The best books on Evolutionary Psychology

We’re going to talk about five of the best evolutionary psychology books. Shall we open our discussion by defining our terms? Could you just give us a potted definition of what ‘evolutionary psychology’ means?

Psychology is often a lot of very separate pieces of experimental work about how a mind does this or that. I think evolutionary psychology is necessarily the theory that’s got to underpin all that, because for the bits of our mind with lots of specialized mechanisms to have evolved, they must have given our ancestors some benefit. Evolutionary psychology is very good at proposing hypotheses for how humans might behave on a large basis and testing those; and also for explaining some of the narrower questions, why there are particular quirks in our brain, or why we behave in a particular way.

What drew you personally, to the field?

I had a slightly strange route in. I was always interested in different subjects. I used to go to different lectures, I used to go to maths lectures and anthropology lectures, and biology lectures, and so on. I studied physics as an undergraduate at Cambridge, and physics was absolutely fantastic. I really enjoyed it. But quite a lot of it was sewn up before I was born. And the questions that were left were either incredibly hard—too hard—or very detailed. I used to wonder what it would have been like to be alive when Newton was alive, or Galileo was alive and things were radically changing. Psychology is at that position. It’s just as messy as I imagined physics was in the past, with different experiments and theories being thrown out all over the place.

And I think that, coupled with this evolutionary slant, which I think can really pull together some of these bits of social psychology, it just seems like the most fascinating bit of science that’s going on at the moment. I actually did my PhD in mathematical models of evolutionary biology. I worked for a bit in a bank, and then spent three years sitting in a room in the countryside, reading lots and learning lots and talking to people and sort of getting into it. And that’s how it all started for me.

Shall we talk about the David Buss book first, given that it gives an overview of the field? Evolutionary Psychology was first published in 1998, when the publisher described it as an introduction to “a revolutionary new science, a true synthesis of modern principles of psychology and evolutionary biology.”

There are a number of textbooks on evolutionary psychology now. In my opinion, this is the best—I suppose different people have different preferences. In some ways, I included it as a correction to some of the bias in my list, which is obviously jumping to the bits of evolutionary psychology that excite me most personally.

Whilst it’s a textbook, I don’t think there’s any reason you can’t sit down and curl up with it. It’s very well written. It covers the whole gamut of things—from really quirky bits that maybe aren’t dramatically important, like the theory of why we perceive heights to be greater when we’re on top looking down (it’s easier to slip going down than coming up)— to more obvious things, like: why are we more frightened of snakes than cars? Cars kill a lot more people, but they weren’t around when we were learning to be afraid of things.

David Buss is really good on the mating bits. So there are two really obvious things that can affect the success of your genes above all else: not dying, and having children. David Buss’s research field is all about the mating selection stuff. So it’s very good on that.

A lot of evolutionary psychology is quite new, and there are a lot of alternative theories for things. He’s very good not just at giving an answer in the way of a physics textbook, ‘Here’s the answer and here’s how to apply the answer.’ Instead it’s, ‘Here are some experimental results, and here are four different ways of trying to explain those experimental results. What differentiates those theories, and how you would test them?’

“Language is something that we’ve evolved very specialist brain mechanisms for: why? ”

Language is a really good example. We’ll look at one of Steven Pinker’s books in a minute, but language is something that we’ve evolved very specialist brain mechanisms for: why? Is it to communicate about facts? Or is it gossip about other people a social thing? Or in some way is it to impress mates? Do more eloquent people get better mates? And, if my wife fell in love with me because I’m more eloquent, why on earth would she have done that? Might it be some combination? Maybe we started evolving language to communicate information—to show that we’re trustworthy—and then once you’ve got that in place, it became useful for gossiping, and then we become more specialized for gossiping.

It’s a great book that just covers everything. I’ve enjoyed reading it and it points you in different directions.

Your next evolutionary psychology book recommendation is Martin Daly and Margo Wilson’s Homicide. This looks at the possible motives for murder as a product of the process of evolution. Is that a fair way to summarise it?

Yes. And when murder is more likely to happen. When it was recommended to me, I read it and thought it was fantastic. I thought it must be quite obscure, so I was almost disappointed to find that lots of evolutionary psychologists love this book.

Homicide is really interesting from an experimental perspective, because the data is so good. You can argue about whether somebody is abused or whether somebody is angry, or whether somebody is lying to you. But when you’ve got a murder, you’ve got a body; this definitely happened. And the police have got an incentive to find out who did it. So you’ve got really, really good data.

It’s clearly evolutionarily important, because if you’re murdered, you’re not having any further children and you’re not looking after your existing children. So when we look at much earlier stages—what makes you angry or, who you fancy, or whatever, it’s not necessarily clear that they lead directly to behaviours that influence your gene success. Murder really does do that. And that allows them to test lots of hypotheses of evolutionary psychology.

Step-parents are more likely to kill their children than natural parents. That’s something you might think is obvious—if you’ve read the Grimm Fairy Tales, there’s always an evil stepmother. But I think it was Daly and Wilson who first actually collected the data, and proved that this was so. When you’ve got natural children, they share half your genes. When you’re a stepparent, they’re absorbing your partner’s energy, which they could be putting into your own natural children.

It’s all quite horrible stuff—you’re more likely to kill very young children, for example. But if you stripped away what everybody says about morality and how they would behave, how they care about their stepchildren, it’s a little bit like what you’d expect. Lions, when they take over a pride, kill the cubs. It happens to a much, much lesser extent in humans. But it’s still measurable. It’s the young cubs that get killed, and they get killed by stepparents. The data allows us to ask questions: Why do men kill more than women? When do they kill more? Under what circumstances? Is it rich people or poor people? And what are they killing for? It’s generally not to get rich. It’s often to do with new partners, relationships, and so on.

It’s at once a horrible book and an interesting one. There are these questions, and they’re very hard to answer, I think because people will always lie about these things. And it’s so careful, the care they take over their data, their care about comparing the theories, it’s breathtaking. And deserves to be popular.

Fascinating. In terms of understanding homicide as a psychological phenomenon, this is not to suggest that murderers are actually making evolutionary calculations in an explicit way, right?

Right. I don’t think people are ever aware of it. They wouldn’t say, ‘I’m going to kill him because he’s my cousin two steps removed, and therefore less valuable to me than my brother.’ Your brain causes you to do things, but doesn’t always give you direct access for why you do these things.

You mentioned Steven Pinker’s The Language Instinct, so let’s move onto that next. This is a book I read while studying experimental psychology as an undergraduate and I have such fond memories of it, because unlike so many set texts this was not at all a chore to read. It’s so interesting, so very readable. Why do you like it so much?

It’s partly the fact it’s so beautifully written. It came out in 1994—I’d just become a teenager then, and was getting into all sorts of popular science, from Richard Dawkins to Stephen Hawking. Steven Pinker was one of those writers, although it’s hard to know if it had an influence on me later.

I’m not a linguist so it may be that some of the content isn’t as current as it was. The version I have now was published in 2007, and in it Pinker says things hadn’t changed too much. That’s consistent with what Buss said about Pinker’s theories still being current. But a bit of a warning there.

“It wasn’t obvious that language evolved, because languages look so very different. But he goes through the underlying structure and it’s very similar”

The types of arguments that you’ve got to make in evolutionary psychology, Steven Pinker made them and made them brilliantly. You’ve got to break down people’s intuition that they already know how they do what they do—use language in his case—and they already know what it’s for, and how it works. People think, ‘I don’t need to be told why I talk. I already know: I talk to tell you stuff, I talk to get things I want…’ You’ve got to break that down first.

Because, as with murderous motivations, we aren’t always conscious of the base urge.

People have these incorrect intuitions for a reason, which is of interest in itself. And Pinker is well aware of this. He’s got to argue something that we wouldn’t have to now: that the ability to communicate through language is something that was subject to evolution in the first place. It’s not just a consequence of having huge brains, that your brain gets to a certain size and you will spontaneously start speaking. He’s got to explain that there’s a module, something quite specific.

So he goes through the localisation of the brain, how it develops in children. How specific gene mutations cause specific problems in language. All of which point to the idea that the mechanism for language evolved. Individual languages not so much; there are people who speak Spanish, Chinese, and English. Maybe that’s why it wasn’t obvious that language evolved, because they look so very different, but he goes through the underlying structure and it’s very similar. They all have grammars, the grammars achieve the same things. And this deals with a question that maybe we’ve moved on from: that learning and innateness aren’t opposites. You need some innate mechanism to do the learning. He’s very, very good at explaining these things. They’re the building blocks, the things you have to get over before you can do evolutionary psychology.

“There’s something else that’s unusual about humans that we don’t often talk about: we’re the only animals that can kill at a distance”

You’ve got to remember that words are a way of changing what other people do. If I spoke, but no one else changed what they did as a result of me saying them, I would never have evolved language. And that makes another pressure: I learn to say things, but others have also got to evolve to respond to that, because if everybody just did what I told them to do all the time, then fantastic for me—but clearly not so good for their genes. So that creates a sort of arms race, and maybe that explains why there’s such a gulf between us and other animals. Once you start on that race, things proceed very fast.

So it’s a wonderful book, both for the way it’s written, for the details, and for offering a background to evolutionary psychology.

Can we just briefly hover over that point about learning and innateness, this being quite central to the field of evolutionary psychology. To put it in simple terms, could we picture this as software vs. hardware? Is that a good analogy?

I think that’s fair. Why am I hesitating? Some people have taken the computer analogy so far it’s become a bit unpopular. When you put it in computer terms, people accept all these other things that we can add on to that analogy. But I think at that surface level, yes, the hardware/software distinction makes sense.

Got it. Now, I’m very intrigued about your fourth evolutionary psychology book recommendation. This is Death from a Distance and the Birth of a Humane Universe by Paul Bingham and Joanne Souza. Could you give us an overview of the argument this book is making?

This will be a slightly controversial book. I think we all know that human minds are very unusual. We moralise. We communicate through language in sophisticated ways. What’s obviously unique about humans are our brains and our social environment. But there’s something else that’s unusual about humans that we don’t often talk about: we’re the only animals that can kill at a distance. Because we can throw objects. We use spears and bows and arrows and—now—guns. But we started off throwing rocks. If you give a chimp a rock to throw, he’s going to miss the target most of the time, he’s terrible at it. But humans, fairly consistently, can throw hard and at a distance. It would be an enormous coincidence if the same animal that could kill at a distance was the same animal that had this weird social environment and weird brainpower. Lots of people have had a go at trying to connect the two.

Often they’ve clearly been wrong from an evolutionary perspective. Warfare is the big one. People say, oh well, you need a social environment to make soldiers march and don’t hang around the back, so you need morals for welfare, and killing is to do with welfare, so the two must go together somehow. This doesn’t make sense until you’ve got a large society and enough territory to have big wars. You’re putting the cart before the horse. What Bingham realised—and it was Bingham first, in a paper—was that when you can kill at a distance, this dramatically lowers the cost of punishing other people.

“Imagine I’m a chimp, and some other chimp or even several other chimps decide I ought to be punished”

So imagine I’m a chimp, and I do something wrong, and some other chimp or even several other chimps decide I ought to be punished. Because they can’t kill at a distance, they’ve got to come close to me, and while they’re trying to kill me I’m trying to kill them back. There’s a 50/50 chance. Or, the biggest chimp will win. The morality doesn’t matter, and coalition doesn’t. So it’s hard to punish malefactors. In humans it’s different. If you and I are throwing rocks at each other, and let’s say it takes on average five minutes of rock-throwing for one of us to kill the other, it’s still 50/50. Nothing to do with morality; whoever is better at throwing is going to win. But if I come back with four friends, and we’ve all created a social connection and believe that you ought to be killed and we’re all throwing rocks, we’ll be throwing rocks at five times the pace, and we can all engage in the fight at once. It’s not like physical fighting where we have to be close and within your reach. So it’s only going to take one minute before we kill you, and there’s only a one-in-five chance that one of us will get killed.

This is known as Lanchester’s square law. It was discovered in the First World War. It’s about the use of bullets, but it applies more broadly and means that the cost of punishing people, when you are in agreement that someone should be punished, are dramatically lower for humans than for other animals. And if the costs are lower, it’s more likely to evolve. Other academics have done some of the numerical simulations and, again, show what he predicted from that basic premise. So that’s the central idea.

And of course, once you can gang up on people and punish them, all sorts of things become possible. If you start to trust people—because there’s this ultimate punishment—things like language become a lot more plausible, because you’ve got a reason to tell the truth. People can punish you if you don’t. If you look at animals, most animals, when they’re in groups they’re quite well connected. Wolves, chimps… there are odd exceptions, but mostly they’re groups of kin. In humans, that’s not how tribes work. And it’s not the way companies work.

This is a fantastic book. It’s a labour of love for him and Souza. They’ve gone across all sorts of different disciplines, looking at the dates that people started evolving to throw, which you can measure. And when we started being able to speak—there are changes in the bones of the throat, which they can time quite well.

But it’s still controversial.

Yes.  For example, Herb Gintis has suggested that Bingham and Souza underplay the importance of child-rearing, the role of culture and the invention of fire in their analysis.

We’ve also had Suzana Herculano-Houzel on our site, who pointed to cooking as the key turning point in human evolutionary history.

I think you can probably connect the different things. As I was hinting with Buss, we might have evolved language for one really important reason—communicating or telling people where the prey were—then once you’ve got these language skills, they come in useful for sweet talk and other more specialised things.

In this case, it may be that coalitional punishment—the thing that Bingham and Souza describe so brilliantly—first made co-operation in non-family groups possible.  Once you’ve got that, it makes speech more useful—because you can trust people, or it makes different patterns of child-rearing possible.  These, in turn, lead to whole new evolutionary pressures which change us in some other way and those changes introduce further pressures which we adapt to and so on.  Then, at the end of the chain, when you have modern humans, you have to pick apart a whole cascade of different pressures and adaptations which have formed us.  I don’t read Bingham and Souza as being closed to this.  They’ve shown you can explain an awful lot—an astonishing amount—just by looking at the dynamics of group punishment—but I don’t think they believe that’s the end of the story.

“If you’re frightened of controversy, evolutionary psychology is not the subject you should be studying”

It feels to me like this argument is a little more heated than the debates around language, because it’s more nuanced. But I didn’t hesitate to include a controversial book because I think much of evolutionary psychology is. It’s not like studying 19th century physics; my physics lecturer told me, ‘this is how water pressure works and we know it is because we’ve known about it for 200 years and tested it.’ This is a new discipline, and by nature that means its got lots of theories. Over time they’ll be weeded down and we’ll have more confidence.

The second reason is, you can’t rerun what happened tens of thousands of years ago. You’re left with bones, when you’re lucky. This is before people wrote history or poetry, you’ve no written records. A lot is trying to work out the most plausible story, then looking for evidence in the fossil record or in genes, or in the localisation of things in the brain that would falsify the theory. You can’t do what physicists do, which is rerun the experiment 5,000 times with slightly different conditions.

So, if you’re altogether frightened of controversy, evolutionary psychology is not the subject you should be studying. It’s exciting that way.

But for exactly the reasons you’ve just outlined—that we’re attempting to extrapolate backwards, to figure out how we got here, and can’t go back in time to find out if your theories are correct—doesn’t it ever feel frustrating?

Yes. I think it does. This is going to sound very abstract, but when I was a physicist, one of the things that frustrated me was that, as a child, I’d imagined you’d study physics and learn how the universe is. And actually science is never like that. It’s always getting closer and closer approximations to the truth. It’s adding an extra term to the series, a mathematical series. The real truth is probably something that humans can’t comprehend very well.  So I think science as an endeavour, once you get deep enough into it, is always frustrating.

If you’re a philosopher, you can write something down and genuinely believe—at least you could have done, several thousand years ago—that you have got to the absolute truth about how the world is. You’ll be completely mistaken. Philosophers, I think, don’t get very far. I think science is the better way of coming to truth, but it always leaves you frustrated at the end. You come to the edge of the field and see there’s something you can’t understand, something you can’t test, or a time when you know you wouldn’t even know what an answer looks like.

I find that very moving, somehow. And maybe it leads us to our final book, which deals with one of these notoriously difficult questions, and an area of science that has historically shared a lot of ground with philosophy. This is The Illusion of Conscious Will by David Wegner. How does the free will debate tie into evolutionary psychology?

There is a philosophical conception of free will, but here’s what most of us mean by it: I’m about to decide to pick up this pencil, I reach forward, I pick up the pencil, I freely chose to do that.

The Illusion of Conscious Will is ostensibly a social psychology book, as opposed to an evolutionary psychology book. Wegner was at Harvard, and is one of the greatest ever psychologists. He argues that we are usually mistaken about this impression of conscious will; we usually infer an intention to do something from our actions, rather than from actually being able to consciously make something happen.

He pulls together a lot of evidence. You’ll know about the old cognitive dissonance experiments—that when you get paid for doing something, it changes why you thought you did something.

Right, it’s like we edit our memories, inserting or remembering different motivations to what we recorded at the time.

But there are loads of these experiments. There are split-brain experiments; in the past, epileptics sometimes have the corpus callosum chopped.  The corpus callosum is a bundle of nerve fibres that connects the left and right hemispheres of the brain.  After the operation, the two halves of the brain can’t communicate as freely as yours and mine can. Your right half of the brain tends to control your left visual field, your left arm, and vice versa. And most of the generation of language takes place in the left brain. So if you do something with your left brain, using your right side, it’s easy to explain why you did it. But with these people who’ve had the corpus callossum cut, you can show things to the left side of their field of vision, and get them to respond to it with the same side of their body, then explain why they did it, they’ll invent explanations which seem entirely plausible, but are obviously wrong.

“That’s what we’re doing much of the time—coming up with externally plausible explanations for why we do what we do”

In the most famous example, scientists showed a picture of a snow scene to the left visual field—so, right brain—and a chicken’s claw to the right visual field.  Then the patient had to choose a picture to go with the scenes. One on each side.  The right half of the brain—so, left arm choosing from pictures in the left field—chose a shovel, which makes sense to go with the snow scene.  But the patient now has to explain why they chose the shovel. This is done with the left brain, which saw a chicken’s claw and now the shovel. Does it just admit it’s flummoxed? Not at all. The patients confidently explain that you need a shovel to clean out the chicken shed. We can see that’s really odd because of the experimental set-up. But that’s what we’re doing much of the time—coming up with externally plausible explanations for why we do what we do that don’t necessarily have much to do with why we really do what we do.

There are dozens and dozens of experiments, and mostly they’ve been left isolated. There’s cognitive dissonance stuff, self-perception stuff, all this left-brain interpretive stuff. Then there are some slightly more fanciful findings from hypnotism and so on, and he pulls them together. I think that this really hammers home that idea that the order of events isn’t ‘I consciously willed to do something, and then I did it.’ It’s much more often: I did something, I inferred why I did it, I created a coherent explanation for it.

After the fact. This is a bit like what we were saying about whether the true motives for murder are explicitly understood by the murderer.

This is really important for evolutionary psychologists to know, for two reasons. Firstly, I think evolutionary psychologists sometimes cut a corner. For example, looking at mating strategies, they might interview 1,000 men and show them pairs of pictures and say: ‘which of these images do you prefer?’ Or, they might interview 1,000 women and say: ‘Would you be willing to have an affair or not?’ Then they’ll infer differences. Which is all very sensible if what they say, and what they are aware of, directly influences what they would actually do. Because it’s the doing that’s important—actually having sex and producing children, not saying who you would be more attracted to.

If what we are now saying is that what we genuinely believe is inferred more from the outside in, you would expect people’s answers to tend towards what they think culture expects them to say. You might expect them to be just fundamentally mistaken, often, and you’re starting to completely blur the thing that leads to evolutionary consequences. I think that happens a lot. Reading The Illusion of Conscious Will would stamp out a lot of that.

The second reason is that it sets up an enormous question for evolutionary psychologists. Most of what’s studied are the obvious questions: When will you kill somebody? When will you feud over something? What will your mating strategies be? They’re sort of obvious, because biologists have already studied them in animals. A lot of it is really saying: how do these theories apply to humans?

That’s why Daly and Wilson’s book is so great. We can run the stats and say, oh, actually, it looks remarkably similar in many ways. But here’s the question: if we’ve only got the illusion of conscious will, why do we have that illusion? I’m not sure Wegner’s answers are really coherent. It’s still a big question.

One of the proposed answers is that it helps us take responsibility for our actions and gives us more self-confidence, because we see we’re having an effect on things. But it doesn’t make sense. If having self-confidence was a good thing, why not just have a module that tells you to be self-confident? It’d be crazy to have all this complexity concocting a whole other story just to convince yourself of something that could be done very simply. The illusion clearly requires a lot of specialised brainpower, so it’s doing something for us. The fact we don’t know what that is makes it the most fascinating of all questions, I think. That’s why I included it here. It has to have an evolutionary answer.

It’s so intriguing. Finally, let’s discuss your own book, Beyond Bad: How Obsolete Morals are Holding us Back.

It’s on the evolution of morality. A bit like language, it’s one of those things where you’d say it seems really odd to say it evolved.In the same way that you’ve got Spanish speakers and Chinese speakers and English speakers, you have people who are Utilitarians, you’ve got duty ethics people, you’ve got people who say their morals come from religion. You’ve got people who think abortion is murder, and those who think it’s a right. But the mechanism for holding morals, and for acting upon them, and for judging people, can have and does seem to have evolved.

Going back to the Bingham book: we punish people who step out of line. So it’s very important that you don’t do things which cause other people to punish you, and that you choose the right side to be on when you’re ganging up with your rocks to punish someone else. So we know that there will have been pressure to behave morally, in the way other people think of it. We’ve probably known for a while—philosophically at least—that the types of moral truths that most people believe in can’t, in a scientific sense, be true or false. They don’t seem to behave in that way.

There are, I suppose, there are a couple of issues. The first is: does being mistaken about morality actually harm us? Our mechanisms for holding morals happened long before Utilitarianism, or any of the modern religions. Tens of thousands of years ago, as did language. Having language is still a good thing in modern society. Having a mechanism for holding morality we might think, on balance, there are some good things about it. But there might be some quirks. I argue there are some quirks in morality, that actually make life a bit harder. It’s something that caused you to bond into groups, when you lived in tribes. That’s not so helpful in modern cities, that we’re all bunched into political groups, or racial groups, or so on.

Secondly, if you’re seeking a connection between why these different books excite me so much is when we predict how other people are going to behave and whether to punish them, we infer minds in them. I can’t see inside your brain, so I’ve got to create a mind for you based on your expressions, the things you say to me… that changes how I judge you and how I treat you. Yet, if you’re doing the same thing about me, it’s probably quite useful for me to be having a bit of my brain that’s working out what you’re inferring about me from my actions. That’s one way of explaining the evidence that Wegner pulled together, that we have this illusion of conscious will and we infer the causes of our action, not because we actually need to do this to work out why we did what we did— our brain probably doesn’t need that information and it could collect it from its own modules—but because in the way I’m building a model of your mind, reading your mind, it’s helpful for me to have some sense of what you’re thinking about me.

That observation very naturally fits in with something about the evolution of morality. I think it gives an evolutionary explanation for the otherwise odd things that Wegner has collected. Like Steven Pinker had to get rid of people’s idea that they already knew what language was about, I had to get rid of this idea that everybody knows what morality is about—that it’s about being nice to each other, nothing to do with evolution at all.

If you think that morality no longer proffers genetic advantages, does that indicate we will evolve to become less moral?

This is an intriguing thing. If you look at rich people, and more creative people, they both seem to have fewer morals. You can measure this. Who speeds through traffic lights, who doesn’t stop at traffic lights, it’s the people in the nice cars. Who takes more money? It’s the people in the higher social class. This seems to cut across the idea of morality altogether, because morality would never have evolved unless you’re more successful by being moral. So something’s gone wrong today, which means it’s inverted.

We’d only evolve to be less moral if the people who society saw as successful, the more creative people and the rich people, were also having more children. And I don’t think there is evidence of that. In fact, generally, the evidence is the other way, that poorer people tend to have more children. So in a perverse way, you’ll probably end up evolving to be more moral, because being more moral makes you poorer, and when you’re poorer, you have more kids.