Life made the modern Earth as much as the Earth made life, a new book by a philosopher of consciousness argues.
That dynamic leaves humans with a unique set of moral questions, Peter Godfrey-Smith of the University of Sydney writes in “Living on Earth: Forests, Corals, Consciousness, and the Making of the World,” a new book out this month.
“How would we behave if we took on board that we are part of the tree of life — but one with unusual powers?” Godfrey-Smith told The Hill.
Human activity has reshaped every aspect of natural life on Earth — from clearing land to acidifying the oceans and filling the air with planet-heating, plant-boosting carbon dioxide. But that change, Godfrey-Smith argues, isn’t a break with the history of life on earth.
Instead, he contends, the human activities reshaping the earth — destructive as they may be — are part of a much older story of how choices made by organisms, and often by intelligent organisms, have remade the Earth’s lands and waters in the image of life.
“Human action continues and extends a long tradition of organisms transforming nature, and the history of Earth includes a sequence of different forms of such reconstruction,” he writes.
“Living on Earth” begins with a set-piece: Godfrey-Smith returning from a diving trip in Western Australia’s Shark Bay, in a fossil-fuel burning car passing through the rust red landscape.
That scene, he writes, offers a micro-history of life on earth. The oxygen in the air that allowed the car’s fuel to burn was the product of the population explosion of oxygen-excreting cyanobacteria more than two-billion years ago, which also stained the rocks red; the fuel in the tanks was “made from compressed plankton and other marine organisms, settling in still water and then buried many millions of years ago.”
That oxygen burped out by ancient cyanobacteria — which made a world too toxic for them to dominate any longer — in turn powered the rise of fast, active animals. In conquering the land, with its long sightlines and difficult terrain, Godfrey-Smith writes that those animals gained access to a new world of both action and choice.
“On land, a more intense energy flux evolves in the blazing light, along with a tangle of coevolution between plants and new animals,” he writes.
“And then, in our own evolutionary line, an initially unremarkable mammal starts to change in new ways, forming societies and technologies.”
This change, he writes, led humans to kick off a stunning and sudden acceleration in the rate of change in the earth’s systems over the past century: a compression of geologic-scale change into human scale time.
That initially-unremarkable mammal’s actions led “eventually to change in the atmosphere itself, as carbon that was buried and transformed to oil is deliberately burned with life-derived oxygen to push our car along the highway north,” he writes.
As Godfrey-Smith hikes and swims across the landscape of Australia over the course of the book, he finds patterns like this wherever he goes. The present oil age — and life on earth in any recognizable sense — is possible because the cyanobacteria, ancestors of today’s plants, learned to use their own bodies to trap the vast fluxes of solar energy that constantly bombard the earth and hold them in the form of chemicals like sugar and starch, he notes.
Through this process “the Earth became infused, crammed, with energy in a way that would not happen without life,” he writes. That growing carpet of life has also reshaped the very landscapes: the roots of plants stabilize the sides of rivers, allowing them to form fast, defined channels that eat up and remake mountains and canyons.
Plants’ roots and the fungi that interweave with them also speed up the processes by which rocks weather, or bind carbon dioxide from the atmosphere — carbon that then runs off through those well-defined tributaries and down into the sea, cooling the atmosphere and serving as the ingredients for marine animals to make their shells, or for coral reefs to form.
Those shells and reefs are now dissolving as human burning of fossil fuels reverses this process — driving carbon dioxide into the oceans, where it dissolves those very shells.
But humans’ ability to do that is itself an outgrowth of their own natural history, Godfrey-Smith argues.
Humans, in his account, are special not because of their intelligence or sentience — these, he argues, are relatively common among animals — but because of several chance turnings in their long evolution.
Humans come, for instance, from the lineage of animals that left the oceans, which gave them both their four-limbed bodies — universal to all vertebrates on Earth — but also the possibility of harnessing fire, which is notoriously difficult underwater.
The human hands and fingers evolved to help earlier primates pick their way through tree canopies and were well suited to other forms of manipulation as the forests retreated.
Then, exiled to the spreading plains, hungry for meat and surrounded by dangerous predators, humans learned to live communally and to hunt cooperatively for success and survival.
This cooperation, to Godfrey-Smith, is perhaps the most remarkable aspect of human beings, and one that is distinct from even their closest relatives, the chimpanzees.
He quotes primatologist Sarah Hirdy, who has a thought experiment about what would happen if hundreds of unrelated chimpanzees were stuffed into, say, a Boeing 737: “Any one of [them] would be lucky to disembark with all ten fingers and toes still attached.”
Among octopuses, Godfrey-Smith notes, results would be even more chaotic: confined cephalopods often eat each other or their own limbs. And yet about 3 million humans are in the skies above the U.S. every day, and amputations and cannibalism are virtually unheard of.
This cooperation has, on the whole, been bad news for the other species with which humans have shared the planet, Godfrey-Smith noted.
“We’ve wiped out a lot of animal life, and most remaining biomass other than invertebrates and fish is under our control,” he said, “and most of what is under our control is treated cruelly.”
He singles out factory farming in particular as “a kind of abomination,” and raises the possibility that humans “shouldn’t use their powers to give other animals lives that aren’t worth living.”
But overall, Godfrey-Smith told The Hill that this sort of moral case is beyond the scope of the book.
Instead, he told The Hill, his principal point is that humans face the question of “What have we done with our kin — how have we treated them?”
That question has relevance for discussions of policy, rewilding, factory farming, animal experiments, climate change — but does not provide an easy answer for what should be done in any of those areas.
Instead, Godfrey-Smith said, the book is “an attempt to think about choices in a way guided by this history of choice.”
Whatever course humans take, he said, it must come from a reckoning with their long legacy as children of Earth, and the creation of their minds amid a long “lineage of transforming agents” that have reshaped the planet.
What people do with that, he argued, is up to them.