A team of scientists has reconstructed the genome of the oldest common ancestor of all mammals, named Morganucodon oehleri, which rubbed the shoulders of dinosaurs 200 million years ago. A window into the past that questions the status of mammals in the evolution of life. Lighting with Bergson and Teilhard de Chardin.
So what is a mammal? Lamarck gives this meaning to it zoological philosophy (1809): “Animals with nipples, with four articulated limbs, and all the vital organs of the most perfect animals. Hair on some parts of the body. »
And add, immediately, a value judgment that became standard in his time, and still remains in many respects: “The mammals […] must be clearly found at one end of the animal chain, and placed where the most perfect animal is offered, and the richest in organization and abilities; for among them alone there are those with the most developed intelligence,” which ends with the human species. Mammals, in other words, form the pinnacle of animal evolution, and humans are the highest point of that pinnacle.
The same “vital impetus” in animals
This decidedly linear view of evolution has been challenged by many thinkers, chief among them Bergson. For the philosopher, evolution is primarily plural, as he explains Creative Evolution (1907): it unfolds along several distinct lines in which such and such dimensions are the same “vital forces”. It is impossible to prioritize these different lines.
The most primitive mammal is probably physiologically more complex than an ant. But one can rightly assume that his social life and his technical ingenuity are infinitely less rich than those of the tiny arthropods that have managed to colonize the entire planet. “A species that claims the whole world as its domain is truly a dominant species and therefore superior. Such is the type of man, who will represent the culmination of the evolution of Vertebrates. But so also, in the Articulated series, are the Insects and particularly some Hymenoptera. It is said that ants are masters of the underground, as man is master of the earth.wrote Bergson.
Plants, instinct, intelligence
If Bergson emphasizes the plurality of lines of evolution, these lines relate to three trends inherent in the original élan vital, coexisting and always deepening one at the expense of the other. A habit is really leading, because of the finitude of ” strength immanent in life”. “The powers immanent in life and first confused […] had to separate growing up. »
These three tendencies are, according to Bergson:
- The vegetative line: this habit, at the highest point developed in the tree, indicates an immobilization and an unconsciousness of the organism, to obtain protection. “The plant cell surrounds itself with a cellulose membrane that condemns it to immobility. » But this habit is still expressed in some animals: “The hard and calcareous skin of the Echinoderm, the shell of the Mollusc, the carapace of the Crustacean and the ganoid cuirass of the ancient Pisces” all expressions of this vegetative tendency. “This cuirass, in which the animal takes refuge, hinders its movements and sometimes cannot move. If the plant turns away from consciousness by wrapping itself in a membrane of cellulose, the animal that confines itself in a fortress or wearing armor condemns oneself to half sleep. »
- The instinct line: ” nakedOn the other hand, instinct is not so developed as in the insect world, and in no group of insects is it so remarkable as in the Hymenoptera”. The instinct is realized through a deeper and deeper specialization of the organs, and through a more and more assertive functional adaptation of the organism to its environment. In insects, the body is encased in an exoskeleton “consists of a more or less long series of interlocking rings; The motor activity is then distributed among a variable, sometimes large, number of appendages, each of which has its own specialty. » This kind of behavior is assured of immediate success but limited in its effects” due to the specialization of the organism. Insect societies reflect this strict specialization: “wonderfully disciplined and united”, “but frozen”.
- The smart linethis: this is the line that ends the mammalsand finally to the people. “smart”is the ability “to represent the relations of external things to each other, finally to think about matter” for’“ensure the perfect entry of our body into its environment”. The “comprehension” is “an appendix to the faculty of acting, an adaptation more and more precise, more and more complex and flexible, of the consciousness of living beings to the conditions of existence made for them.” Intelligence allows the ability to adapt to changing environmental conditions, which is more flexible than physiological adaptation.
In many ways, it should be emphasized how vertebrates, and more so mammals, show sub-specialization compared to insects. “The activity is focused only on two pairs of legs, and these organs perform functions that do not depend much on their shape. » This sub-specialization seems to be compensated by the inventiveness, the intelligence, in other words the freedom of a psychism capable of discovering, in its versatile members, new possibilities of action. “Freedom becomes perfect in man, whose hand can do any work. » This independence is reflected in social organization: mammalian society ” are open to all progress, but divided, and in constant struggle among themselves. because of this independence of each individual.
Morganucodon oehleria “free” ancestor. ?
Seen through the prism of intelligence, mammals seem superior to other animals. But they seem inherently inferior to many others. Within the mammals themselves, the height of intellectual development, man, shows an incredible instinctual impotence compared to the most “primitive” mammal. Man, despite his youth, is in some respects a primitive compared to Morganucodon oehleri. However, the closer we are, the more familiar we are with this common ancestor that no longer exists except for ants or bees.
Because it is in the ancestor there is a tremor of the so-called “higher level” thought processes. This is emphasized Pierre Teilhard de Chardin in The Human Phenomenon (1955): “SIf a hairy quadruped seems to us, in comparison with an ant, very “animated”, truly alive, the reason is not only that with it we find ourselves zoologically in a family. In the behavior of a Cat, a Dog, a Dolphin, what adaptability! Very unexpected! What a great part is given to the joy of living and to curiosity! Gone is the instinct, like that of the Spider or the Bee, narrowly channeled and paralyzed in one function. […] Around him an “aura” of freedom, a spark of personality, begins to float. And from that side, as a result, possibilities take shape – endless and endlessly ahead. »
We are already experiencing this little freedom in Morganucodon oehleri. In any case, it is easier for us to think of it than the best bee. Of course, there is a certain shame in being traced back to our kinship with this primitive animal. But there is also something to admire: because we glimpse in him the slow evolutionary path that leads to the strengthening of the essential impulse towards intelligence, which must patiently impose itself at the expense of other important tendencies. It is clear that there is no reason to discount the value of these other tendencies, only to admire the irreducible multitude of contradictory paths taken by the creativity of life.
It is good in that direction. that’s part of contemporary research: attention to what makes each animal family unique, without worrying about hierarchy. This leveling must have favored the proliferation of research on animals closer to us; but this rebalancing of attention did not lead, far from it, to the abandonment of the “mammal” category. Mammals continue to arouse intense interest. The deepening of our knowledge of other animal families, far from causing neglect in the study of mammals or eliminating the boundaries between groups, allows more to define what creates the singularity of each life line compared to the others. .