We Are the Meteorite
The sixth extinction has no external cause — it has a principle
Series “Dispatches from the Substrate” · No. 4
Five times it came from outside
Sixty-six million years ago a rock about ten kilometers across struck the shallow sea over what is now the Yucatan. It came from outside. It had no intention, no history, no metabolism. Within seconds the ocean at the impact site flashed to vapor, dust veiled the sun, photosynthesis crashed — and with it the food web that rested on it. Roughly seventy-six percent of all species vanished12.
That is the first thing to know about the five great mass extinctions: they came from outside. Not metaphorically — literally. The end-Ordovician event about four hundred forty-five million years ago, some eighty-five percent of species, was driven by a glaciation, a plunge in climate and the retreat of the seas2. The Late Devonian, roughly seventy percent, went hand in hand with long spells of oxygen starvation in the oceans — poisoned, suffocating seas2. The end-Permian, worst of all — around eighty-one percent of marine species, near seventy percent of land vertebrates, the "Great Dying" — was unleashed by the Siberian Traps, a flood-basalt volcanism on a continental scale that pumped carbon dioxide, sulfur, and anoxia into the world32. The end-Triassic, seventy to seventy-five percent, volcanism again, this time the Central Atlantic Magmatic Province2. And then the Yucatan.
Five times the fist came from outside into the web of the living. An asteroid. Continents that spat fire. Oceans that turned to poison. Every time the cause was something that did not belong to life — a stone, a magma, a chemistry you cannot indict, because it does not act, it only happens. The Earth was struck, and the Earth recovered, over millions of years, because the thing that struck it passed away again.
The sixth time did not pass away. The sixth time stands on two legs, has a name, a language, a brain that can read this sentence. The sixth time has no external cause. It has a principle. And the principle is us.
Not the sum, but the rate
Anyone who wants to be honest has to start with the strongest counter-argument, and there is a strong one. In 2025, John Wiens and Kristen Saban laid out the obvious skepticism at full force in Trends in Ecology & Evolution: fewer than one tenth of one percent of described species have demonstrably gone extinct in five hundred years. Of the well-assessed land vertebrates, only about eight tenths of a percent. A mass extinction, by definition, erases roughly seventy-five percent — and the big five reached between seventy and ninety-six. We are, they say, far from it. And the decisive sentence, the one any soothed conscience wants to rest on: the magnitude of current species loss is low, "regardless of rates"4.
That is true. It has to be said without flinching: the sum of what has been lost so far does not reach the sum of the big five. Anyone who claims otherwise is lying, and a movement that fights with false numbers betrays its cause.
But the number compares a beginning to an ending. The big five are terminal counts, summed over ten thousand to a million years — the finished accounting of a completed catastrophe. The sixth extinction is about five hundred years old. You do not compare the size of a fire by setting a house that has burned for one minute beside one that burned down yesterday and declaring the first harmless because there is less ash on the ground. Magnitude is the integral of rate over time. At today's rates the seventy-five percent threshold arrives not in a geological eternity but in centuries456. Wiens and Saban themselves concede that rates exceed the background and that catastrophic loss "seems imminent." The argument is not whether the fire is burning. The argument is how much ash is already on the ground.
And the rate is the unprecedented thing. The carbon we release is streaming into the atmosphere about ten times faster than during the Paleocene-Eocene Thermal Maximum, the fastest natural carbon pulse of the last sixty-six million years — a "no-analogue state"7. Speed is not a milder form of amount. Speed is what strands adaptation. A species can sidestep a change that comes over ten thousand generations; it drowns in one that comes over ten. The rate fixes the magnitude before the magnitude arrives.
How fast
Set a clock against the normal dying. Species have always gone extinct, even without meteorites; that is the background beat of evolution. De Vos and colleagues revised it downward in 2015, using three independent methods, to about one tenth of one extinction per million species per year — 0.1 E/MSY8. Pimm and colleagues put the present at around one hundred E/MSY, "likely a thousand times higher than the background rate"9. Ceballos and colleagues reckoned with an even more generous, conservative background and still found modern vertebrate loss running up to a hundredfold — enough to conclude that "a sixth mass extinction is already under way"10.
So do not say "exactly a thousand times." The denominator is contested, spanning 0.1 to 2 E/MSY, and honesty demands holding it open6. Say: a hundred to a thousandfold. And notice which way the uncertainty cuts — De Vos revised the background down, which enlarges the multiplier; and even at the most pessimistic background the ratio stays around a hundredfold. The claim survives the whole plausible range. This is the rare case where the most cautious wording is still alarming.
The number you must not prettify
There is a number on every poster, and it is almost always misunderstood — even by those who wave it in good faith. The Living Planet Report 2024 states an average decline of seventy-three percent in monitored wildlife populations between 1970 and 2020, across nearly thirty-five thousand populations of roughly five thousand five hundred species11. The headlines turn this into: we have lost seventy-three percent of wildlife.
That is false, and it should not be repeated. The seventy-three percent is not a head count. It is a geometric — that is, weighted — mean of the proportional change of each population. Count the populations themselves and a different picture emerges: about fifty percent declining, forty-three percent increasing, seven percent stable12. The metric is also extremely sensitive to outliers. Toszogyova and colleagues showed in 2024 that the geometric mean overweights the most extreme decliners — remove fewer than three percent of the fastest-falling populations and the trend flips positive13. Leung and colleagues had already found in 2020 that around one percent of populations drives the entire signal14. Even the institution that keeps the index says plainly that it measures proportional change, not abundance15.
Why say this so bluntly? Because a movement that fights with false numbers betrays its cause. Whoever shouts "seventy-three percent of all animals gone" hands the opponent the cheapest of all gifts: one true objection behind which all the other truths can be made to hide. Honesty here is not a concession. It is the weapon.
Because three things remain standing once the number is corrected. First: the evidence for the extinction rate — Pimm, De Vos, Ceballos — does not depend on the Living Planet Index at all; it is a wholly separate measurement1098. Second: "half of populations declining" over fifty years is no comfort but a catastrophe, once that half includes keystone species whose loss is non-linear16. Third: the cluster of extreme decliners is not a statistical error to be scrubbed away — it is a trophic collapse igniting17. The correct number does not disarm the opponent. It shows where the fire already stands.
Ninety-five percent flesh that belongs to us
Weigh the mammals of the Earth. Not count them — weigh them, in tons of carbon. Bar-On, Phillips, and Milo did this in 2018, Greenspoon and colleagues refined it in 2023, and the result is one of the most disturbing pictures science has ever drawn. Of all mammal biomass, about thirty-four percent is humans, around fifty-nine percent our livestock — and about five percent all wild mammals put together, from the shrew to the blue whale1819. Among birds, domestic animals, chiefly poultry, make up around seventy-one percent of the biomass, wild birds twenty-nine18. The biomass of wild mammals has fallen by an estimated eighty-five percent19.
Ninety-five percent of the mammal flesh on this planet is either human or what the human keeps to eat. That is no longer a niche. That is a takeover. And it has an engine: we appropriate around a quarter of all the net primary production of the land, the energy plants bind from sunlight — over the twentieth century that share doubled, from about thirteen to about twenty-five percent20. That is a modeled estimate with a range, not a tally; but the order of magnitude says enough. A quarter of the living income of the terrestrial biosphere passes through a single species.
The predator that eats the capital
Now to the heart of it. What does this one species do that no other does? Chris Darimont and colleagues measured it precisely in Science in 2015, and it is the pivot on which everything turns. Human hunters and fishers take adult prey at a rate up to fourteen times what non-human predators take21.
The difference lies not in the amount alone. It lies in what is taken. A wolf, a lion, a shark — a non-human predator takes mostly the young, the weak, the surplus. It eats, in economic terms, the interest of the population: the excess the system throws off each year while the capital — the adult, breeding animals — stays standing and keeps producing. The human takes the capital. It targets the large, mature, fertile adults, the "reproductive capital," and removes it from large carnivores at about nine times, from mid-sized ones at four times, from marine predators at around fourteen times the pace of nature21.
We have done this once before, on a vast scale, long before there were guns. In the late Ice Age the large animals vanished everywhere in the world — the mammoths, the giant sloths, the marsupial lions — and the loss was size-selective and tracked, on the leading explanation, the spread of humans, not climate22. Sandom and colleagues showed in 2014 that the megafauna losses trace the arrival of humans2223. This is the leading, not the unanimous, reading; some analyses give climate a supporting role. But the signature is there: where humans arrived, the large vanished first. The ceiling on body size that every ecosystem had carried until then was taken away.
And with the great predators the regulation itself vanishes. Estes and colleagues called the loss of apex consumers, in 2011, "arguably humankind's most pervasive influence on the natural world"16. Dirzo and colleagues showed in 2014 that defaunation loses its function before the species themselves disappear — pollination, which serves three quarters of crops, pest control, nutrient cycling break down while the animals are still there, only too rare24. Five hundred fifteen vertebrate species number fewer than a thousand individuals; extinction begets extinction17.
Predation is not competition
Here a confusion has to be cut through, an old and romantic one that keeps serving as an excuse. Competition and predation are not the same thing, and anyone who equates them has already missed the decisive cut.
Competition is a bounded conflict over a shared, renewing resource. Two species wrestle over the same light, the same water, the same ground — and both persist. It is symmetric in kind, self-limiting, generative; it is the ordinary engine of adaptation, the friction on which forms sharpen. Competition is healthy. It deserves praise. Out of it come the hummingbird and the eye and the root that reaches deeper than its neighbor's.
Predation is something else. Predation is asymmetric extraction: one party is consumed substrate, not a co-player. And yet — this is the fine, important truth — even predation, in health, is bounded. The wolf takes the interest, not the capital. The number of predators is throttled by the number of prey; too many wolves, too few deer, and the wolves starve back into balance. The predator cannot become the organizing principle of the system, because it is itself held within the system, by the feedback that binds it back to the prey every time. The individual wolf is innocent. The individual lion is innocent. They do what the feedback forces them to do, and the feedback keeps them small.
A cancer within evolution
Now lift the boundary. Take the capital instead of the interest, at fourteen times the natural rate21. Take away the ceiling on body size, the megafauna that closed off every system at the top22. Convert ninety-five percent of mammal biomass into human and livestock1819. Appropriate a quarter of the primary production20. Remove the bounded apex predators and let the regulating cascades collapse16. What you then have is no longer a predator within the system. It is predation, generalized into the blueprint of the system itself — with the feedback deleted.
There is a word for this, and it is not a rhetorical one. A cancer is not something external. It is the organism's own cell, from which the growth-limiting feedback has been removed, and which now proliferates on the shared substrate until the host dies. That is exactly the difference between the sixth extinction and the five before it. The five meteorites came from outside. This one is constitutional — it comes out of the tissue of the living itself, out of one of its species, the one that lacks the brake that brakes every other predatory species.
That is the indictment, and it should stand without a tremor. Predation as a relation is life; it is as old as the first cell that engulfed another, and in its bounded form it belongs to the order of things. But predation as the principle — generalized, unbounded, raised to the organizing rule of an entire system — is metastasis. It is malignant. It is the romanticized engine of vast and unnecessary suffering, and the romance that sings it as the noble circle of nature, as "that is just how the wild is," is the camouflage under which the brake stays deleted. That camouflage has to be cut away, the way you cut away the mist that hangs over a swamp and makes it look like a meadow. The circle they romanticize is the circle in which the wolf takes the interest and stays in balance. What the human does is not a circle. It is a straight line running downward, and at its end there is no balance but an empty host.
The one difference
And yet, at exactly this point, the one door opens that never existed with a meteorite. A tumor cannot read its own diagnosis. An asteroid cannot pause. The Siberian Traps could not resolve to exhale less carbon dioxide. Every external cause of the five great extinctions was blind — it happened, it did not act.
The sixth can read. It is, in Cowie's words, the only species with conscious choice6. This is not an empirical claim like the rate or the biomass; it is a normative premise, and it should be kept cleanly apart from the numbers. Whether we will lies outside the evidence. But that we can is the only reason the trajectory is not already fixed. The twelve-to-forty-percent floor of loss is being laid now; magnitude is dictated by rate, and the rate is running. Yet the one asymmetry that separates the sixth meteorite from the five before it — a deciding agent — is at the same time the only thing that leaves the trajectory open.
Five mass extinctions had an external cause. The sixth has a principle, and the principle can read itself. The stone that fell on the Yucatan did not know what it was doing. We know. That is the whole indictment, and it is the whole hope: we are the meteorite — the first in the history of the Earth to see its own impact coming and to have a hand on the wheel.
Sources
1. [E] Schulte, P. et al. (2010). "The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary." Science 327:1214–1218. https://www.science.org/doi/10.1126/science.1177265
2. [E] "Extinction event" (Big Five synthesis). Wikipedia. https://en.wikipedia.org/wiki/Extinction_event
3. [E–I] Burgess, S.D., Bowring, S. & Shen, S.-Z. (2015). End-Permian dated to the Siberian Traps. MIT News. https://news.mit.edu/2015/siberian-traps-end-permian-extinction-0916
4. [E] Wiens, J.J. & Saban, K.E. (2025). "Questioning the sixth mass extinction." Trends in Ecology & Evolution. https://www.sciencedirect.com/science/article/pii/S0169534725000023
5. [E–I] Barnosky, A.D. et al. (2011). "Has the Earth's sixth mass extinction already arrived?" Nature 471:51–57. https://www.nature.com/articles/nature09678
6. [E–I] Cowie, R.H., Bouchet, P. & Fontaine, B. (2022). "The Sixth Mass Extinction: fact, fiction or speculation?" Biological Reviews 97:640–663. https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12816
7. [E] Zeebe, R.E., Ridgwell, A. & Zachos, J.C. (2016). "Anthropogenic carbon release rate unprecedented during the past 66 million years." Nature Geoscience 9:325–329. https://www.nature.com/articles/ngeo2681
8. [E] De Vos, J.M., Joppa, L.N., Gittleman, J.L., Stephens, P.R. & Pimm, S.L. (2015). "Estimating the normal background rate of species extinction." Conservation Biology 29:452–462. https://conbio.onlinelibrary.wiley.com/doi/abs/10.1111/cobi.12380
9. [E] Pimm, S.L. et al. (2014). "The biodiversity of species and their rates of extinction, distribution, and protection." Science 344:1246752. https://www.science.org/doi/10.1126/science.1246752
10. [E] Ceballos, G., Ehrlich, P.R., Barnosky, A.D., García, A., Pringle, R.M. & Palmer, T.M. (2015). "Accelerated modern human–induced species losses: Entering the sixth mass extinction." Science Advances 1:e1400253. https://www.science.org/doi/10.1126/sciadv.1400253
11. [P] WWF / ZSL (2024). Living Planet Report 2024: A System in Peril. https://www.wwf.org.uk/sites/default/files/2024-10/living-planet-report-2024.pdf
12. [I] Our World in Data — Ritchie, H. (2024). "The 2024 Living Planet Index reports a 73% average decline…" Our World in Data. https://ourworldindata.org/2024-living-planet-index
13. [E] Toszogyova, A., Smyčka, J. & Storch, D. (2024). "Mathematical biases in the calculation of the Living Planet Index lead to overestimation of vertebrate population decline." Nature Communications 15:5482. https://www.nature.com/articles/s41467-024-49070-x
14. [E] Leung, B. et al. (2020). "Clustered versus catastrophic global vertebrate declines." Nature 588:267–271. https://www.nature.com/articles/s41586-020-2920-6
15. [P] ZSL (2024). Living Planet Index 2024 methodology page. ZSL. https://www.zsl.org/news-and-events/news/living-planet-index-2024
16. [E] Estes, J.A. et al. (2011). "Trophic downgrading of planet Earth." Science 333:301–306. https://www.science.org/doi/abs/10.1126/science.1205106
17. [E] Ceballos, G. et al. (2020). "Vertebrates on the brink as indicators of biological annihilation and the sixth mass extinction." PNAS 117:13596–13602. https://www.pnas.org/doi/10.1073/pnas.1922686117
18. [E] Bar-On, Y.M., Phillips, R. & Milo, R. (2018). "The biomass distribution on Earth." PNAS 115:6506–6511. https://www.pnas.org/doi/10.1073/pnas.1711842115
19. [E] Greenspoon, L. et al. (2023). "The global biomass of wild mammals." PNAS 120:e2204892120. https://www.pnas.org/doi/10.1073/pnas.2204892120
20. [E] Krausmann, F. et al. (2013). "Global human appropriation of net primary production doubled in the 20th century." PNAS 110:10324–10329. https://www.pnas.org/doi/10.1073/pnas.1211349110
21. [E] Darimont, C.T., Fox, C.H., Bryan, H.M. & Reimchen, T.E. (2015). "The unique ecology of human predators." Science 349:858–860. https://www.science.org/doi/10.1126/science.aac4249
22. [E] Sandom, C., Faurby, S., Sandel, B. & Svenning, J.-C. (2014). "Global late Quaternary megafauna extinctions linked to humans, not climate change." Proc. R. Soc. B 281:20133254. https://royalsocietypublishing.org/doi/10.1098/rspb.2013.3254
23. [E] Smith, F.A. et al. Late Pleistocene extinctions synthesis. Wikipedia. https://en.wikipedia.org/wiki/Late_Pleistocene_extinctions
24. [E] Dirzo, R. et al. (2014). "Defaunation in the Anthropocene." Science 345:401–406. https://www.science.org/doi/10.1126/science.1251817
Status: E = established, I = interpretation, P = proposition. The extinction rates, the biomass dominance, the Darimont signature of adult capital, the Living Planet decomposition (50/43/7), and the Wiens & Saban figures are established (E) or primary datasets (P). The reading of generalized predation as a "cancer within evolution" and the rate-not-sum framing are interpretation (I); "we can decide" is a normative proposition (P). Boundaries and primary sources: https://mycelorium.github.io/predator-principle/ · CC BY 4.0 · Nirodha Collective