There is a dark side to biology. For many years, I’ve been uneasy about what seemed to be a dark and unappealing side of biology. It centers on the 19th- and 20th-century models of evolution, which radiated strong images of randomness, violence, competition, and struggle. In addition, a lot of the public considered evolution an unpalatable alternative theory of biological origins. Recall the 19th-century British woman who, on hearing about evolution, famously remarked (something like),
I hope it isn’t true, but if it is, let’s trust it does not get spread around.
Running parallel to these images about animals and plants were widely held perceptions that human nature, at the core, was self-centered, individualistic and, well, just plain nasty. Are these depressing views of nature and human nature really the way things are? Is it possible the nature of evolution is essentially antagonistic to human longing for peaceful existence in the world?
This essay examines, first, the origin of some of these early ideas, and then looks at contemporary understandings of how evolution actually works. Finally, I hope to show how evolutionary processes can generate cooperative behavior, promoting peacemaking and reconciliation.
Darwin and early images of natural selection. February 12, 2009, was the bicentennial of the birth of Charles Darwin. That year was also the sesquicentennial of the publication, in 1859, of Darwin’s On the Origin of Species. Commemorative events occurred world-wide. This essay may be thought of as a local celebration of the work of that remarkable man.
Darwin’s method was to distill a myriad of observations about nature into a grand idea to explain biological change over time – evolution. He captured a key idea in the term
natural selection. Darwin apparently chose to associate the idea with
artificial selection, the common English practice of choosing the
pick of the litter to develop a new breed, particularly of pigeons and dogs. Darwin’s creative leap was to imagine that this process occurs not just in the barnyard, but throughout nature, so he called his idea natural selection.
Early perceptions of the way
evolution by natural selection worked were fixated on competition. The biologist T. H. Huxley, so-called champion of Darwin’s ideas, argued that natural selection involved vicious, relentless competition. Darwin’s contemporary, the economist Malthus, coined the term
struggle for existence to describe the grim life of workers in the British Industrial Revolution. In 1850, Alfred Lord Tennyson wrote an immortal line describing nature as being
red in tooth and claw. And a year later, the economist Herbert Spencer introduced the term
survival of the fittest. So in 1859, when Darwin’s idea of natural selection appeared, British society had a set of ideas by which to imagine – actually distort – evolution.
Then social and economic theorists used the concept of natural selection to justify cutthroat economic policies, according to which it was natural for the powerful to exploit the weak. Individualism was the supreme value while socialist tendencies were to be suppressed.1 This was Social Darwinism. Such mean-spirited perceptions of the natural world persisted for more than a hundred years, even showing up in the great 1951 movie, The African Queen, starring Humphrey Bogart and Katharine Hepburn, in which Rosie, the Methodist missionary, says to Mr. Allnutt:
Nature is what we were put into this world to rise above.
The past 150 years have generated much new evidence about the nature of evolutionary processes, beginning with Mendel’s principles of heredity in 1900, followed by population genetics shortly thereafter. In our generation, molecular genetics showed us how we share genes and cellular processes with those of many other species. There is now so much evidence about evolution beyond what Darwin knew that there is a call to retire the term
Darwinism and simply use
evolutionary biology. This will not please creationists, who like to use Darwinism in the same sentence as Marxism, Nazism and other equivalent evil
Evolution works by differential reproduction. One major conceptual change about how evolution works concerns the preoccupation with competition. A solid, central process in evolution, of course, is heritable change in a population over time. But rather than happening by
nature red in tooth and claw, it occurs quietly and subtly, in a manner not likely to be noticed by the casual observer.
This is because, if existing environmental conditions favor the reproduction of parents with genes that are somewhat different from some others, more of the genes of the former naturally pass to the next generation in their offspring. Over the generations, even this sort of mild selection results in cumulative change in the gene pool of the population, and that’s evolution. Using the lingo of the ’60s, natural selection is much more about
Make love, not war than it is about
Kill, kill, kill! But proper and pedantic biologists will prefer the technical term
differential reproduction due to relative fitness.
Randomness is good for you. Another widespread misconception about evolution is that it is just about chance. Contemporary examples of this error appear frequently in the public press. It is understandable that it may appear impossible that complicated creatures like humans can come about by pure randomness. But much about evolution is decidedly not random. But first, chance in biology should be celebrated; randomness is good for you! Genetic diversity in a species is critical. Without it, evolution cannot happen. Mutation of genes is clearly random. There is also no evidence that the type of mutation appearing is automatically biased to help a species survive. Beyond mutation, organisms generate a vast array of genetically diverse eggs and sperm, by shuffling chromosomes, exchanging pieces between chromosome pairs, and by carrying out a variety of chromosomal rearrangements: duplications, deletions, amplifications, and translocations. Recently, new high-resolution chromosome analyses revealed these changes occur at far higher rates than previously estimated. And finally, reproductive sex brings together eggs and sperm with different genetic histories, creating a novel, unique combination of genes. With respect to all this randomness, maybe Einstein had it wrong: God does play dice.
Natural selection is anything but random. Now to correct the error that evolution is only about chance. The specific parameters of the environment – temperature, sunlight, nutrients, pH – all may be critical in determining which organisms in a population will most successfully reproduce. So if people characterize evolution as a chance process, they are only half right. This is batting .500 – fine in baseball, but lousy in biology.
A useful aphorism for evolution is Generate and test – generate genetic novelty, then test out which genetic combinations work best in the current environment. Some will do better than others, leaving more offspring than others and again, that’s natural selection.
People may be offended by the role of chance in biology because of the prevalent belief that nature is under benevolent control or, as the gospel song says,
He’s got the whole world in His hands. Perhaps there is comfort in believing that God manipulates events in the biological world. All one can say is that there is no evidence for it. Biological science makes no appeal to supernatural forces to explain and understand life processes. It is like the 19th-century French artist Gustave Corbet’s comment, when asked to put angels into a picture he was painting. He responded,
I have never seen angels. Show me an angel and I will paint one.
Individualism and altruism. Another major contemporary change in the model of evolution is with the idea that selfishness is the core motivation of individuals. The 19th-century understandings of natural selection, as championed by Huxley, asserted that animals behave only to increase their own individual (selfish) chances for reproduction. For a century after Darwin, competition among individuals within a species was about the only interaction that anyone could imagine could drive evolution.
These ideas about biological competition fit comfortably with ideas of rugged individualism. Adam Smith, for instance, asserted that humans are
rational... and self-interested actors who desire wealth, avoid unnecessary labor, and...make judgments towards those ends.
In our time, British biologist Richard Dawkins’ concept of the selfish gene takes individualism down to the molecular level. And the public often interprets the
selfish gene notion as saying
we are born selfish.
This self-centered view of human behavior persists even in contemporary politics. David Brooks of the New York Times took Republicans to task for adhering to Barry Goldwater’s
highly individualistic vision of human nature, quoting him as saying,
Every man, for his individual good and for society, is responsible for his own development. Brooks thinks this view of human nature is fundamentally inaccurate and wants the GOP to correct the idea of
lone individual rationality with recognition that humans are
intensely social creatures, embedded in a social order. These examples only highlight the pervasiveness views that selfish, individualistic forms of behavior are the primary and natural means by which humans socially interact.
Darwin at an early point in his writing saw social insects as a big problem for his theory of evolution by natural selection. Worker castes of bees, ants, and termites all labor in their societal roles without ever reproducing. They feed and protect the queens, who alone pass genes on to the next generation. Such altruism made Darwin fearful that, unless he could explain this behavior, his theory of natural selection could be fatally flawed.
The rediscovery of altruism in evolution. Darwin wrote,
I use the term struggle for existence in a large and metaphoric sense, including dependence of one being on another. He was imagining that cooperative behavior within a community could be an important factor in natural selection, but he came up with no way to explain it, and neither did anyone else for nearly a century.
In biological altruism, the altruist behaves unconsciously, at some cost, to increase the reproductive fitness of the recipient of that behavior. Human altruism has all of the above characteristics, plus conscious intention.
The rediscovery of biological altruism came in the late 1960s through a young British naturalist, William Hamilton. Based on field research, he found that the more genetically related the altruist and the beneficiary are to each other, the more likely altruistic behavior will occur between them. Hamilton proposed the theory of kin selection. His insight was that individual reproductive success may be enhanced by aiding genetic relatives, increasing the chance that the individual’s genes will be passed on, indirectly through the relatives. Hamilton’s Rule, (B x r) > C, predicts that if the product of the benefit (B) to the beneficiary and the coefficient of genetic relatedness (r) of altruist and beneficiary is greater than the cost (C) of the behavior to the altruist, then kin selection altruism would evolve in a population.2 The obvious example of kin selection in animals is maternal behavior, the self-sacrificing and defensive acts of a female to benefit her offspring. The aphorism
Blood is thicker than water describes how humans intuitively behave in a manner in accord with kin selection.
One requirement for kin selection is that individuals are actually able to detect genetic relatedness. In fact, mechanisms for assessing this have been documented for many species. Whether humans can do this was an open question until 2007, when a study involving human siblings demonstrated several different types of cues used to unconsciously compute genetic relatedness.3
Shortly after the demonstration of kin selection, Robert Trivers, a colleague of Hamilton’s, discovered reciprocal altruism, behavior that helps unrelated individuals increase each other’s reproductive fitness.4 This behavior succeeds as long as there is expectation of help in return, so self-interest is still the motivation. Reciprocal altruism works especially well in small populations where members know each other and recognize who helped whom. A 2009 essay in the journal Nature said of Trivers that he
worked out the evolutionary logic of kindness.
Some well-known examples of cooperative behavior among animals include vampire bats that go out to feed and, back in the cave, regurgitate food for other bats that have been less successful in the night’s hunt; social insects, like bees, that commit suicide for the good of the group (just as do humans in war); small birds that warn of the approach of a hawk, alerting the community to danger while decreasing personal fitness by exposing the altruist to the predator; and eerkats that show similar behavior.
Researchers in the 40 years since Hamilton and Trivers have found eleven different forms of cooperative social behavior distributed across many different species.5 These social interactions can be roughly distilled into two broad categories: direct and indirect reciprocity. Direct reciprocity is
If I help you, you will help me. Indirect reciprocity is
If I help you, then somebody will help me.
A 2009 paper in Nature by a team of Harvard and Japanese evolutionary biologists found that in human communities, indirect reciprocity is a more common model of cooperation than direct reciprocity.6 One’s reputation within the community is established by helping others and how well an individual helps out is monitored by the group, establishing the degree of reciprocal behavior that is owed the individual. A dozen works were cited in this paper over the past decade about indirect reciprocity in human societies, evidence of considerable interest in this phenomenon.
A case for multilevel natural selection. Exactly how does natural selection play out in a social species? Research on this question has been lively over the past several decades. Does evolution occur only by unequal reproductive success among individuals in a population, the traditional model? This process is currently called
within-group natural selection.
Some have doubted whether altruism could evolve if within-group selection is all that is going on. It is argued that if natural selection only occurs within a population or tribe, those who don’t reciprocate altruistic acts (the cheaters) will have an evolutionary advantage over altruists. Then, any genes predisposing animals to altruism would be selected against and disappear from the population.
Recently, however, a strong case has been made for between-group selection, operating among different populations or tribes of a species. David Sloan Wilson and E. O. Wilson have laid out the arguments for a
multilevel selection theory, including both in-group and between-group selection, and showing how altruistic behavioral traits could readily evolve
for the good of the group.7 This model grants that altruistic people will not have an advantage over less upright ones within their tribe, but the more altruistic a group is, the more it will prosper in comparison to those groups whose success is diluted by the cheaters. Humans actually have ways to handle cheaters in society. A 2004 report shows that at least fifteen different human societies with behavior involving
the willingness to punish cheaters and reward those who cooperate, even at substantial individual cost.8
Humans are so complicated – look at a simple example of between-group altruism in the slime molds. These start out as single-celled amoeba that feed on soil bacteria. When they run out of bacteria, hundreds of amoebae move together, forming a multicellular slug. Each slug moves around, then morphs into a form with a base, a stalk and a fruiting body, looking like a suburban water tower. The fruiting body releases spores, which drop into the substrate and germinate into many single-cell amoebae, completing the life cycle. Cells contributing to the base and stalk never do reproduce – they
altruistically sacrifice their life to create the pedestal for the globular fruiting body. Evolution here would involve between-group selection among different slugs for finding optimal places to reproduce.
Peacemaking among primates. A zoologist observing the behavior of humans compared to other animals will call us a social species and, additionally, obligatorily gregarious. This means our survival as a species absolutely depends on our interactions with others. Our zoologist would additionally describe humans as aggressive (we harm each other) and xenophobic (making we/they distinctions). How does an obligatorily gregarious species survive with violence, anger management and paranoia issues?
The Dutch American ethologist Frans de Waal, at the Yerkes Primate Research Center at Emory University, has studied non-human primates for decades and concludes that they have two behavioral processes in common that counter aggression and re-stabilize relationships after conflict: first, tolerance, which reduces competition, and second, reconciliation, which repairs relationships after conflict. He argues that if you are a social primate, these kinds of behavior are not optional, but indispensable to evolutionary success:
Any species that combines close (social) bonds with the potential for conflict needs such conciliatory mechanisms.9
Aggressive behavior in primates has received much research attention. In contrast, relatively little was known about how primates normalize relationships after conflict. De Waal finds cooperation and peacemaking behavior among non-human primates, which balances their preoccupation with violence. De Waal claims to exercise a sober-eyed and nonromantic view of his primate subjects. He has no naïvete about the aggressiveness of primates. But he finds this violence has been exaggerated in the public eye – his work, rather, leads him to conclude that many primate species live as cooperative groups, most of the time functioning in relative harmony.
Conciliatory behaviors vary a lot among different primate species. A colony of rhesus monkeys will show a dozen cases of peacemaking over a few hours of observation. Stump-tailed monkeys reconcile within one or two minutes after a confrontation. Chimpanzees, who have good memories, take their time resolving their troubles, but exhibit a fairly sophisticated third-party mediation process.7 Chimps have been observed tearing off pieces of prey and dropping it into the hands of another chimp. But chimps also kill each other; they are paranoid about their territories, and bands of males wage organized raids (war) on neighboring tribes.
Overall, de Waal thinks chimps have little to tell us about peacemaking, but bonobos have quite a lot.10 Bonobos, which have only been studied since the 1970s,
counter the persistent belief that ancestral primates were naturally violent. Bonobo groups are female-centered and egalitarian. They carry their young around for five years and have sixty-year life spans. Bonobo populations are not xenophobic, so tolerate overlapping territories without fatalities. Most distinctively, bonobos are highly sexual and have erotic practices that might make a college student blush, Among a dozen different positive social ends for which their sexuality is deployed, bonobos use sex for reconciliation.
What is our fundamental human nature? De Waal asks,
Is human nature at the core bad, and occasionally good, or at the core good, and occasionally bad? Historically, opinions tilt toward badness as the intrinsic human nature, and attempts have been made to establish a theoretical ground for it. Social contract theory, associated with Hobbes, infers
that humans exclusively pursue only their own individual best interests.11
Some religions hold that humans are doomed by
original sin. The 1690 New England Primer taught that
In Adam's fall, we sinned all. A Wichita Eagle article detailed current beliefs of a local Protestant church, which included
that man (sic) is born with a fallen nature, and is, therefore inclined to evil…12 De Waal sees such views of human nature underlying basic tenets of Western law, economics and political science. But he rejects them as poor insights into human nature. He calls these views
veneer theories; i.e., that humans have only a thin layer of morality stretched over an amoral or immoral center. In his 1996 book Good Natured, de Waal turns the veneer model inside out, arguing that humans are by nature
good, or at least basically good, with some bad.14 Note that de Waal only observes how his research subjects behave, without attributing moral qualities (
oughts) to their behavior. But he argues that good actions, for a primate social species, are those behaviors taking others into consideration; bad behavior is self-centered. Because of de Waal’s work, the stodgy journal Science recently published an article actually entitled
Biology of the Golden Rule.
Here is his basic argument: If good actions increase reproductive fitness of these social species, and if these good behaviors are grounded in heritable factors, they have the potential to evolve like any other neurophysiological characteristic. Apparently, as far back as Aristotle and Aquinas there have been proposals that morality is anchored in the natural inclinations of our species. How did this cooperative/moral nature appear?
Huxley (sort of a Dick Cheney to Darwin’s Barack Obama) denied a connection between nature and morality. Since then, biologists have nearly managed to eliminate the view that morality comes naturally to people, although Dawkins and others currently persist in the separation of biology from morality. In a 2009 New York Times article, de Waal writes:
Darwin never felt that morality was our own invention, but was a product of evolution, a position we are now seeing grow in popularity under the influence of what we know about animal behavior, in fact, we’ve now returned to the original Darwinian position.15 De Waal argues that if his apes act
as if they were good, and if humans act as if they were good in the same way, the simplest explanation is that these behaviors have their source in our common evolutionary history. Note that he is using non-human primates as evidence that humans have inherited genetic tendencies for peacemaking from the common ancestors of all us great apes. De Waal speculates that primate species co-evolved cooperative behavior as they began to evolve into a social species, substantially to solve the aggression problem.
From what can be inferred about early human evolution in Africa, our ancestors lived as small, widely scattered, hunter-gatherer tribes. They shared resources, used teamwork, censured selfish behavior, and were fiercely egalitarian. So the circumstances of early human evolution appear to be favorable for individuals with a genetic disposition toward cooperative, altruistic behavior.
The neurobiology of cooperative behavior. If rationality were the source of good (moral) behavior, it would be associated with activity in the cerebral cortex. However, de Waal argues if rationality is the source of our altruistic behavior, humans cannot be moral at their biological core, but moral by the cultural overlay that is added by learning, by choice. On the contrary, de Waal argues that altruistic behavior has evolutionary origins in the emotions that we share with other animals. Emotions are involuntary, unconscious and non-rational but physiologically obvious, thus observable by the scientist.14 If good (moral) behavior emerges from the emotions, their source will be from deeper brain centers, such as the limbic system.
There are two key emotions that de Waal considers foundational to the development of moral goodness: empathy, experiencing another’s discomfort (I feel your pain); and sympathy, recognizing emotions in another that are not your own, yet generate an unselfish response (I can’t presume to feel your pain, but I reach out anyway). De Waal finds empathy in most of the primates he studies but notes sympathy only in the great apes. These two emotional behaviors he considers the elements upon which moral responses are made.16 In humans, these emotions appear early in life. By the first birthday, children show spontaneous sympathy. Studies of identical and fraternal twins in their second year demonstrate that empathy is heritable.17 These responses develop prior to parental instruction, so as inborn behaviors may well have had their source in the common ancestors of all primates.
What about the human future? How optimistic can we be about the human future? Well, we became who we are by evolutionary processes and these processes are open-ended. So the current edition of Homo sapiens is not necessarily
as good as it gets. We could think of ourselves as a work in progress, pilgrims on a journey. A wise biologist once suggested that Homo sapiens might be the missing link between anthropoid apes and
truly human beings. Barring nuclear or environmental holocaust, the genetic heritage of biological altruism has the capacity to evolve further and synergistically support our conscious efforts to create a more peaceable world.