If humans can’t tell right from wrong, everyone’s screwed.
IT IS SAID that we are at the beginning of another mass extinction of life, defined as a time when over 75% of species vanish.
The extraordinary story of life on Earth, which likely began about 3.5 billion years ago, includes vast episodes of extinction, rebirth, and relative stability of life. The first living beings were not powered directly by free oxygen (which was absent from Earth’s atmosphere) but indirectly via hydrogen peroxide from crushed or weathered silicate rocks. Some of these anaerobic microbes developed an ingenious biochemical way to capture photons from the Sun for energy. With that energy, they transformed carbon dioxide and water to feed themselves and, in the process, released oxygen, eventually tons of it.
These cyanobacteria exploded in number forcing an atmospheric “Great Oxidation Event.” Life was about to be “burned up” (molecular O2 is very chemically reactive), or at best faced with a future of chronic oxygen toxicity.
But hold on—no worries! New generations of cyanobacteria found an amazing way to use (and consequentially draw down) atmospheric oxygen in the process of creating themselves!
These beings, so fundamental to complex life far into the future, lived billions of years ago. Let’s thank primeval cyanobacteria for planetary oxygenation and certainly others of their kind for getting oxygen overshoot under control.
(A word of caution: we’re far from having a full understanding of the coevolution of solid Earth, life, and atmosphere. “Deep time” is very unsettled history. What’s said here is “to the best of my knowledge” of what scientists have found).
Flash forward to about a half a billion years before us, to the advent of five famous mass extinctions. We pay most attention to these extinctions because they occurred at a time in history when the Earth first housed complex plants, insects, fishes, corals, four-footed animals, and other “modern” forms of life.
While the extinctions opened opportunities for new ways of living, they also terminated vast numbers of beings and entire forms of life. This is no small matter, especially as Earth time begins to wind down. (More on this in a bit).
Here’s a brief rundown on the “big five” extinctions. As you might guess, they can’t explain today’s unfolding tragedy. Nonetheless, they are a huge part of our scientific and philosophical discourse on how we got here and where the world is headed.
“Recent” Mass Extinctions in chronological order, each of which ended a geological period (they’re often written with the prefix End- which I’ve omitted here):
Ordovician (roughly 440 million years ago) — Ice ages forced a sharp decline in life, all of which was marine life at the time. When plants colonized the supercontinent Gondwana, they removed huge amounts of carbon dioxide directly from the atmosphere, and indirectly by accelerating rock weathering. At the same time, Gondwana shifted toward Earth’s coolest region — the South Pole. Some scientists dispute this narrative, arguing that volcanoes periodically released vast quantities of greenhouse gases that forced global heating and extinctions.
Devonian (~370 Mya) — Like the first, this second mass extinction was triggered by glaciation and a lowering of global sea level. Again, the likely cause was the expansion of life itself. Plants first colonized land in what’s referred to as the Devonian explosion. Forests stored great amounts of atmospheric carbon dioxide, which cooled down the planet to the ultimate detriment of much life, including the first land-living animals. Open-water swimmers such as sharks and bony fish survived the extinction, while nearly all the bottom fish disappeared likely because of oxygen deprivation triggered by enormous algal blooms fed by nutrient runoff from the land.
Some scientists believe that volcanism was again a factor, releasing huge amounts of greenhouse gases over what became a 25-million year period of climate change, ecological instability, and extinction.
Permian (~250 Mya) — Massive volcanic eruptions released tremendous quantities of carbon dioxide that forced global heating. The Permian “Great Dying” resulted in the disappearance of over 96% of marine species (as CO2 acidified the oceans) and 70% of terrestrial species, including many insects.
Was volcanism enough to cause such great loss of life? The late Permian also saw vast blooms of methane-producing single-celled Archer and assembly of the supercontinent Pangea which ultimately destroyed shallow marine basins and altered ocean currents. An astroid hit, if it occurred as some believe, didn’t help.
As one geologist surmised, maybe everything—eruptions, an impact, anoxia—went wrong at once. It took perhaps 10 million years for life to rebound from the devastation caused by the Great Dying. Surviving plants would need a lot of time to draw down catastrophic concentrations of atmospheric carbon dioxide.
Triassic (~225 Mya). Earth experienced a quadrupling of atmospheric CO2 that elevated global temperatures by 5 to 11 degrees F. The late Triassic saw colossal lava flows from a huge continental igneous province (the Central Atlantic), with enough output to cover an area the size of the continental U.S. in quarter-mile thick basaltic rock. Rising CO2 concentrations acidified the oceans to the destruction of much life. The Triassic extinction eliminated some 76% of all marine and terrestrial species, and triggered a shift among dominant vertebrates from crocodilians to dinosaurs.
Cretaceous (~65 Mya) — Everybody is familiar with the most recent mass extinction: a huge asteroid hits Earth kicking up vast clouds of dust, sunlight is blocked, global temperatures drop, and plant life diminishes, with corresponding extinctions of animal life throughout the food web. The event most notably caused the extinction of those dominant beings, the dinosaurs (except for their bird lineage), which cleared the way for the evolutionary rise of mammals. Another massive volcanic outpouring may also have occurred during the Cretaceous, this time, however, benefiting life by lessening the degree of global cooling caused by the asteroid hit.
Is Earth on the cusp of a sixth mass extinction?
Our destruction of animal and plant life today is dreadful and, from a moral perspective, represents the Greatest Injustice of All Time.
Human impacts on other species began in earnest as people dispersed out of Africa. Much of the damage was to larger animals, most notably the megafauna of Australia (~40,000 years ago) and of North America (~12,000 years ago).
A second wave of destruction commenced as humans “settled” land, cleared natural habitats and exploited resources essential for other life. This wave greatly accelerated with scaled-up agriculture, a corresponding surge in human numbers, and widespread use of fossil fuels to power what became a vast global civilization.
Is human activity now causing devastation to match that of past mass extinctions? The answer is not yet — but it’s starting to look that way.
Past extinctions don’t explain what’s happening today
The Earth is not undergoing mass volcanism as it did during the Permian and Triassic periods, and is unlikely anytime soon to be hit by a giant bolide like the one that ended the Cretaceous. But Earth does have us, a pesky organism far different from the beings that triggered the “Great Oxidation” billions of years ago, and the plant life that over many millennia led to Ordovician and Devonian ice ages.
Based on previous mass extinctions, one might get the impression that life is constantly undergoing horrific turmoil. However, episodes of mass extinction extended over less than 15% of the past 600 million years (by my rough estimate). Vast stretches of time saw relative tranquility, which would characterize the world today if it were not for one fact—our moral culpability.
Does evolution compel us to destroy?
Humans obviously have many advantageous traits, including an exceptional ability to exploit other life. Long ago, human groups that best did so improved their prospects for survival and prosperity.
When food resources diminished from overexploitation or other factors, humans most capable at switching to other resources flourished. Successful Paleolithic people, for example, who locally depleted mammoths and other large prey, turned to smaller animals or moved to another location.
Recently, a team of evolutionary biologists described how evolution shaped humans for group adaptation and survival, not global-scale problem solving. As Tim Waring, the lead author of the paper, grimly put it, "We don't have any solutions for this idea of a long-term evolutionary trap.”
Is evolution responsible for the current surge in extinctions? We would be unwise to believe so. Sure, evolution predisposed us to spread around the world with transformative technologies. But it also gave us a capacity to set rules and distinguish right from wrong.
We take great pride in being “moral agents.” Some say that status is a big deal because it sets us apart from the rest of life on Earth. Unfortunately, this is used to justify human supremacy, the exclusion of more-than-human life from serious moral consideration. Essentially, the argument goes, since other life can’t morally reciprocate, it doesn't deserve rights. This “moral agency” debate has been going on for as long as I can remember.
But let’s flip the argument to say that our moral exceptionalism is the ticket out of an evolutionary trap. It is the one thing that could avert a sixth mass extinction, one that may well include us.
The renowned wildlife biologist Aldo Leopold believed “the extension of ethics is actually a process in ecological evolution,” that an ethic “is a limitation on freedom of action in the struggle for existence.”
Leopold went on to say:
The first ethics dealt with the relation between individuals; the Mosaic Decalogue is an example. Later accretions deal with the relation between the individual and society…There is as yet no ethic dealing with man’s relation to land and to the animals and plants which grow upon it…The extension of ethics to this third element is, if I read the evidence correctly, an evolutionary possibility and an ecological necessity.
An ecological necessity
We won’t have a livable planet unless we develop a non-hierarchical set of moral principles that include more-than-human life. At great peril to ourselves, we mistreat life that is part and parcel of the same environment that we are.
A broad life-affirming morality would, I suggest, also mitigate conflicts among us (the worst of which may lead to nuclear war). By embracing an ethical responsibility to safeguard all life, we might take our responsibility toward fellow humans more seriously.
Unfortunately, our civilization is so full of itself that it believes a sixth mass extinction can be avoided simply through better governance—“through policy changes that increase conservation efforts and curb our production of greenhouse gases.” Or more incredulously, “by building technology, solutions and processes that can help us secure animal DNA and begin to reverse the damage created by humans.” I say baloney!
The reality is that our presence on Earth is now so scaled-up that it has become unmanageable. And I don’t think that a world-wide regulatory system or authority, even if that were socially and politically possible, would end our overexploitation of life.
An evolutionary possibility
The extreme anthropocentrism that characterizes our civilization is rooted in technological arrogance, blind faith in human-like gods, and an obsession with growth of the human enterprise. Yet throughout much of history, people related to other living beings in a different way, non-hierarchically and in kinship with them. These beliefs sometimes (but not always) constrained exploitation of life. Direct reliance on what nature provides and low population densities meant little or no destruction of ecosystems for nonhuman life.
By contrast, our industrial civilization’s sense of right and wrong is strictly tied to “our species.” Our morality is narcissistic. It locks out our living relations—namely, the rest of life on Earth.
But hear ye, nothing is impossible. There are signs of an evolving morality that includes more-than-human life. I find hope in the ecocentric, half earth, and rewilding movements, in world scientists who speak out on the matter of human misbehavior, in millions of ordinary people and religious leaders who love, respect, and seek to protect wildlife, and in wider acceptance of biocentric Indigenous beliefs and cultures.
We’d be a truly exceptional species if we put an end to our mass destruction of life. To do so, we’ll need a greatly expanded sense of morality, indeed, a biocentric revolution. Unlikely in the short term perhaps—but not impossible.
Is time running out?
Gaia is life on Earth, as some call her. She was born 3.5 billion years ago with a life expectancy of 5 billion years. In terms of our average human lifespan (70 years globally), she is nearly 50 years old. We and all our relations alive today are somewhat late comers to this only known paradise in the universe.
The Sun will recall Gaia about 1.5 billion years from now. What transpires during that time will depend on the strength of our moral compass, at the very least in the short run. Will we force a mass extinction? Or, will we realize our full moral potential as human beings?
What accounts and counts for life on Earth is every precious moment on the grand stage of evolution.
Excellent summary of the mass extinctions!
So what about the current threatened extinction? How is it progressing?
How many species were lost in the Cretaceous-Paleogene Extinction?
>>Some 76 percent of all species on the planet, including all nonavian dinosaurs, went extinct.<<
How long did it take? About 32,000 years.
I have not found an actual number of species lost.
>>Scientists have estimated that there are around 8.7 million species of plants and animals in existence.<<
I haven't found a similar number for the Cretaceous, so let's name a conservative estimate: 1 million species.
76% of 1 million is 760,000. 760,000 species extinct.
How many have gone extinct recently?
>>In the last 500 years, human activity is known to have forced 869 species to extinction (or extinction in the wild). <<
So we are 869 / 760,000 of the way through the current mass extinction.
What if the process speeds up? What if over the next 500 years the process becomes 100 times faster?
86,900 / 760,000 = 11%
In another 500 years we will be 11% through the current mass extinction. Only a short time compared to 32,000 years.
>>But let’s flip the argument to say that our moral exceptionalism is the ticket out of an evolutionary trap. It is the one thing that could avert a sixth mass extinction, one that may well include us. <<
The Earth's population will begin to fall in this century. Given current projections for fertility rates, in 500 years the Earth's population will be between zero and 1 billion. This will undoubtedly terminate the current human-caused extinctions well before it can be considered a mass extinction.
Why are fertility rates plummeting? Because of selfishness and modern contraceptives. It's a lot easier to live these days if you have one or two kids rather than six.
So a moral revolution is not the only prospect for saving nature. We can just be selfish.
That doesn't make as nice a story though, does it?
Rodes.pub/OneBillion
Great review and it does provide clarity about us humans being the current main cause of the on-going mass extinction. It's the I = PAT thing in action. As a biologist, it's so obvious that we are dooming and doing in lots of our fellow living creatures. I am personally doing what I can to reduce the carnage, but the downward spiral advances. I cringe at people who buy "collapse" and act as if the loss of species is totally out of their control and not their problem, seeming like pathetic fatalistic religious types. I suppose you can just be Zen about it, but then again there are so many things we can all do to stop the extinctions. Don't have kids is probably the biggest although not so easy. You can buy habitat, support land trusts, etc! You can do all kinds of things on your own property to improve conditions for lots of species simply by not being so manic about lawn care - let it grow, leave the leaves, plant lots of native butterfly and bird-supportive plants. You can give to organizations helping wildlife and species. You can support protected areas, national parks, wilderness areas, even by going to visit them to incentivize local communities to keep protecting them. Getting the word out is important to, so thanks for doing that with your creative and thought-provoking essays.