Human moral behaviour: Why are people nice to each other?

Danial Asadolahi
14 January 2016

Above Image © ImagineGolf, iStockphoto.com

People can sometimes be mean to each other. But most of the time, they tend to be cooperative, kind, and helpful. Have you ever wondered why? Scientists who study evolutionary psychology have. They use the term “human moral behaviour” to describe people being nice to each other.

Evolutionary psychologists base their ideas on evidence gathered by researchers in the fields of paleoanthropology, primatology, and anthropology. This research points to Charles Darwin’s famous theory of evolution by natural selection as the key to understanding human moral behaviour. It helps to explain not only why people are generally nice to each other, but also why you tend to feel shock and outrage when they’re not.

Did you know? Across the animal kingdom, many species show cooperative or moral behaviours. Examples include the chimpanzee, a close genetic cousin of humans.

Evolution by natural selection

To understand evolutionary psychology, you need to understand Darwin’s theory of evolution. You may have already come across this theory at school. But here’s a quick summary in case you haven’t. Basically, the organisms (plants, animals, and microbes) that are best equipped to deal with environmental challenges are more likely to survive and reproduce. This includes characteristics that provide an organism with more opportunities to mate. So the most successful plants, animals, and microbes pass their genes on to their offspring, as well as future generations. And the genes of less successful organisms are less likely to be passed on.

This process is called natural selection. “Natural”, because the genes that make some organisms within a population more successful than others are selected for naturally. These genes may be the result of mutations. But they are not consciously chosen by the organism itself, or by something or someone else. In this context, “evolution” refers to the appearance of a new behaviour, ability, or trait as a result of natural selection.

Fast ancestors

Let’s take the ability to run as an example of evolution by natural selection in humans. Human beings are a type of ape that first appeared in Africa. Hundreds of thousands of years ago, human ancestors who lived on the African savannah survived by hunting animals and collecting plants.

What would have been an important environmental challenge to these early human ancestors? If you guessed predatory animals like lions, you would be right! If a particular early human wasn’t a very fast runner, there’s a good chance they would have easily fallen prey to a lion at a young age. As a result, they may not have survived long enough to pass their genes on to the next generation.

Meanwhile, faster humans would have had a much better chance of passing their genes, including genes associated with running ability. Slowly but surely, those genes would have spread through the human population, while genes that didn’t allow for quick running would not be selected for.

Running ability in humans probably evolved in this way. But if you’re worried that your genes aren’t perfect, keep in mind that genetics isn’t destiny. There are lots of things you can do to offset the negative effects of some genes. For example, genes that cause bad eyesight can be dealt with using glasses.

Did you know? Examples of democratic behaviour have been observed in chimpanzee societies. Without the consent of those they govern, alpha chimp males have trouble ruling.

Human morality

Moving on to human morality, I think it’s fairly obvious how natural selection would favour traits like cooperativeness, kindness, and helpfulness. For example, prehistoric humans who regularly displayed these traits would have been more likely to help one another defend against deadly predators. And they would have been more inclined to help one another find food.

In other words, these traits help an organism like you survive and reproduce. Prehistoric humans who had them would have been more likely to survive and reproduce than humans who weren’t as nice and cooperative. In time, genes associated with cooperation and compassionate tendencies spread across human populations. And genes associated aggressive and selfish tendencies became less common. Or course, these “bad” genes did not entirely disappear. In fact, in some circumstances, they may have proven useful to survival and reproduction.

If evolution by natural selection hadn’t shaped human morality, you would probably see a lot more meanness and cheating. Society would also likely be affected by a lot more seriously immoral behaviour--like murder and rape. But you wouldn’t necessarily be bothered by these issues, since you wouldn’t be genetically inclined to care very much about moral behaviour.

Thankfully, humans tend to avoid immoral behaviour. And they are usually shocked or disgusted when they see it. As a result, religious, legal, and other types of systems have been developed to punish and rehabilitate those who act immorally. And that’s the story of the evolution of humans, the ape species that achieved high levels of moral behaviour.

Learn more!

Links to text, image and PDF versions of various editions and translations of Darwin’s groundbreaking work on evolution by natural selection, first published in 1859:

Online guide to publications related to evolution and evolutionary psychology:

Scientific papers on topics related to evolutionary psychology:

Hunter-gatherer cooperation (2012)
Joseph Henrich, Nature 481
Link to summary. Registration or subscription required to view full text.

The Evolution of Religion: How cognitive by-products, adaptive learning heuristics, ritual displays, and group competition generate deep commitments to prosocial religions (2010)
S. Atran & J. Henrich, Biological Theory: Integrating Development, Evolution, and Cognition 5

Cooperation, punishment, and the evolution of human institutions (2006)
Joseph Henrich, Science 312
Link to summary. Registration or subscription required to view full text.

Why people punish defectors: weak conformist transmission can stabilize costly enforcement of norms in cooperative dilemmas (2001)
J. Henrich & Boyd, Journal of Theoretical Biology 208

Danial Asadolahi

I'm from Vancouver, B.C. and am currently working towards my doctoral degree in psychology at Adler University in Vancouver. I've been interested in science from a young age, and strongly believe that a science-based education is key to the health and happiness of human societies worldwide. My scientific interests are broad, ranging from biology and physics to the social sciences (particularly psychology, economics, and sociology). My hope as a volunteer author with Let's Talk Science is to do my best to educate young minds about the wonderful activity that is science, and help increase their scientific understanding of various phenomena.


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