After several mass extinctions, here is the one caused by the human species. Animals are disappearing, killed for consumption, or unable to survive the pace of change. The success ofHomo sapiens means the death of other living things. It’s no longer “ after us, the flood »: we are the flood.
The idea spread first among ecologists, then to an increasingly wider public: we are witnessing the sixth mass extinction since the appearance of the first animals, of which fossils have been found dating back to 540 million of years. The five previous extinctions occurred at the end of the Ordovician (-445 Ma), the Devonian (-360 Ma), the Permian (-250 Ma), the Triassic (-200 Ma) and finally the Cretaceous (-66 Ma). ), the latter, the most famous, having marked the end of dinosaurs and the advent of mammals.
Each of these extinctions probably had its particular cause. It is generally accepted that the end of the dinosaurs was the consequence of the impact of a gigantic meteorite which struck the Yucatan (today in Mexico). The Ordovician extinction is thought to be the result of relatively rapid glaciation on a geological time scale. ; that of the Permian would be due to rapid warming. The particularity of the sixth extinction is that its origin is human: the catastrophe is us ! Evolution has generated a species whose activity and proliferation have taken on a geological dimension leading to the mass extinction of other species.
Previous extinctions were highlighted by geologists, who noted sudden ruptures of fossil forms in the geological layers (sudden disappearance of species previously present at great depths and appearance of new species present in the new layers). It is moreover these changes which were used to determine the geological periods.
So great is the activity of man that a growing number of geologists admit that its trace is already visible in the sedimentation process which will produce the rocks of tomorrow and that it will therefore be identifiable in millions of years – if a form of intelligent life is still present to carry out this type of research.
Cuvier and Darwin
Elizabeth Kolbert’s work is both the story of species extinctions (current and past) analyzing the mechanisms at play and the story of man’s awareness of, on the one hand, the process of extinction, on the other hand of the extinction in progress. The chapters, and this is the charm of the process adopted by the author, appear like the stages of an investigation during which the present and the past, biological phenomena and scientific controversies intertwine.
It is Cuvier who deserves the credit for having highlighted the existence of catastrophic extinctions in the past. However, he never sided with “ transformism » (the idea that species transform). Above all an anatomist, and noting the perfect concordance of organs – a concordance which allowed him, for example, to know on the basis of a tooth that an animal was herbivorous –, he ruled out the possibility of progressive incremental evolution. Darwin, very influenced by the thoughts of the geologist Lyell, and Wallace, by developing the idea of natural selection, will give a driving force to transformism, which will take the name of “ evolution “. In doing so, they ignore the contradiction between their theories and the geological traces, which rather testify to periods of stability and brutal changes.
For a long time therefore, progressive evolution and mass extinction will hardly seem compatible: natural selection and gradualist evolution were unable to account for mass extinction. It is finally in the post-war decades that a history of evolution will take place, combining progressive evolution, so to speak “ at cruising speed », and phenomenon of mass extinction, followed by accelerated evolution linked to non-biological events, at least until the appearance of this strange form of life which is Homo sapiens. We can regret that the author does not refer to saltationist theories of evolution and, in particular, to the work of Stephen Jay Gould.
Extinction Stories
By its extraction of resources, by its ferocity, by the global warming it causes, by the fragmentation of habitats, by the rapid transfer of plants, animals, bacteria and fungi which become invasive and exterminate local species, Homo sapiens became the vector of the sixth extinction, leading the chemist Crutzen to speak of “ Anthropocene », an age of the Earth of which man is the main parameter. It’s no longer “ after us, the flood » ; we are the flood.
Several factors play a determining role. Above all, it is the spatial scale and speed of the phenomenon that overwhelms the adaptive capacity of species: for many species, change is simply happening too quickly. “ When the world changes faster than the process of adaptation of species, many of them are cut down. »
Elizabeth Kolbert illustrates each phenomenon with stories of extinction: the massacre of the great auks, in XIXe century in particular, exploited for their feathers ; the current disappearance of corals, under the effect of the acidification of the water linked to the increase in the rate of CO2 in the atmosphere ; large herbivores were early victims (between -40,000 and -25,000 years ago) under hunting pressure ; American bats affected by leprosy caused by a European fungus which prevents them from hibernating due to the itching it causes ; but also Neanderthal man, eliminated and partly absorbed, since Europeans owe him all the same 4 % of their genes.
Collaborate to save yourself
While touching the reader with its poignant stories (the description of a visit to a bat hibernation cave, during which she must walk on a carpet of dead animals, brings us closer to the films of Quentin Tarantino) , Elizabeth Kolbert maintains the characteristic style of North American journalism. Personal anecdotes – his night in the jungle, his visit to the Neanderthal museum in Germany, a diving suit one size too small – rub shoulders with numerous portraits of passionate researchers, descriptions of places and atmospheres, which leads to recount his investigation as much as the result. The author is talented and the process is effective, if you like it. It has the merit of giving a little breath and color to a subject that is, after all, very dark and depressing.
The tone always remains educational, descriptive and almost distanced. The author, as a good journalist, strives to report facts, testimony to the process in progress, its causes and the mechanisms at play, but without passing judgment, which is consistent with the concept of a humanity transformed into telluric force or “ as the most successful invasive species in the history of living beings “. If man exterminates, it is apparently in the nature of his dynamics as a species. I admit I found this detached tone a little confusing. What emerges is a disturbing feeling of chronicling a predicted death. And – undoubtedly being unfair – a privileged fatalism.
In the chapter on our less fortunate Neanderthal cousins – as a species that is – we cannot escape the researcher who is interested in the genetic basis of human abilities: “ There must be a genetic basis for this, and it is hidden in these long lists of base pairs. “. While waiting to find the gene of our (in)humanity – the chapter is entitled “ The madness gene » –, the author notes with Michale Tomasello (from the Max-Planck Institute) that it is not a priori individual intelligence that distinguishes man from great apes, but the ability to collaborate: “ Great apes appear not to be adept at collective problem solving, an approach that is of central importance in human society. » Kropotkin, theoretician of anarchism and libertarian communism, would have appreciated it.
Unfortunately, in this case, the problem to be solved seems to be man himself, and perhaps not only for other species. According to paleoanthropologist Richard Leakey, “ Homo sapiens will not only be the cause of the sixth extinction, it will also be one of its victims “. Homo sapiens unable to collaborate to save himself ? It’s possible. The two-decade climate negotiations suggest this.
Life goes on
After each mass extinction, life has rebounded and re-diversified in astonishing ways. Was the disappearance of dinosaurs not the luck of mammals? ? On a geological scale, an extinction is only a bifurcation in evolution, not the end of the evolutionary process. So, after us, whose turn is it? ? “ After a beer or two, the conversation turned to one of Zalasiewicz’s other favorite topics: giant rats. This rodent has followed man to practically every corner of the globe where it has settled. Zalasiewicz believes, and this is the opinion of an expert on evolution and life, that it will one day dominate the world. »
Why not ? After all, isn’t the rat an animal as social as it is aggressive, as prolific as it is opportunistic? ? He will beat man on his own ground, unless he sees himself snatched the spotlight by the corvids, the family of crows and magpies. Too bad for Kropotkin, who had not considered the dark side of mutual aid. It’s a shame that the French publisher chose a misleading subtitle, because, with or without man, life will go on.
Boss, another beer and… to the health of the rats !