Humans are altering the planet, including long-term global geologic processes, at an increasing rate. Any formal recognition of an Anthropocene epoch in the geological time scale hinges on whether humans have changed the Earth system sufficiently to produce a stratigraphic signature in sediments and ice that is distinct from that of the Holocene epoch.
Biologically, there is nothing remarkable in the fact that humans are agents of ecological change and environmental upset. All species transform their surroundings. The dizzying complexity of landscapes on Earth is not just a happy accident of geology and climate, but the result of billions of years of organisms grazing, excavating, defecating, and decomposing. Nor is it unusual that certain lucky species are able to outcompete and eventually entirely displace other species. The Great American Interchange, when North American fauna crossed the newly formed isthmus of Panama to conquer South America three million years ago is just one among countless examples of swift, large-scale extinctions resulting from competition and predation.
The driving human forces responsible for many of the anthropogenic signatures are a product of the three linked force multipliers: accelerated technological development, rapid growth of the human population, and increased consumption of resources. These have combined to result in increased use of metals and minerals, fossil fuels, and agricultural fertilizers and increased transformation of land and nearshore marine ecosystems for human use. The net effect has been a loss of natural biomes to agriculture, cities, roads, and other human constructs and the replacement of wild animals and plants by domesticated species to meet growing demands for food. This increase in consumption of natural resources is closely linked to the growth of the human population. Anatomically modern Homo sapiens emerged ~200,000 years ago . Around the start of the Holocene, humans had colonized all of the continents except Antarctica and the South Pacific islands and had reached a total population estimated at 2 million. Up to this point, human influence on the Earth system was small relative to what has happened since the mid-20th century; even so, human impacts contributed to the extinction of Pleistocene megafauna. However, the key signals used to recognize the start of the Holocene epoch were not directly influenced by human forcing, which is a major distinction from the proposed Anthropocene epoch.
What is remarkable, however, is the stunning speed of human adaptation relative to other species, and that our adaptation is self-directed. From sonar and flight to disease immunity, humans can ‘evolve’ exquisite new traits in a single generation. The Anthropocene represents a catastrophic mismatch between the pace of human technological evolution and the genetic evolution of nearly every other species on Earth. As with many other geological epochs, the Anthropocene has been heralded with a mass extinction, one which is generally accepted to be the sixth great one to occur on Earth.
The Anthropocene represents a catastrophic mismatch
Mass extinctions, however, have always been succeeded by a recovery of biodiversity. The Permian mass extinction made room for dinosaurs to flourish; the Cretaceous extinction gave rise to the marvellous diversification of mammals and birds. These massive adaptive radiation events, where surviving populations swiftly speciate, take anywhere from tens of thousands to tens of millions of years, depending on the degree of the initial extinction and the stability of the Earth’s climate.
Population extinctions today are orders of magnitude more frequent than species extinctions. Population extinctions, however, are a prelude to species extinctions, so Earth’s sixth mass extinction episode has proceeded further than most assume. The massive loss of populations is already damaging the services ecosystems provide to civilization. When considering this frightening assault on the foundations of human civilization, one must never forget that Earth’s capacity to support life, including human life, has been shaped by life itself . When public mention is made of the extinction crisis, it usually focuses on a few animal species (hundreds out of millions) known to have gone extinct, and projecting many more extinctions in the future. But a glance at our maps presents a much more realistic picture: they suggest that as much as 50% of the number of animal individuals that once shared Earth with us are already gone, as are billions of populations. Given the increasing trajectories of the drivers of extinction and their synergistic effects. Future losses easily may amount to a further rapid defaunation of the globe and comparable losses in the diversity of plants, including the local (and eventually global) defaunation-driven coextinction of plants. The likelihood of this rapid defaunation lies in the proximate causes of population extinctions: habitat conversion, climate disruption, overexploitation, toxification, species invasions, disease, and (potentially) large-scale war— all tied to one another in complex patterns and usually reinforcing each other’s impacts. Much less frequently mentioned are, however, the ultimate drivers of those immediate causes of biotic destruction, namely, human overpopulation and continued population growth, and overconsumption. These drivers, all of which trace to the fiction that perpetual growth can occur on a finite planet, are themselves increasing rapidly. Thus, to emphasize, the sixth mass extinction is already here and the window for effective action is very short, probably two or three decades at most. All signs point to ever more powerful assaults on biodiversity in the next two decades, painting a dismal picture of the future of life, including human life.
No matter the severity of the extinction, however, vacant ecological niches are eventually filled and new ones are created as life adapts to a newly empty Earth. Keeping this in mind, it’s possible to argue that not all human activity is antithetical to biodiversity. Our destructive tendencies might actually be a form of creative destruction, clearing the playing field so marginalized actors can dominate. More controversially, human activity may actually create new species and modes of being, just as the Cambrian explosion 530 million years ago was marked by biological breakthroughs such as active predation, hard exoskeletons, and the beginning of the vertebrate body plan.
Our destructive tendencies might be a form of creative destruction
What if we already are in the midst of a previously unnoticed adaptive radiation phase, an ‘Anthropocene explosion’, that has so far gone unnoticed? Where should we look for this evolutionary event? Three groups of entities are at the cusp of notable speciation events: human-associated animals, genetically engineered organisms, and manmade technologies, both physical and digital.
Firstly, the most obvious beneficiaries of the Anthropocene explosion are those that have been the sole actors in past adaptive radiations, that is, living organisms. Synanthropes—organisms that associate with human settlements—have adopted the human environment as their native habitat, and therefore likely have a bright future ahead of them. Our cultural evolution is mirrored in their genetic evolution. Pests and pathogens, for instance, evolve in concert with pesticides and medicines. Many city animals already show specific adaptations to the loud, hectic and artificially bright urban wilderness. As the Anthropocene marches onwards, the speculative naturalist may be tempted to hope that rats, cats and cockroaches will diversify into new and splendid forms. In the realm of ‘true’ wilderness, certain creatures are thriving as the human machine decimates others. In this area, the ocean is perhaps the starkest example. Scraped clean by long lines and bottom-trawlers, and acidified by a carbon-heavy atmosphere, the oceans face a ‘gelatinous future’ dominated by jellyfish and microbes, which will flourish in the ecological niches vacated by fish. Only the most nihilistic observer, however, would argue that an ocean dominated by jellyfish and microbes has the same value as one teeming with corals, sharks, and whales, or that a rat-and-trash filled alley is as ecologically productive or philosophically inspiring as a forested valley.
Human activity may create new species and modes of being
Although breeding domesticated species for selected traits speeds up genetic change, it will not gift the Anthropocene with fantastic new species. We’ve pushed the genetic envelope in terms of how much milk a cow can produce, or how small a chihuahua can shrink while still remaining a functioning organism. Despite their extravagant appearances, these animals are not distinct species from their wild counterparts. It will be thousands or even millions of years before truly novel species emerge from the diversification of synanthropes and other tenacious clingers-on.
It therefore secondly falls to genetic engineering to add truly novel organisms to the ‘Anthropocene Explosion’. The transgenic GlowFish, for instance, is one of the most well-known and appealing ‘charismatic microfauna’ of the GMO world, a creature which is in many ways as wonderful as the common zebrafish. The GlowFish is a first step towards creating a new, valid species. A creature even more marvellously engineered, perhaps even pieced together gene by gene to construct an organism from the ground up, would be equally valid and worthy of our appreciation and protection as a species that arose through natural selection.
Thirdly, we need to look at technology to see a potential for a new type of evolutionary event. There is something poetic in the fact that the widespread acceptance of the Anthropocene coincides with the moment that our technologies are poised to become as complex and autonomous as organic life. The sphere of human thought, culture, and technology—sometimes called the noosphere or the technium—is not just dependent upon the biosphere but intimately bound up with it, and vice versa. Though we have maintained a stubbornly mechanical conception of technology, in truth the technosphere may be, or be becoming, a valid form of nature, populated by actors that are ‘species’ in everything but name.
Does it falls to genetic engineering to add truly novel organisms to the ‘Anthropocene Explosion’?
Up until now, what has prevented humans from viewing individual technologies in more organismal terms are their predictability and simplicity. What we are beginning to see are the very early stages of man-made technologies that may one day become as richly complex as DNA-based organisms. If technologies should someday exhibit true autonomy, able to gather energy on their own, repair themselves, and reproduce, it would be difficult to argue in good faith that their existence is any less ‘natural’ than that of a grasshopper or anemone. A technological species does not need to mimic an organic one in order to be viable. In fact, a digital or genetically engineered copy of the original is bound to pale in comparison. Rather than creating artificial sentience that matches that of an animal or human, it may be far more interesting to foster new, unprecedented forms of mind and embodiment.
Do we need to look at technology to see a potential for a new type of evolutionary event?
However, individuals of any species in isolation cannot exactly be said to constitute a nature. ‘Nature’ is a highly complex, unpredictable assemblage composed of interacting individuals. No matter how majestic a reminder of the wilderness, a polar bear in a zoo is more a cultural artefact than an aspect of nature; no matter how much it reminds us of a living dog, the Big Dog robot is still more cultural than natural.
Though humans often wrongfully categorize the natural world through the lens of technology—the body is a machine, a forest is a factory—there is a strong resonance between the digital and the genetic. An organism’s ‘hardware’ is encoded in the software of DNA and RNA. Life, in all its apparent glory, exists solely for the propagation of genetic information. Our bodies are elaborate (and disposable) vehicles for our genomes, which have been upgrading from body to body, species to species over the last four billion years.
From this perspective, all of nature is merely the interaction of billions of genetic programs. If this is true, then interacting man-made digital technologies might be the equivalents of physical ecosystems. It’s therefore arguable that the sum total of earth’s information flow has not diminished during the Anthropocene, but rather that biodiversity has merely switched media from nucleotides to electronic circuits. It may be that one day we be able of perfectly simulating entire ecosystems, from an entire redwood down to the last neuron in a snail’s brain, and that we could run this simulation many times over. Human technology, then, could be responsible for many more manifestations of ‘nature’ than the previous Earth was ever capable of sustaining.
But … is this what we want?