In a post-apocalyptic future, what would happen to life if humans disappeared? After all, it is likely that the human species extinguishes long before the sun turns into a gigantic red ball and ends with all living beings on the face of the Earth.
Assuming we do not end up with other living beings before (something unlikely despite our tendency to make species disappear ), history tells us that there will be fundamental changes once humans cease to be the dominant animal species on the planet.
So, if we could take a leap in time to about 50 million years after our disappearance, what would we find? What animal or group of animals would relieve us as a dominant species? Will a Planet of the Apes be born like that of the movies? Or will dolphins, rats, tardigrades, cockroaches, pigs or ants dominate the Earth?
This question has given rise to many speculations, and numerous writers have made lists of candidate species. However, before making conjectures, we must explain what we mean by dominant species.
Let’s confine ourselves to the animal kingdom
You could say that the current era is the era of flowers. However, when viewing the future no one imagines Audrey 2 from The Tent of Horrors (although the triffids of fiction had characteristic features of animals, such as predatory behavior and the ability to move).
Let us limit ourselves to the animal kingdom, more for practical than philosophical reasons. According to certain criteria, the world has always been dominated by bacteria, despite the fact that the ” era of bacteria ” ended around 1.2 billion years ago. But it was not because the bacteria ceased to exist or because their predominance decreased, but because we tend to give more importance to the large multicellular organisms that came later.
According to some calculations, four out of every five animals are nematodes (cylindrical worms). So, with these examples, it is clear that neither prevalence, nor abundance, nor diversity are essential to be the dominant way of life. Instead, our tendency is to think of large and charismatic organisms.
The meek will inherit the Earth
There is an indisputable degree of narcissism in how humans designate dominant species, as well as a tendency to give this title to our close relatives. Planet of the Apes imagines that our primate relatives could develop speech and adopt our technology if we gave them enough time and space.
But it is unlikely that nonhuman primate societies inherit our dominion over the Earth since, probably, the apes will be extinct before us. We are already the only living hominid that is not in danger of extinction. And it is not likely that the crisis that could end our species left the other great apes aside. In fact, any type of extinction that affects humans would also be dangerous for those organisms with similar basic physiological needs.
Although humans succumb to a global pandemic that affects few mammals, the great apes are, precisely, the species most at risk of contracting new diseases that could eliminate them from Earth.
Can another relative, more distant, (primate, mammal or otherwise) develop intelligence and a society similar to ours? That does not seem likely either. Of all the species that, in theory, have been dominant animals at some time, humans are unique in their exceptional intelligence and manual dexterity. It can be deduced, therefore, that such qualities are not a requirement to be the dominant species or to evolve. Evolution does not favor intelligence by itself unless it leads to a higher level of survival and reproduction. Therefore, it is a serious mistake to think that our successors will be especially intelligent, that they will be social beings, that they will be able to speak or that they will be experts in technology.
So, can we say something about the dominant species 50 million years after the extinction of the human being? The answer is as disappointing as surprising. We can be pretty sure he will not be a talking chimp, but we have no idea what it will be.
The Earth has seen a great number of massive extinctions throughout its history. The diversification of life after each event has always been relatively rapid and the adaptation of the new species produced new life forms very different from those that engendered them after surviving the previous extinction.
The small creatures that ran under the feet of the dinosaurs at the end of the Cretaceous period were very different from the cave bears, the mastodons and the whales descended from the Age of the Mammals. Likewise, the reptiles that survived the massive extinction of the Permian-Triassic about 250 million years ago, which ended with 90% of marine species and 70% of terrestrial species, also did not resemble pterosaurs, dinosaurs, mammals and birds that descended from them.
In The Wonderful Life: Burgess Shale and the nature of history, the late Stephen J. Gould argued that chance, or contingency, as he used to say, played a very important role in the great transitions of animal life. There is room to argue about the relative importance of contingency in the history of life, which remains a controversial issue today. However, Gould’s perception that the survival of modern races can hardly be presaged after a future extinction is a lesson in humility about the complexity of evolutionary transitions.
Although it could happen that the ants take us into the domain of the Earth, as has been speculated, it is impossible for us to know how those dominant ants will be descendants of the current ones.