Why We Laugh – Detailed Evolutionary Origins

A short text on why we laugh, what its evolutionary preceding behavior was, how it transformed to today’s laughter, and the triggers to laughter.

There are multiple theories around on why we laugh. Most are concerned with its social function. But they almost always lack a detailed description on why exactly this behavior called laughter emerged.

Here I will present to you a short and detailed theory that explains every evolutionary aspect of laughter. It will also explain why we laugh in certain situations and what makes a good joke and why it makes a good joke.

We start is with the evolutionary root of aggression and aggression deflection. This is very important as it is the root of laughter as you will see later.

When a species of animals wants to survive they must space out in the available space and land. Not all animals can live in the same spot, as there will not be enough food and diseases would spread too quickly. There are animals that live in groups, but these groups also need to separate from other groups and spread out.

Nature achieves this spreading out by an emotion called aggression. When individual animals are physically close to each other, aggression develops until a fight breaks out. This fight determines who is stronger and who has to leave. The fights can be real and dangerous or symbolic. Either way, the confrontation decides who is the stronger and who leaves.

But animals also need to come close together physically for mating, for living in groups, and while parenting. Nature had to come up with a way to defuse the natural aggression of individual animals against each other.

Let’s talk about ducks.

When two couples of ducks (each couple consisting of a male and female) are having a confrontation then it happens that one of the females threatens the other couple and swims towards them. Once this female has some distance from her male, she becomes insecure and turns around and swims back to her male while turning her head and continuing to show threatening aggression behavior towards the other couple.

Where it becomes interesting is that this turning the head and showing aggression of the female became a ritual. Female ducks also show this turning the head away from the male and showing aggression during the courtship, although there are no other ducks around. It has become part of the coutship process. The message the female duck sends is: “I am not aggressive against you, but against that other duck”.

When a female and male duck get physically close to each other, then aggression emotion comes up. By channeling that aggression to another real or imaginary duck, nature has found a way to deflect the aggression behavior and enable a male and female to get closer despite both of them feeling the aggression emotion.

Even more, it has become a bonding ritual for the ducks that is performed during the courtship process. But because it has become a ritual, it is also performed by the female duck when she does not feel strong aggression, it has become an instinct by itself.

Konrad Lorenz described this evolutionary process for ducks in his book “On Aggression”.

Let’s go from ducks to something more similar to humans: primates. When primates are aggressive to each other, they show their teeth. This threatens the other primate as strong teeth are a very powerful weapon that can hurt the other badly.

Primates don’t laugh, but humans do. There is some evidence to the contrary, but it is not comparable to humans.

The argument is now the following: laughter emerged from the showing one’s teeth threatening gesture. It has gone through a similar ritualization process as the threatening gesture of the female duck.

Laughter makes aggression go away and creates social bonding. During courtship a women often laughs at the man’s jokes. When there is need for aggresion reduction between two people, laughter emerges.

Online dating profiles are full of women writing that they are looking for a man that can make them laugh. It is not that such a man is an especially funny person, but given he is attractive to the woman, she will laugh at his jokes.

Between males, laughing serves the same purposes of aggression deflection and social bonding.

This laughing experience has found further ritualization in humans by the use of jokes.

We still can find the evolutionary root of aggression in joking. Mel Helitzer writes in his book “Comedy Writing Secrets” each joke needs a victim. It is someone who is being made fun of, someone looking stupid, someone being put down. Somewhere each joke or fun remark is against someone, even if the someone is oneself (self-deprecating humor).

This also makes sense from an evolutionary perspective. Aggression is also always against someone (else).

There is laughing and there is smiling. Both feel similar emotionally and both provide aggression reduction and social bonding. With smiling it is easier to see how it might have developed from the showing your teeth aggression expression. Is laughing a stronger version of the primary smiling behavior? Or has laughing developed first and smiling followed later? I do not know.

The argument is made by now that laughing is deflected aggression behavior, probably of showing one’s teeth. I could finish the article here. But I will add another interesting twist.


Laughing and comedy makes up a surprisingly large part of human interaction. Why so much?

It probably has to do with mate selection. Geoffrey Miller’s “The Mating Mind” is a good book on the topic.

Evolution is a constant fight against errors in the copying process of genetic code. Each time a cell divides and copies its DNA errors might occur. If there was no natural selection then each new generation of a species would have all the errors of their predecessor plus the new errors that happened when their own original cell came to life. Eventually so many errors would have accumulated that any new individual of this species would not be able to survive any more.

There are at least two processes that keep the genetic code in good condition. One such process is classical natural selection. It is known to most people: the animal with the weakest genes (most errors) simply dies or does not have children while the fitter animals procreate. This slows down error accumulation, but it still happens. Very simple life forms like bacteria can get away with it. But for more complex animals something else is needed.

This is where the distinction between male and female comes into play. Each parent has two versions of all genes. It passes along to the child one of these two versions in random fashion (actually it’s more complicated). Hopefully it passes along the version with less errors and the other parent does the same and hence a child with very good genes will emerge. This child will have a better gene quality than its parents, because it inherited the good stuff from both parents. Some siblings will not be that lucky and inhibit the bad stuff. They die.

The problem of DNA error accumulation makes it of uttermost importance to choose a mating partner with high gene quality.

As good genes cannot be observed directly, the choosing person has to rely on indicators. These indicators should be difficult to attain and hard to fake.

The beauty and healthy appearance of women is such an indicator. The height and strength of males is also one. The tail of a peacock is another example. Only the healthy and strong males will be able to expend the required energy to grow such a tail.

Geoffrey Miller argues that the human brain is also such an indicator. The brain is an extremely complicated organ and genetic mistakes can easily have devastating consequences on it performance. It is kind of an early indicator for genetic problems.

How do you test the brain of another person to see if it works? You talk to the person. And hey, if the other person can do good joking then you know they probably have many things going for them.

When choosing a mate many things are important: genetic quality, social status, health, ability to provide for the children, and many more. Genetic quality is the most important one. This is why a poor witty Casanova can have better luck with a woman than a very rich man.

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