Is Human Morality Shaped by Evolution?

“Any animal whatever, endowed with well-marked social instincts, . . would inevitably
acquire a moral sense or conscience, as soon as its intellectual powers had become as well, or
nearly as well developed, as in man. “

Charles Darwin
The Descent of Man (1871)

Charles Darwin’s theory of evolution has long postulated that our physical traits have evolved through natural selection, and his theories are widely accepted by both the scientific community and the general public. We have evolved eyes for seeing, legs for walking, lungs for breathing. More recently, evolutionary psychologists have made the case that behavioral and psychological traits, like physical traits, evolved by natural selection as adaptations promoting survival and reproductive success, and that these traits have become embedded in our DNA. Today evolutionary psychologists and even many lay people explain human behavior and human nature in Darwinian terms. We look to Darwin for answers to such questions as: Are men and women built for monogamy? Why do we feel guilty? Why do we gossip?

These evolved behavioral traits and emotions that are hard-wired in our brains have provided a variety of adaptive advantages. We evolved selfish traits from our ancient hominin ancestors that promoted “survival of the fittest” in a world pitting individual against individual. These selfish traits include ones that promote fraud, corruption, lust, vindictiveness, ambition, vanity and more. As we joined together into larger groups and societies, we evolved tribal instincts that have helped us to cooperate within our group and have provided adaptive advantages for both the individual and the group. These tribal instincts include empathy, altruism, and collaborative behavior toward members of our tribe, but at the same time foster xenophobic, hostile and aggressive behavior towards those outside our tribe who are different from us. We also have evolved hierarchal behavioral traits to facilitate order and prevent anarchy within the group, while we have retained some of our egalitarian traits from our hunter-gatherer days. All these behavioral traits have been inherited through natural selection to promote individual and group survival and are universal in all people in all walks of life. They constitute our human nature. As eminent Harvard biologist E. O. Wilson explains, these inherited traits have created a chimeric genotype with a mix of genes for selfish behavior and for altruistic behavior. We are all conflicted between heroism and cowardice, between truth and deception. Each of us is part saint and part sinner.

Our inherited behavioral traits include what we consider both moral and immoral behavior. Evolutionary psychologists are now asking the question: Have we inherited a moral compass to help guide our behavior? Do we have a conscience that helps us to act in the interest of others and in the best interest of the group? In short, do we have an intrinsic morality shaped by evolution?

Our morality is our conviction regarding what constitutes good acceptable (moral) behavior and what constitutes bad or unacceptable (immoral) behavior. It is our sense of what is right and what is wrong. Morality varies from culture to culture, but there is commonality among all cultures. Almost all cultures extoll the virtues of love and respect for human life, honesty, fairness, empathy, compassion, and altruism, while condemning murder, theft, dishonesty, and hypocrisy as immoral. This commonality of belief or sense of what is moral and what is immoral behavior suggests that our moral compass is the product of evolution and has become part of our human nature, embedded in our genes.

Why would we evolve such a moral compass? As Sapiens came together in large societies, they learned to cooperate and help one another because it benefited both the individual and the group. The ability to recognize behavior that is beneficial to the group and behavior destructive to the group and to have a conscience to help us make the right choices would certainly have adaptive advantages for both the individual and the group. Groups with a strong moral compass would survive over groups with a weak moral compass and pass genes for strong morality to subsequent generations. Individuals with a weak moral compass and behavior destructive to the group would be punished by the group and would be less likely to survive and pass their weak morality to the next generation. It is not difficult to see how a strong moral compass would evolve through natural selection.

But our sense of morality is not entirely innate. Morals vary dramatically across time and across cultures, and there is no doubt that contemporary culture plays an important role in determining what is considered moral and immoral behavior. Gay marriage and homosexuality are accepted in many societies but prohibited or punished in others. Subordination of women is common and varies greatly across cultures. Many societies condone polygamy while it is outlawed in most societies. Female genital mutilation is practiced and considered part of the moral code in a number of African, Middle Eastern, and Asian countries. The list goes on. Consider the words of the Declaration of Independence:

“We hold these truths to be self-evident, that all men are created equal, that they are
endowed by their Creator with certain unalienable Rights, that among these are Life,
Liberty and the pursuit of Happiness.”

At the time this was written, “all men” did not refer to all men and all women. Slavery was condoned, and women were not given equal rights and did not achieve the right to vote until the 20th century. At the time of its writing, the Declaration applied only to the elite tribe of white men in our country. This example shows that our sense of morality is often restricted to our own tribe. Our cooperation and empathy are often extended only to those in our own group who are like us — not to peoples of other races, religions and other nations. Today, through cultural influences, we have extended our tribe and interpret these words more broadly, although women and minorities are still struggling for equal opportunity.

Cultural evolution has co-evolved with biological evolution and in many ways has transcended biological evolution. Morality has evolved through both biological and cultural evolution, and while much of our morality has been shaped by biologic evolution and is embedded in our genes, moral codes are greatly influenced by cultural forces in the context of current societies. We have the advantage that cultural evolution is partly under our control, and we have the opportunity to partially shape our future morality.

Achieving a universal moral code that meets the needs of all humanity, will require that we extend our code beyond our tribe and beyond our nation to encompass the global community. We must expand the “unalienable rights” of “all men” to include peoples of all nations, all races, all sexual orientations, and all religions. We must cultivate empathy not just for our own tribe, but for all those across the world who are different than we are. We must expand our moral compass to promote the well-being of all. Our future and the future of life on our planet depend upon it.

​This blog is adapted from Bruce Brodie’s recently published book Why Are We Here? The Story of the Origin, Evolution, and Future of Life on Our Planet.

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