A ma gauche, les réductionnistes emmenés par Frans de Waal et Lynn Margulis:
Obviously, says the monkey.
Human nature simply cannot be understood in isolation from the rest of nature. This evolutionary approach is already difficult for many people to accept, but it is likely to generate even more resistance once its implications are fully grasped. After all, the idea that we descend from long-armed, hairy creatures is only half the message of evolutionary theory. The other half is continuity with all other life forms. We are animals not only in body but also in mind. This idea may prove harder to swallow.
We are so convinced that humans are the only intelligent life on earth that we search for other intelligent beings in distant galaxies. We also never seem to run out of claims about what sets us apart, even though scientific progress forces us to adjust these claims every couple of years. That is why we do not hear any more that only humans make tools, imitate each other, have culture, think ahead, are self-aware, or adopt another's point of view. It is the rare claim of human uniqueness that holds up for more than a decade.
If we look at our species without letting ourselves be blinded by the technological advances of the last few millennia, we see a creature of flesh and blood with a brain that, albeit three times larger than that of a chimpanzee, does not contain any new parts. Our intellect may be superior, but we have no basic wants or needs that cannot also be observed in our close relatives. I interact daily with chimpanzees and bonobos, which are known as anthropoids precisely because of their human-like characteristics. Like us, they strive for power, enjoy sex, want security and affection, kill over territory, and value trust and cooperation. Yes, we use cell phones and fly airplanes, but our psychological make-up remains that of a social primate.
To explain human behavior as a "mere" product of evolution, however, is often seen as insulting and a threat to morality, as if such a view would absolve us from the obligation to lead virtuous lives. The geneticist Francis Collins sees the "moral law" as proof that God exists. Conversely, I have heard people echo Dostoevsky's Ivan Karamazov, exclaiming that "If there is no God, I am free to rape my neighbor!"
Perhaps it is just me, but I am wary of anyone whose belief system is the only thing standing between them and repulsive behavior. Why not assume that our humanity, including the self-control needed to form a livable society, is built into us? Does anyone truly believe that our ancestors lacked rules of right and wrong before they had religion? Did they never assist others in need or complain about an unfair share? Human morality must be quite a bit older than religion and civilization. It may, in fact, be older than humanity itself. Other primates live in highly structured cooperative groups in which rules and inhibitions apply and mutual aid is a daily occurrence.
Even without claiming other primates as moral beings, it is not hard to recognize the pillars of morality in their behavior. These are summed up in our golden rule, which transcends the world's cultures and religions. "Do unto others as you would have them do unto you" brings together empathy (attention to the feelings of others) and reciprocity (if others follow the same rule, you will be treated well, too). Human morality could not exist without empathy and reciprocity, tendencies that have been found in our fellow primates.
After one chimpanzee has been attacked by another, for example, a bystander will go over to gently embrace the victim until he or she stops yelping. The tendency to console is so strong that Nadia Kohts, a Russian scientist who raised a juvenile chimpanzee a century ago, said that when her charge escaped to the roof of the house, there was only one way to get him down. Holding out food would not do the trick; the only way would be for her to sit down and sob, as if she were in pain. The young ape would rush down from the roof to put his arm around her. The empathy of our closest evolutionary relatives exceeds even their desire for bananas.
Reciprocity, on the other hand, is visible when chimpanzees share food specifically with those who have recently groomed them or supported them in power struggles. Sex is often part of the mix. Wild males have been observed to take great risks raiding papaya plantations, returning to share the delicious fruit with fertile females in exchange for copulation. Chimps know how to strike a deal.
Our primate relatives also exhibit pro-social tendencies and a sense of fairness. In experiments, chimpanzees voluntarily open a door to give a companion access to food, and capuchin monkeys seek rewards for others even if they themselves gain nothing from it. Perhaps helping others is self-rewarding in the same way that humans feel good doing good. In other studies, primates will happily perform a task for cucumber slices until they see others being rewarded with grapes, which taste so much better. They become agitated, throw down their measly cucumbers, and go on strike. A perfectly fine vegetable has become unpalatable! I think of their reaction whenever I hear criticism of the extravagant bonuses on Wall Street.
These primates show hints of a moral order, and yet most people still prefer to view nature as "red in tooth and claw." We never seem to doubt that there is continuity between humans and other animals with respect to negative behavior - when humans maim and kill each other, we are quick to call them "animals" - but we prefer to claim noble traits exclusively for ourselves. When it comes to the study of human nature, this is a losing strategy, however, because it excludes about half of our background. Short of appealing to divine intervention as an explanation, this more attractive half is also the product of evolution, a view now increasingly supported by animal research.
This insight hardly subtracts from human dignity. To the contrary, what could be more dignified than primates who use their natural gifts to build a humane society?
Lynn Margulis Quite well.
Ever since Bishop Wilberforce asked, in a debate with Thomas Huxley, whether it was from his grandmother or grandfather that he claimed descent from a monkey, the sufficiency of evolutionary theory to explain humanity’s spiritual and moral qualities has been in question. Then, as now, the evolution of humans was a touchy subject, and after the publication of On the Origin of Species, Darwin devoted a separate work, The Descent of Man, to untangling how evolutionary understanding could be applied to humans and their special traits.
Since his account of "descent with modification" leaned heavily on natural selection of the individual, Darwin wondered how moral behaviors - which focus on others - evolved. When lying, cheating, manipulation, greed, and other less than admirable qualities seemed to benefit those individuals who practiced them, how could their opposites evolve? Pointing out that he "who was ready to sacrifice his life . . . would often leave no offspring to inherit his noble nature," Darwin pondered how members of a tribe became endowed with moral attributes.
His simple answers still apply. One who aids his fellows commonly receives aid in return. Darwin called this a "low motive" because it is self-regarding. So-called reciprocal altruism - I’ll carry your baby if you take my son on the hunt tomorrow at dawn - is operative in species whose members are capable of recognizing each others' faces. More important is the praise we love and the blame we dread, instincts that help bind tribe members who work together. Reciprocal acts of kindness and aid underlie families, tribes, and religious groups; they ensure survival and reproduction as "naturally selected" perpetuating, living entities.
Our human sort of mutual care, along with the strong feeling of life we have in the presence of sexual partners, family, friends, colleagues, classmates, and fellow citizens (in short, in the company of meaningful others), necessitates frequent communication: symbols, language, music, teaching, learning, etc. Do these activities fundamentally distinguish us from the non-human life forms with whom we share the planet and upon whom we depend for our survival? I doubt it.
This may sound inadequate to true believers in human uniqueness, especially on religious grounds. But religion serves an obvious evolutionary function: it identifies, unifies, and preserves adherents. Admonitions to desist from the seven deadly sins inhibit behaviors that threaten group solidarity and survival. Greed, for example, privileges the individual in seasons of limited resources. Lust - the biblical coveting of the neighbor’s wife (in its male-centered perspective) - interferes with ideals for the nurture of healthy children and effective warriors. Prohibiting sloth enhances productive work intrinsic to survival and reproduction of the social unit. Anger, perhaps useful in battle, destroys family and other social relationships. Envy and pride promote individual interests above those of the larger social unit. The survival value of prohibiting sin seems obvious.
By contrast, "love thy neighbor," interpreted from an evolutionary point of view, is an algorithm for social connectedness. The touted virtues of chastity, moderation, compassion, diligence, patience, moral commitment, and humility provide touchstones for effective group action. The intellectual historian Karen Armstrong, a former nun and the author of books on Christianity, Judaism, and Islam, argues that compassion is the crucial link among the major religions. The golden rule of Jesus, Confucius, and others is that we should not do to others what we would not want them to do to us. Is this not a clear precept for the evolutionary perpetuation of specific cohesive groups in familiar habitats?
We differ from other species in that fewer rules of social behavior are communicated only by shout, groan, touch, and facial expression and more by verbal explication. But all tend to maintain and perpetuate unity of the pack, gaggle, or herd. We people share a linguistic version of the universal tendency toward socio-ecological wisdom measurable in life forms at every level. After my collaborative scientific work for over a half century to detail the genetics, microscopy, and biochemistry of cells that adhere in their lives together, I consider the neo-Darwinist overemphasis on competition among selfish individuals - who supposedly perpetuate their genes as if they were robots - to be a Victorian caricature. Disease microbes that kill all their victims perish themselves as a result of their aggression.
I disagree with neo-Darwinist zoologists who assert that the accumulation of random genetic mutations is the major source of evolutionary novelty. More important is symbiogenesis, the evolution of new species from the coming together of members of different species. Symbiogenesis is the behavioral, physiological, and genetic fusion of different kinds of being; it leads to the evolution of chimeric new ones. One example is of originally pathogenic bacteria that invaded and killed many amoebae in the University of Tennessee laboratory of Kwang Jeon in the 1970s. He selected survivors, and eventually different amoebae with new species characteristics appeared among them. These had retained 40,000 bacteria in each amoeba!
A new type of fruit fly evolved after it acquired an insect-loving bacterium that prevented it from successfully mating with its old partners. Indeed, the only documented cases of the "origin of species" in real time involve not selfish genes but "selfless" mergers of different forms. Chemical and genetic evidence suggests that even mitochondria, bodies inside all of our cells that suffocate without oxygen, came from ancient mergers, truces between oxygen-respiring bacteria and the nearly poisoned cells of other kinds of microscopic beings. The mergers, naturally selected, survived to thrive and spread across the planet.
Gifted with large brains that permit us great neurological processing power, we humans plan further into the future. We recognize more of our own kind with whom, now via global communication, we establish relationships of identity and trust. But on a crowded planet, there has always been a premium on effective togetherness. Our moral nature reflects rather than conflicts with nature.
Free will may also be nature-deep. Large single-celled forams choose from brightly colored sand grains the correct ones with which to make shells. Aware of shape and color, they make choices and reproduce their kind. Awareness in some form has been naturally selected for at least 550 million years. For me, our spirituality and moral nature help perpetuate our living communities, just as similar attributes aided previous living communities whose evolution is chronicled in the fossil record.
A ma droite, ceux qui pensent que tout de même, il y a un peu plus:
Francisco J. Ayala Only up to a point.
Evolution explains human origins. We know that humans share recent ancestors with the apes. Our lineage separates from that of the chimpanzees, our closest living relatives, six or seven million years ago. Scientists call members of this lineage "hominins." The first fossil of a hominin was discovered on the island of Java in 1894, twelve years after the death of Charles Darwin, who had predicted that such remains would eventually be found. That hominin belonged to the species Homo erectus and lived more than a million years ago.
Over the past century, thousands of other hominin fossils have been discovered. The oldest of these belong to species quite different from modern humans, classified with exotic names that usually refer to where they were unearthed. Sahelanthropus tchadensis, found in Chad in Central Africa, lived between six and seven million years ago. Australopithecus afarensis, found in the Afar region of East Africa, lived between three and four million years ago. And Homo heidelbergensis, first found in Germany, lived between 500,000 and one million years ago.
For several million years, hominins had a small brain, similar to that of a chimpanzee and weighing about one pound. Brain size started to increase about two million years ago, with the species Homo habilis, the first of the hominins to make stone tools. It seems likely that smarter individuals with somewhat larger brains would have been able to make better tools, which was advantageous for hunting, fighting, and so on. As a result, smarter individuals would have left behind more descendants. Gradually, over the last two million years, brain size tripled, reaching about three pounds in the average modern human.
Evolution also allows us to trace the origin and migration of human populations. Modern humans evolved in tropical and subtropical Africa about 150,000 years ago. They colonized much of Africa and parts of Asia and Europe starting about 100,000 years ago, and America about 15,000 years ago. As one would expect from so recent a diaspora (recent, that is, on the evolutionary scale), humans from different parts of the world are genetically quite similar, despite their conspicuous differences in skin color, body configuration, hair, and other traits that help us to distinguish people from different parts of the world.
Over the past decade, evolutionary geneticists have started to decipher the genomes of humans and chimps. Surprisingly, in the genome regions shared by the two species, nearly 99 percent of the DNA is identical. But we also have discovered distinctive human features. Genes active in the development of the brain, for instance, have changed more in the human lineage than in the chimp lineage, and so has the gene called FOXP2, which relates to speech. In fact, researchers have identified 585 genes that have evolved faster in humans than in chimps. But there is still much that we do not know about what makes us so different from apes. Fortunately, we have been searching in earnest only for a decade, and discoveries will continue to accumulate.
Evolutionary neurobiology has made similar advances. We now know a great deal about which parts of the brain have become more differentiated in humans than in apes, and what functions they play in memory, speech, hand articulation, and so on. Much has been learned as well about how light, sound, temperature, resistance, and other impressions are transmitted to the brain by our sense organs. Still, despite all this progress, the field remains in its infancy. Those questions that matter the most to us remain shrouded in mystery: how physical phenomena (the chemical and electric signals by which neurons communicate) become feelings, sensations, concepts, and all the other elements of consciousness, and how the mind, a reality whose properties include free will and self-awareness, emerges from the diversity of these experiences.
Humans also have opened up a new mode of evolution: adaptation by technological manipulation and culture. We have developed the capacity to modify hostile environments according to the needs of our genes. The discovery of fire and the fabrication of clothing and shelter have allowed us to spread from the warm tropical and subtropical regions of the Old World, to which we are biologically adapted, to most of the Earth. Humans did not wait until genes evolved that would provide anatomical protection against cold temperatures by means of fur or hair. Nor have we bided our time in expectation of wings or gills: we have conquered the air and seas with artfully designed contrivances. It is the human brain (or rather, the human mind) that has made humankind the most successful - by most meaningful standards - of living species.
But culture includes much more than adaptation to the environment and much more than science and technology. Culture includes art and literature; history and political organizations; economic and legal systems; philosophy, ethics, and religion. These all-important components of human nature transcend evolutionary biology and every other science. Science has nothing decisive to say about values, whether economic, aesthetic, or moral; nothing to say about the meaning of life and its purpose; and nothing to say about religious beliefs - except, of course, in those cases when these values and activities transcend their proper scope and make demonstrably false assertions about the natural world.
Science is a way of knowing, but it is not the only way. Evolution tells us much, but certainly not everything, about human experience and the human predicament. In The Myth of Sisyphus, Albert Camus asserted that we learn more about ourselves and the world from a relaxed evening gazing at the starry heavens and taking in the scent of grass than from science's reductive ways. This may be literary exaggeration, but there can be no doubt that we learn about human nature by reading Shakespeare’s King Lear, contemplating the self-portraits of Rembrandt, and listening to Tchaikovsky's Symphonie Pathétique. We humans judge our actions toward others according to systems of morality, and we derive meaning and purpose from religious beliefs. Evolution may explain our capacity to hold these principles and beliefs, but it does not explain the principles and beliefs themselves.
Eva Jablonka Yes, but...
we have to qualify what we mean by "human nature," by "explain," and by "evolution."
If, like Aristotle, we see "human nature" as something that depends on a basic animal nature, which in turn depends on a nature that is common to all living things, then the answer to the question is long and complicated. It has to include the evolution of the goal-directed, teleological systems underlying the origin of life and the acquisition of a mentality that endows every animal with a will, as well as the evolution of the unique aspects of the human mind. An answer would amount to re-writing Aristotle's De Anima using a 21st-century evolutionary framework.
But I think that the question being asked is a more modest one, highlighting the uniqueness of human nature as compared, for example, with the nature of our evolutionarily close relative, the chimpanzee. Many people are ready to accept that evolution explains chimpanzee nature, but not that it explains human nature. They assume that at some definite point in evolutionary history, God intervened and endowed the human lineage with something that has set humankind apart from all other animals. So let us consider these more limited questions: Is there a line of demarcation between humans and chimpanzees that makes humans very different? And can we explain human nature as a product of an evolutionary process, without miracles? I believe that the answer to both questions is "yes."
Much has been written about how humans are unique or special, but I favor the philosopher Ernst Cassirer's views on the matter. He maintained that what sets us apart is symbolic systems, most notably, our capacity to think and communicate using language. This, he argued, is the foundation of our rationality and religiosity and for creating long-term goals and abstract concepts like justice and truth, which organize human psychology and social life. Cassirer is right, I believe - but none of this changes the fact that our capacity to use symbols is a product of evolution. Describing the evolution of this capacity is an incredibly difficult task, because it has complex and multiple social, cognitive, and emotional bases. But during the last fifteen years great progress has been made in understanding it, especially with regard to our linguistic capacity. Although we are only at the beginning of this great intellectual journey, the framework for explaining the origins and evolution of symbolic systems is now in place.
At this point I also must qualify what I mean by "explain," in particular, how an evolutionary account can be said to be explanatory. If we can describe the biological basis for the appearance of a new trait in a population, describe how and why it spreads, and how, over time, it becomes increasingly more sophisticated, we may claim to have provided an evolutionary explanation of this trait. Evolutionary biologists recognize that at present there are only partial evolutionary descriptions of most complex behavioral traits. Evolution explains cooperation among ants, for instance, but we are still far from being able to give a full causal account of how cooperation is instantiated in the biology of ants and of how every aspect of such cooperation has evolved. The situation is similar but even more difficult with respect to the human ability to use language and other symbols. But the question is tractable and answerable within an evolutionary framework.
Here I must qualify yet another term, "evolution." The evolutionary framework that we need to use in this case is much wider than the one to which we are accustomed. The great evolutionary biologist Theodosius Dobzhansky famously defined evolution as "change in the genetic constitution of populations over time," but this definition is too narrow and, therefore, misleading. We have to think about more than genes. My colleague Marion Lamb and I have suggested that evolution should be redefined as the "set of processes that lead to changes in the nature and frequency of heritable types in populations over time." Heritable types include: genotypes, types of transmissible epigenetic (that is, developmentally acquired) variations, types of socially learned animal behavior, and types of symbol-based transmitted information.
With humans, the transmission of information via symbols has resulted in a very rich cultural evolution. This transmission is of major importance not only for our cultural history but also for our genetic evolution. Under the appropriate ecological and social conditions, even a crude ability to communicate using symbols, similar to that seen in trained chimpanzees, can trigger greatly accelerated genetic evolution of the capacity to use symbolic systems. This, in turn, will lead to more elaborate symbol-based cultural evolution, which will favor further genetic changes, and so on. Recognizing this positive feedback loop between genetic and cultural evolution may help us to understand how human language evolved and how other cognitive and emotional features specific to humans - artistic ability, rationality, religiosity - emerged and became consolidated during our evolutionary history.
The original question therefore needs to be rephrased in a clumsier but less ambiguous way: Can an expanded evolutionary framework account for the specifically human features that set us apart from chimpanzees and that most of us recognize as constituting human nature? The answer is "yes." Indeed, I believe that we can answer this question affirmatively even if we are committed to the more ambitious Aristotelian concept of human nature, which includes not only the nature of much simpler animals endowed with wills but the nature of life itself. There is historical continuity among the different "natures" that culminate in human nature. Giving a fuller account of the continuous evolution of these goal-directed systems is one of the great scientific challenges of this century.
Ne manque plus que l'hystérique Norberg.
