect our offspring, mates and wider family, because their safety and subsequent reproduction is the primary means by which our genes are transmitted to the next generation.8 That love is real to us, but there is an evolutionary reason why it exists. We also co-operate with and learn from other humans who are members of our tribe, whether it be in our local community, sports team, school, workplace, profession, age group, religion or nation, in order that we might survive, prosper and, ultimately, pass on our genes; and this evolved and cultural tribalism is retained even in individuals who opt not to reproduce. We also fight social, economic and physical wars with other members of the human species to protect what each of us perceives to be the collective good. Other humans are critically important to every one of us, hence it is a simple consequence of evolution that you and I respond more strongly to humans than to other animals and plants; we are predisposed to treat humans as separate from the rest of nature. Members of our own species represent our potential mates, offspring, collaborators and enemies. But this sense of being separate and special is not unique to humans. African lions, American bison and killer whales respond strongly to other members of their own species for exactly the same reasons. Members of their own species represent potential mates, offspring, collaborators and enemies. Every species is special to itself because the survival of each individual’s genes depend on it.
This presents us with intellectual conflicts between our rational, instinctive and cultural understandings of the world. Our rational assessment concludes that the natural principles of physics and chemistry generated an increasingly complex set of ‘evolved’, self-perpetuating chemical reactions, which we call biological life, with no ultimate purpose or intended future. Humans are part of that. Our instinctive or evolved logic, which is then usually reinforced by our culture, is geared to ensure that we propagate our own chemistry by keeping safe, defending ourselves, reproducing successfully, protecting our offspring and relatives, assisting those who might in turn assist us and bartering with those who have something of value to us. Most of the time, this internal or instinctive logic dominates our thinking and behaviour because it is what brought about our existence. No surprise, therefore, that most present-day humans still distinguish between humans and the rest of nature.
Our evolutionary predisposition towards ourselves and other people makes it far easier for us to develop philosophies in which humans are (somewhat) separate from nature than it is for us to recognize the truth: that we evolved completely naturally, we are still animals, and everything that we do to the rest of the world is natural. We may not be happy about some of the changes that are taking place as a consequence of our existence, but they are still natural.
Not only did we evolve naturally, but it is self-evident that the laws of physics, chemistry and biology were not revoked when humans turned up–we are simply using them to our own ends. Think of some of the changes which might lead people to conclude that our impacts are unnatural. Yes, we drove many of the largest land animals to extinction, but this is not new. Many large animals became extinct when North and South America came into contact with one another, long before humans were around. In fact, mass extinction events over the last half-billion years typically extinguished the largest species. These human-caused extinctions are simply a consequence of us acting as an ecological predator.
Next comes transport. Humans have accelerated the rate at which the seeds of plants and animals are moved around the world in recent times, but we did not invent long-distance travel. Building aeroplanes is completely novel, but flying is not; we are just the first animal to develop a physical tool to do so (unless one counts small caterpillars and spiders that suspend themselves from threads of silk and are transported by the wind). Flying birds moved seeds, mites and diseases 50 million years ago, long before we were a twinkle in the eye of our proto-ape ancestors. Similarly, ships and vehicles have hugely increased the rates at which species are moving between different parts of the world, but we did not invent swimming; remember that tortoises made it to the Galapagos Islands, presumably by hanging on to floating vegetation. On land, the movement of plant seeds was once mediated by herds of elephants but is now achieved by humans and their vehicles, and by the horticultural trade. Why is transport by one mammal (elephant) more natural than transport by another (human)? Humans are simply acting as dispersal agents for other animals and plants–a completely natural process.
The consequence of humans changing the climate is that species are gradually shifting their geographic ranges towards the poles and to higher altitudes. Again, this is not new. On each of the many previous occasions when the climate has changed (for both physical and biological reasons), the world’s species moved. Lastly, we come to transforming the land. Dinosaurs were quite effective at transforming habitats before giant rhinoceros and then eleph
ants came on the scene, only to be deposed by humans, who are now the main agents of disturbance. When humans harvest fields of wheat and corn, it is not fundamentally different from the activities of leaf-cutter ants. These amazing insects collect leaves and grow fungal crops in underground nests, then harvest the nutrient-rich growths of the fungi to feed their developing grubs. When we drink cow’s milk, it is comparable to other ants that drink the nutritious and sugary exudates of blackfly herds, which they tend like miniature shepherds. When we build huts, houses and dams, it is no different to beavers doing the same. When we use new genetic technologies to move genes from one species into another, it is an extension of the transfer of genes that has previously been accomplished by hybridization, and by microbial and viral parasites. We have just taken these same things to new levels. Of course, many of the specific materials we use are new, and the complexity of our tools and communication systems are without parallel, but we have not invented entirely new biological processes. Even if we achieve this in the future, it will still be a consequence of our prior natural evolution.
The upshot of all these quantitative (but not qualitative) changes is a new natural world order in which all manner of populations and species are living in locations they did not previously inhabit. Novel biological communities have come into existence, from the dust mites that live in our beds to the microbes and pelagic invertebrates that attach themselves to fragments of plastic, which float across the world’s oceans. An enormous diversity of plants, invertebrates and even vertebrates are living and evolving in cities,9 and we have planted entirely new forests for wood. European plants are now growing across vast swathes of North and South America, thanks to us moving them there, and they cannot be repatriated. Moths deep in the protected jungle of Sabah’s sacred Mount Kinabalu have moved upwards as humans have warmed the climate, and remote reefs are changing where they face higher temperatures and the increasing acidity of the sea. Forest trees growing in the depths of the Amazon jungle have experienced the loss of the largest mammals that used to eat them, growth-altering increases in the levels of carbon dioxide in the atmosphere and physiologically vital changes to the climate. The footprint of human impact is ubiquitous, yet the natural processes of ecology and evolution are still operating in every case. From a biological perspective, individuals are still born and die, populations grow and decline, and evolution takes place. These are regular, natural processes. Why would we regard these new, human-altered ecosystems as any less natural than the ecological and evolutionary processes that are still operating within them?
The world is one in which the specific combination of species and genes in any one place is new but the fundamental biological processes that are in operation are the same as before. While I am describing the current state of the world in this sentence, I emphasize it because I could describe any past period of environmental change with identical words. It would be equally apt for each of the twenty or so great swings in the world climate that have taken place during the last million years. In other words, we can describe human and non-human impacts in exactly the same terms. Species have always moved and evolved, and they have done so particularly rapidly whenever the environment has changed, whatever the cause.
Accepting that ecological and evolutionary change is how nature works means that we must contemplate life as a never-ending sequence of events, not as a single fixed image of how it looks today. This dynamic perspective of life on Earth allows us to put aside most of our doom-laden rhetoric and recognize that the changes we see around us, including those that have been directly or indirectly engineered by people, are not necessarily fundamentally better or worse than the ones that went before. They are just different. We can enjoy and make use of species wherever they might now live, appreciate new Anthropocene species that are coming into existence, and only try to fix things that we, as humans, really think need fixing. We do not need to fix things simply because they are different.
In any event, there is no point crying over spilt milk. The human and non-human contributions to every ecosystem are already inseparable. The practical reality is that the only places where we can attempt to protect the world’s ‘natural’ species from further losses are in bits of the world that have already been altered by humans. Even if we were to remove every human from the surface of the planet today, it would not revert to what it once was.
Standing on the flat roof atop a sixteen-storey former apartment block, the tingling fear of heights set in. I approached the unguarded edge, a high vantage point over the former Ukrainian town of Pripyat, gazing over a post-human world. Swifts, descendants of feathered dinosaurs, wheeled through the air, nesting in crevices in the abandoned buildings. The tops of hotels, schools, a hospital and a Ferris wheel peeked out above the forested landscape, remnants of a utopian Soviet world. Beyond, a brand-new, gleaming steel-and-concrete sarcophagus sat poised, ready to seal in the radiation from Chernobyl Nuclear Reactor Number 4. Like latter-day Mayan temples that became entombed by forest when European diseases initiated the collapse of an extensive former civilization in Central America, Pripyat is a lesson in how ephemeral the impact of humanity can be.
Thirty years after the terrible nuclear disaster that befell Chernobyl on 26 April 1986, Pripyat is a ‘lost city’ in the making. It is a land from which people have been removed. Visiting troops of tourists appear from time to time to gawp at the shells of buildings from which the valuables have been stolen, and to take emotive photographs of children’s possessions that have been callously arranged for this purpose. Then there are security personnel and thousands of workers who still toil in radiation-limited shifts to decommission and encase the former nuclear reactors. Apart from that, a handful of elderly peasant farmers have returned to smallholdings to live out the remainder of their lives. It is not completely unpopulated, but it is close. There are also some radiation hotspots, particularly just downwind of the original disaster, but these quite localized areas are embedded in a far more extensive landscape: 2,600 square kilometres on the Ukrainian side of the border, and a further 2,165 square kilometres in Belarus. Geometry dictates that well over 90 per cent of the wildlife lives in places where radiation levels are tolerable and from where humans have moved out. This wider landscape is a window on to what would happen to the Earth if humans were to depart.
As I peered from the dizzying summit of the apartment cliff, the Trinidad-sized exclusion zone was punctuated by monumental relicts of humanity rising above a verdant sea of green. Just a few kilometres away from the failed reactor, falcons rear their chicks on ledges in a derelict cooling tower, their screeching calls echoing in the great, empty chamber. Enormous, slippery catfish gobble up the offerings tourists drop into the canal that was dug to pipe water from the cooling systems. Fishing prohibited, they can reach their full potential. Red-backed shrikes, with their hooked beak, rusty-coloured shoulders, grey head and black mask, fly down to catch grasshoppers, lizards and small rodents, and impale their prey on thorny shrubs. Successfully immobilized, these butcher birds then shred their victims into digestible lumps. Iridescent emperor butterflies jostle with gold-and-brown hornets for the sweet exudates from an oak tree which marks the entrance to an abandoned children’s nursery that has sunk beneath the emerald canopy of the entombing forest. The landscape has become home to substantial numbers of wild boar, moose, deer, bear and wolves,10 although they lie low during the heat of the day. Wild–albeit hybrid–European bison have been released. A black stork wheels overhead.
The former Ukrainian town of Pripyat, with the Chernobyl nuclear reactor and its new cover in the background. Nature is taking back the land, but the forest that is returning includes North American as well as European trees, and Asian raccoon dogs seek meals on the abandoned streets. When humans leave part of the world, it does not return to a pre-human state.
Thirty years after the event, the benefits of removing human activity from most parts of the landscape can be seen. To a casual observer, nature is ret
urning to how it ‘should be’.
Yet it is not reverting to a pre-human world. Erect horticultural cultivars of urban poplars now form dense stands around Pripyat. They push up through the former pavement and their saplings emerge from cracks in the concrete, half a dozen storeys from the ground. They are joined by invasive box elder, a kind of North American maple, that contributes to the regrowth. The inhabitants of the Soviet empire welcomed horticultural offerings from their foes, it seems. The suckers of American locust trees form thorny groves in former municipal gardens and render sports fields invisible. The reversion to forest is being hastened by an array of foreign as well as European plants. Raccoon dogs from eastern Asia prowl beneath these North American trees. In the absence of the extinct European tarpan, conservationists have released endangered Przewalski’s wild horses into this weird landscape, despite the fact that these animals come from the grasslands and semi-deserts of central Asia. Extinct forest elephants and giant beavers that would once have helped to maintain openings in the forest, which would have suited the horses, have not existed for a long time. They are not available to return.
Take humans away, and what do we see? The atmosphere and climate have been altered and cannot be buffered from the rest of the world. The land is not reverting to a pre-human version of pristine. Introduced animals and plants from distant continents are here to stay, and will evolve into European versions of their American and Asian relatives.11 These are permanent biological gains, while large mammals that we extinguished in the distant past are permanent losses. This is unnatural, some might say, yet all the species that are thriving in this landscape are perfectly natural species. The practical reality is that the future of the Earth has already been permanently altered because humans have existed. We cannot unpick it all now.
Inheritors of the Earth Page 22