Chapter Six

Laughter and Sex

We primates have been laughing at life and at each other for a very long time. It seems likely that it all began with a tickle in play and this legacy is still a part of our everyday lives. Laughter is heard 30 times more frequently in company than when you are on your own. In conversation, the speaker laughs more than the listener, indicating that it is a normal part of verbal communication. If you are chuckling to yourself, you probably have virtual company in your head or on the page or screen. Hearing laughter induces laughter in others. All of this play vocalisation can happen without anyone even saying, ‘Have you heard the one about the three-legged chicken?’ When you do hear that joke and laugh, you are responding to something different: incongruity. But why is resolving incongruity funny?

This question turns out to be easier to answer once we recognise what incongruity actually is. An incongruity is a mismatch between sensory data and expectation. For example:

A little girl goes into her local library to take out a book called Advice for Young Mothers. ‘Why do you want a book like that?’ asks the horrified librarian.

‘Because I collect moths,’ replies the little girl.

The mental faculty that detects incongruity is an error-detecting mechanism. This hypothesis has itself been gradually evolving over the centuries, through the humour theories of Aristotle, Hobbes and Kant amongst others, coming to fruition in our own century when three cognitive scientists called Hurley, Dennett and Adams decided not to walk into a bar, but to write a book instead. In Inside Jokes: using humour to reverse-engineer the mind, they use humour to look inside our heads. It has to be said that fMRI works better, though as we have seen, using the two together works best of all. The insight that Hurley & friends brought to the party was essentially that errors are bad and so spotting and debugging them is good. There! I’ve saved you 300 pages of dense reading.

To anyone who has ever been on the wrong end of a piece of failing computer software, it will be self-evident that having an error-detecting mechanism is a good thing. Just think of the mess that predictive text can make of a message written on a smartphone, such as this classic:

Great news — Grandma is homosexual!

Okay?

Homo hot lips

Hot tulips

I am getting fisted

Frustrated

Grandma is h o m e from h o s p i t a l

When the phone’s software fails, our own error correction circuits are tickled into action. The humorous response to incongruity is how the mind identifies cognitive bugs. It is obviously a good thing to have an error-detecting algorithm running inside your head, so it’s not hard to see why natural selection would have endowed us with this. Just to make sure that we do what is good for us, Hurley et al. contend that ‘the pleasure of mirth is an emotional reward for success in the specific task of data-integrity checking.’1 Or in other words, evolution says, ‘Do your homework, it’ll be fun!’ I’d like to offer you the alternative hypothesis that when evolution attached humour as a trigger to laughter, fun came as part of the set. It was there already. Batteries included, ready to play.

However, there is something not completely convincing about the debugging hypothesis itself and it is this. If laughter just signals debugging, why do we laugh only at frivolous errors?2 Surely, if the pleasure of laughter is a reward for successful debugging, then the more serious the error, the bigger should be the laugh. But it’s not actually like that. Make a more serious mistake, like forgetting your partner’s birthday, and neither of you will laugh at the error.

It is as though evolution has designed us a crucial piece of software that can spot errors and save lives, and then rewarded us for just playing around with it. So, could there be another, better explanation for why we find the resolution of incongruity funny only when, as Darwin observed, it is not momentously important? The answer is yes, and it’s to do with sex.

The sex hypothesis is that humour is a public display that influences courtship. It was first proposed by psychologist Geoffrey Miller,3 based on an insight that yet again we owe to Charles Darwin. In 1871, the year before Darwin published his book The Expression of the Emotions in Man and Animals, he published another ground-breaking volume called The Descent of Man, and Selection in Relation to Sex.4 It’s a curious work that is really two books in one. The first part is all about establishing that humans belong to the animal kingdom and that we’re not specially created, while the second half of the book is a comprehensive survey of all the cases Darwin could find where males and females of the same species differ from each other in secondary sexual characteristics. These are the characteristics, other than reproductive organs themselves, that distinguish the sexes. Boobs and beards in our own species for example.5 Why, Darwin wanted to know, should the sexes so often differ like this?

Darwin’s answer was that the evolution of secondary sexual characteristics can be explained by the different requirements of acquiring a mate. Natural selection will favour any characteristic that helps in courtship. Darwin called this kind of natural selection ‘sexual selection’. Geoffrey Miller reasoned that many cultural features of human behaviour, like music, art and humour, may have arisen through sexual selection because they help attract mates. One potential difficulty with Miller’s hypothesis is that artistic ability does not necessarily differ between men and women, but we shall return to this point.

The reason that we expect sexual selection to produce differences between males and females is the fundamental fact that sperm are cheap and plentiful compared to eggs. A man produces new sperm daily, but a woman is limited to the number of egg cells she was born with. This difference, and more especially the greater biological investment required for a female to gestate her offspring than for a male to sire one, has profound evolutionary consequences. It is also a fertile source of jokes:

My wife only has sex with me for a purpose. Last night she used me to time an egg. (Rodney Dangerfield)

The morning after the wedding night, the bride says, ‘You know, you’re a really lousy lover.’ The bridegroom replies, ‘How can you tell after only 30 seconds?’

While, from a female’s perspective, reproduction looks very different:

To simulate the birth experience, take one car jack, insert into rectum, pump to maximum height, and replace with a jack-hammer. And that would be a good birth. (Kathy Lette)

Females tend to be choosier than males in their selection of mates because of their greater biological investment in offspring. Dorothy Parker had a keen sense of this imbalance. She said after an abortion ‘It serves me right for putting all my eggs in one bastard.’ Parker named her canary ‘Onan’ because, like the character of that name in the Old Testament, ‘He spills his seed on the ground.’6 Only a male can afford to be so profligate.

Why do males produce millions of sperm? Because they won’t stop to ask the way.

Of course, some religions do not agree about the superfluity of sperm, as satirised by Monty Python in their song ‘Every Sperm Is Sacred’.7

Sexual selection operates in two distinct ways: through competition between members of the same sex and through mate choice between the sexes. Competition between males for access to females is very common and explains, for example, the large tusks of bull elephants and the antlers of male deer used in battles between stags during the rut. Female-female competition can occur too of course:

Joan Rivers: Besides your husband, who’s the best man you’ve ever been in bed with?

Joan Collins: Your husband.

Joan Rivers: Funny, he didn’t say the same about you.

Some say that female fashion is based upon competition between women. Groucho Marx once quipped:

‘If women dressed for men, the stores wouldn’t sell much — just an occasional sun visor.’8

Sexual selection is often driven by the choosiness of females for mates and it can lead to the evolution of extremes in males. The peacock’s tail is a good example that was originally discussed by Darwin himself. Peahens are brown, dowdy-looking birds that bear little resemblance to their richly ornamented husbands. It has been shown through experiments in a free-ranging population at Whipsnade Zoo in England that peahens prefer to mate with males who have more elaborate displays and that peahens lay more eggs for their preferred mates than for other males.9 Other studies of peafowl in Japan and Canada failed to find the same female preference,10 so it is possible that peacocks are now stuck with a trait that females no longer use to choose a mate, although peahens won’t look at a male who can’t at least shake a tail feather. Equally, it may just be another case of a general phenomenon that plagues studies of animal behaviour:

Under carefully controlled experimental circumstances, an animal will behave as it damned well pleases.

We don’t know exactly how the female preference for showy males got started in peafowl. Perhaps, in the beginning, the healthiest males were naturally bright-eyed and bushy-tailed and females recognised these first modest signs of quality and responded to them. However the female preference started, once it did so a runaway process of evolution was begun in which females who chose showy males for mates would have male offspring who inherited the secret of success with the ladies. That would then perpetuate the advantage of the female preference and lead to continuing sexual selection for more and more showy tails in peacocks.

It is important to evolution through mate choice that the cue that females use to pick the best males cannot be faked by inferior males. The cue needs to be correlated with quality as a mate. Only well-fed, disease-free peacocks can produce a really big and sexy train. It is significant to the evolution of indicators like a peacock’s train that they are costly to the male because this guarantees that the signal is genuine. Otherwise, cheats could prosper in mating and sexual selection for showy tails would cease to work. Imagine if peacocks could acquire a clip-on train, what havoc this would create for female choice.

Ornamented males with plain-looking females is a common pattern among birds, suggesting that mate choice by females is an important form of sexual selection in these species. Mate choice can be exercised in the other direction as well, by males for females:

A businessman has decided that he must finally marry and he needs to choose between three women whom he has been dating. His golf buddy suggests that he set them all a test to find which one would be the most suitable. ‘Give each of the ladies £5,000 and see what they do with it. Then decide.’ The businessman likes this idea, so that is what he does.

A month later, the two men meet again and over a round of golf the businessman tells his friend what happened. ‘Jane took the £5,000 to Bond Street, bought herself an engagement ring and proposed to me,’ he said.

‘Wow, she sounds keen! What did the others do?’

‘Elizabeth is in finance. She invested the money in the stock market and this week she sold her shares at a 50 per cent profit. She kept her profit and gave me back my £5,000.’

‘What a gal! She’s the one, right?’

‘Fiona went out and bought herself some sexy lingerie, booked us into a luxury spa hotel in the Cotswolds, told me how much she loved me, and we had the most amazing weekend.’

‘Man, these women are all keepers. So who are you gonna choose?’

‘The one with the biggest tits, of course.’

So how, you will by now be asking, can sexual selection favour humour? The answer is that humour could be a marker for intelligence that is favoured by either sex when choosing a mate. Here is how it might work. We start with the observation that, judging by its results, human evolution clearly favoured intelligence. From there, it’s a small step to the hypothesis that intelligence is a desirable trait in a mate — why would you want your children to be dumb members of a smart species? Surveys of mate preference show that women do indeed prioritise intelligence in their choice of long-term partner.11

This is no doubt why the Irish playwright George Bernard Shaw (1856–1950) was once propositioned by a famous actress with the line, ‘Think of the child with your brains and my beauty,’ to which he replied, ‘But what if he were to have your brains and my beauty?’ Shaw’s reply illustrates the next step in the argument, which is that wits and wit are correlated. Clever people make good jokes. And there you have it. A person’s capacity for humour is their peacock train — the un-fakeable evidence to any mate who will listen that you are one sexy beast who will produce clever children.

‘Hmm,’ you should be thinking to yourself at this point. ‘Here is an author cracking jokes about how clever and sexy people who crack jokes are. Could this not be a tad self-serving?’ And you would be right to ask that, so we must look at the evidence. But before we test out the idea that humour has evolved as a public display of intelligence influencing courtship, let’s caution that people are not peafowl. In peafowl, it’s the male (the peacock) who has the fancy display, but in humans both sexes participate in humour. For that reason, our hypothesis is that sexual selection operates in both directions in humans, arising from mate choice by both sexes. Whether it is equally important to both is another question that we will consider in due course.

First, we must determine whether intelligence and humour ability are inherited to any degree. If either is not heritable, they cannot evolve, and the hypothesis must be rejected right there. Next, we need to see whether humour ability is correlated with intelligence, because if it is not, the sexual selection hypothesis is holed beneath the water line. Then, we need to know whether humour ability affects mate choice and how it does so. If people see jokers as fun and good for a fling, but not reliable enough to be co-parents, for example, our hypothesis would fail. If the hypothesis passes all those tests, we must then investigate how sexual selection on humour could have started. It’s a long, long way from a tickle more than 9 million years ago to the craic of verbal humour in the pub.

The heritability of any trait such as intelligence or humour ability can be estimated by comparing twins.

Man: My wife is a twin.

Friend: Really? That could be embarrassing. How do you tell them apart?

Man: Her brother has a beard.

Some twins are identical (monozygotic) because they originate from the division of a single fertilised egg in their mother’s womb, while others are non-identical (dizygotic) because they developed from two different fertilised eggs. Dizygotic twins are genetically no more alike than ordinary siblings. The logic of the test for heritability is that if genetics influences intelligence (IQ), say, then identical twins should have more similar IQs than non-identical twins. When raised together, both kinds of twin share environmental influences with their sibling, but because monozygotic twins are genetically identical as well, they should be even more alike if genes have influence.

The relative influence of nature (genes) and nurture (environment) on IQ has been controversial for decades, but luckily, we need not get bogged down in that argument because the evidence of twin studies clearly shows that both genes and environment influence all important psychological traits, including IQ.12 There only has to be a small significant effect of genes on intelligence for selection to be able to alter it over the generations. The IQ controversy has been about how much influence genes have — but this is not a useful question because a person’s actual intelligence is determined by an interaction between their genes and their environment.13 For example, genes influence educational attainment, but good education can compensate for a poor inheritance.

An interesting question is why, if cognitive ability (intelligence) is so important to fitness, is there any genetic variation in this trait still remaining when natural selection must have been favouring the brainiest for millions of years. Surely all the good genes should have replaced all the deleterious ones by now and we should all be as clever as Albert Einstein and as witty as Dorothy Parker? The reason that this has not happened is most probably because about a thousand different genes are known to influence cognitive ability and they are not all pulling in the same direction at any one time. Trade-offs between beneficial and deleterious effects of genes are common and they preserve the genetic variation upon which natural selection may act.14 So, we’ll run out of jokes before we run out of genes that influence the intellect.

Is a person’s ability to be funny in any degree inherited? Twin studies have asked people how often they use and enjoy humour, but have not objectively evaluated the subjects’ ability to be funny. Two studies conducted in North America failed to find a genetic component to self-declared humour appreciation, but studies in the UK and Australia found that between 30–50 per cent of the variation in how much people said that they enjoyed humour was genetically influenced.15 The explanation for this difference between nations probably lies in the kind of humour that people enjoy in different cultures, because this would have influenced how they answered questions in the test. Pretty much every other twins test on personality differences has found some influence of genetics, so it’s probably safe to assume that sense of humour is no different.

The sexual selection hypothesis has now hurdled the first two fences, though only just scraping over the second one representing the heritability of humour ability. We could do with some more direct evidence on that one. Next up is the correlation between humour ability and intelligence. We are going to sail right over this challenge with the help of two studies of university students taking psychology courses.16 The ability of each student to produce humour was tested objectively and compared with their scores in tests of cognitive ability. In both studies, cleverer students were funnier and this applied to both sexes. It’s unfortunate that most psychological studies are conducted with students because they tend to be from WEIRD (Western, Educated, Industrialised, Rich, and Democratic) societies, and are not a random sample of humanity.17 However, until there is evidence to the contrary, we will accept what these studies tell us, which is that wit is a genuine indicator of wits.

Dead ahead now is the question of whether there is a mating advantage to being funny. One of the student studies mentioned looked at this with a questionnaire on frequency of intercourse and number of heterosexual sex partners, finding the predicted link between mating success and humour ability.18 This supports our hypothesis, but it’s only a correlation. With correlations, there is always the possibility that the real reason that jokers get laid more is something else that we have not taken into account, for example that they happen to be taller or better looking.

Is there more direct evidence of a causative link between humour ability and mate choice by the opposite sex? A study in France tested this connection with an experiment conducted in a number of bars (where else?). Conversations were staged between three young men in which one of them told jokes in a loud voice that could be overheard by a nearby young woman.19 After the conversation, two of the men left the bar and the remaining man went up to the young woman and asked for her phone number. Joke-tellers were twice as successful in obtaining phone numbers as non-joke tellers. While this experiment does directly support the idea that women prefer funny men, its success was surprising for two reasons. First, because the jokes themselves were so lame. It is only out of necessity I reproduce one of them here:

Two friends are talking. ‘Say, buddy, could you lend me 100 Euros?’

‘Well, you know I only have 60 on me.’

‘Ok, give me what you’ve got and you’ll only owe me 40.’

And second, because the man telling the joke always began by saying to his friends, ‘I’ve got some good jokes to tell you,’ so he was obviously not demonstrating his native wit, but his memory. Perhaps the jokes sounded better in French.

Finally, when it comes to the question of whether humour influences mate choice, we cannot ignore the fact that a Good Sense of Humour (GSOH) is a common characteristic that is both sought and offered in advertisements for partners, or at least it was before smartphones and dating apps like Tinder came along.

A guy complained to a dating agency that they had not matched him with any compatible dates. ‘Haven’t you got someone who doesn’t care what I look like, isn’t bothered that I have no sense of humour, and has a lovely big pair of boobs?’

The woman running the agency checked her database and replied, ‘Actually we do have one. But it’s you.’

Most people think they have an above-average sense of humour. Since it is statistically impossible for everyone to be above average, it just goes to show how highly we rate being funny. Nobody advertises that they want a good sense of smell or an above average sense of taste in a potential mate. Women advertising for a male partner ask for GSOH more often than men do when looking for a female partner. Men also value a sense of humour, but apparently not as much. What they really want is a woman who will find them funny.20 Because, as Virginia Woolf sardonically observed:

Women have served all these centuries as looking glasses possessing the magic and delicious power of reflecting the figure of man at twice its natural size. Without that power, the Earth would probably still be swamp and jungle.’21

It’s important to consider whether some of the apparent difference between how men and women value GSOH in a mate could be cultural rather than genetic. An online survey of mate preferences of more than 200,000 people in 53 nations found that sex differences were fairly consistent across countries. From 23 traits describing a partner, the top three for men were intelligence, good looks and humour. The top three for women were humour, intelligence and honesty.22 It is noteworthy that intelligence and humour are valued by both sexes in choosing a mate and that the difference between the sexes is only one of small degree.

We also have to recognise that national differences are not the only source of cultural influences on humour. Most nations are patriarchies in which men are in control. There is a preconceived idea that men are funnier than women.23 It is generally men who believe this but they don’t experience humour between women, who actually laugh more in conversation than men, especially when in all-female company.24

Two members of the Women’s Land Army are digging in a carrot field during World War II. One picks up a giant carrot and turns to the other. ‘’Ere, Gert, this carrot reminds me of my old man!’

‘Corr,’ says the other, ‘is he really that big?’

‘Nah, he’s that dirty.’

The rising number of successful female comedians now holding their own in a business still heavily dominated by men shows, if you ever doubted it, that female humour was previously hidden, not missing.

The sexual selection hypothesis has successfully jumped all the tests that we have put in its path and so it seems that mate choice could indeed explain why we use humour to draw attention to our sexy cognitive prowess. Sexual selection for humour ability can in theory operate for both male and female mate choice because the situation in humans is different from that in peafowl.25 A peacock’s only contribution to his offspring is his genes. He does not participate in raising his offspring as males of other bird species like the blackbird do, or indeed as is the norm in human societies. If all you have to offer a mate is a resource as abundant as sperm, you need to really shake your money-maker to get attention. But, if the sperm come with a care package for mother and offspring, this is of more value to a female and consequently males can exercise mate choice too. Men are able to exercise mate choice because they do have more to offer women than just their genes.

‘There are a number of mechanical devices which increase sexual arousal, particularly in women. Chief among these is the Mercedes-Benz 380SL convertible.’ (Steve Martin)

There is another crucial difference between the peacock’s train and the human brain. The peacock is advertising something that belongs to and is of use only to a male, but humour is advertising cognitive ability, which is manifest in females as well as males and is of value to both. With a thousand or more genes involved in cognitive ability, these cannot be confined to that tiny part of the genome on the Y chromosome that is the exclusive property of males. So, genes affecting cognitive ability are necessarily present in, and are expressed by, both sexes. The actress who propositioned George Bernard Shaw was absolutely right. If she had borne his child, whether a boy or a girl, it would have inherited a share of his intelligence and her beauty because both are determined by many genes. GBS may have been a wit, but he had some half-witted ideas about genetics.

Peacocks may be only an imperfect model of sexual selection as it applies to humour, but there is a feature common to both that we have not discussed yet.

Why didn’t the peacock cross the railroad track? Because he didn’t want to catch his train.

Humour, like a peacock’s train, can be a handicap if you get it wrong. This joke ought to be funny, but it’s a groaner, isn’t it? I’m not sure why, perhaps because there is insufficient incongruity between the set-up and the punchline, or because it’s too complicated. You can see that it’s meant to be funny, but it’s a flop. And there is the hazard of humour. Failure is as public as success. Remember that for sexual selection to work, the production of the indicator must be costly to the producer or cheats will defeat the discriminating value of the indicator. The cost of showing off your cognitive ability with humour is that you expose yourself to ridicule as well as to approval. The cost of trying to make people laugh is that you yourself might end up becoming the joke and feeling stupid.26 This hazard is inherent in humour and only the genuinely witty can avoid it. Fakes will out. People are adept at telling the difference between genuine and forced laughter, even across a language barrier.27

Let’s summarise the story so far before we move on. All young mammals play and emit play vocalisations that may have originated as an ‘all clear’ signal. This seems to have been the evolutionary origin of laughter, and may also explain why laughter is contagious, since play requires all playmates to signal their harmless intent to each other.28 Humour later became an additional trigger for laughter, inheriting the properties of pleasure, safety, spontaneity and contagiousness that are associated with the original play vocalisation. Humour is generated by the resolution of incongruity between expectation and sensory data. This is a kind of de-bugging mechanism, but that cannot be the main function of humour since it is only triggered by incongruities that are non-threatening. An alternative hypothesis that is supported by a wide range of data is that humour is a public display of cognitive ability favoured by sexual selection through mate choice.

So far so good for the sexual selection hypothesis, but what about another possible benefit of humour, the idea that ‘Laughter is the best medicine.’ Taken literally, this idea is not true. A survey of the health of 500 amateur stand-up comics, who must surely be exposed to more laughter than anyone else, found that they were actually in worse health than people of similar age and gender.29 In fact, there is good evidence, taken from comparing the lives of comedians and other actors, that comics die younger. Worse still, funnier comics die youngest of all, though why is not yet clear.30 The British comedian Tommy Cooper actually died in the middle of his show at the age of 63. None of these studies were clinical grade, double-blind trials of the kind used to test the efficacy of actual medicines, but they suggest that stand-up comedy is not the healthiest of professions, even by the low standard of performers more generally. Comedians are laughter-makers. No one to my knowledge has yet tested whether audience members live longer if they laugh more.

The phrase ‘Laughter is the best medicine’ has an evolutionary history of its own, having started in Proverbs 17 of the Bible, which in the King James version reads ‘A merry heart doeth good like a medicine.’ This more modest claim is supported by the scientific evidence, though with some qualification. Although uncontrollable laughter has physiological effects and can even render the laugher temporarily helpless, there is no evidence of physical benefits from laughter as exercise.31

In contrast, the beneficial effects of laughter on feelings of well-being and mental state are well supported.32 Not only does physical laughter cheer people up by generating endorphins, but laughter also raises the pain threshold.33 The cognitive effort involved in cracking jokes in stressful circumstances can help not only during the stressful situation itself, but also with coping with the memory of it afterwards.34

Is it possible that the beneficial effects of laughter on mental health could have contributed to its evolution in the first place? That does seem possible, though it would be additional, rather than an alternative to the role of sexual selection. Play and choice of mate between them account for so many features of laughter that health benefits alone cannot explain on their own. For example, in long-ago ancestors who had not yet evolved a sense of humour or attached this to laughter, what health benefit would detecting trivial incongruities provide? On the other hand, once humour and laughter had evolved with their associated hormonally-induced feel-good reaction, it is easy to see how the resulting beneficial effects on mental health might add to the advantage of humour. It is typical of evolution to tack one benefit onto another, and this may be what happened with health effects, although it is equally possible that these are merely fortuitous by-products.

In the story so far, we have given the biology of laughter a thorough examination and uncovered its hidden evolutionary history.

What do you call someone who does not believe in evolution?

A primate change denier.

The most important step is to realise that ‘Why did evolution make us laugh?’ is a meaningful scientific question in the first place. Once you realise that it is, it’s only a short step further to seeing that laughter is a play vocalisation with a deep evolutionary origin. Humour became a trigger for laughter much more recently, but it built on another pre-existing function of the brain: error detection. Curiously, we only laugh at trivial errors, or incongruities, because laughter is not about survival but seduction, not about defence but display. Sexual selection is the key: humour is a demonstration that you have the wits to woo.