Cognitive Science: An Introduction/Evolutionary Psychology

Evolutionary psychology is an approach to doing psychological science that uses considerations of selective pressures to hypothesize about the nature of current minds, in both animals and humans. A key part of evolutionary processes is that when we look at a characteristic of something now, and theorize about how it got there, we need to keep in mind that every intermediate state wasn't maladaptive.

Evolutionary psychology got started in the late 1980s, kicked off with the publication of The Adapted Mind: Evolutionary Psychology and the Generation of Culture,[1] in 1992.[2]

What does this mean? Well, if you are creating a consumer product, you can completely destroy it and try something completely different. You can build and design for a long time, during which your product might not work at all. Evolution can't work this way. Evolution's design problem, you might say, is like trying to design a better and better house while people are still living in it the whole time.

Evolutionary psychology is typically concerned with traits that are generally present in a particular species, rather than trying to explaining variation of traits between individuals in a species.

What kinds of cognitive tasks might have been evolved?Edit

It's very important to understand that nearly every trait a human being has was influenced by what they've experienced in the environment, often affected in some way by their genes. But almost nothing is 100% genetically determined. The exceptions are Huntington's disease, eye colour, blood type, and maybe a few more.[2] Just about everything else is a complex combination of genetic and environmental influences. So when we talk about genes for this or that, always keep in mind that we're talking about a genetic influence on a complex process that interacts with the environment.

In regards to animal behavior, including human behavior, we can broadly classify them as 1) adapted, meaning it evolved due to natural or sexual selection, 2) a byproduct of another adaptation, 3) it is culturally learned, or 4) it is figured out by each individual by individual learning.

When we are trying to understand how minds work, some of the things we are able to do were not, in any important sense, evolved, such as demonstrating knowledge of the rules to Dance Dance Revolution. There's no gene for spears being thrown pointy-end first, even though it's cross-cultural. So what kinds of cognitive tasks should we even be looking for evolutionary explanations of? Here are some characteristics. We might think of these characteristics of things that are "innate." For us to think something is innate might not require all of these characteristics, but the more we have, the better the evidence is.

Present in the UnenculturatedEdit

Characteristics present at birth, that is, before culture has had time to affect the organism, are more likely to be innate. Humans learn some things in the womb, but very little.

Some innate things, such as the onset of puberty, are obviously not present at birth. They are set to respond to certain environmental conditions. This means that it's not necessary for a characteristic to be present at birth.

Similarly, if it is present in hunter-gatherer cultures, who have not been exposed to modern society, it supports the notion.

Cross-Species and Cross-Cultural ObservationEdit

The ability to walk, or, at least, the ability to learn to walk, is seen in many species, including dogs and caterpillars. It's seen in every human culture ever observed. That makes it more likely to have been an evolved trait.

For example, all cultures have languages. Of course, individuals have to learn a particular language in a culture, but we do this effortlessly. That is, we don't even have to teach people how to speak. They learn it themselves. So many cognitive scientists think we have evolved the ability to learn language. In contrast, take reading and writing. This takes intense training--so much that illiteracy is a problem in many places. The fact that it takes difficult, sustained intervention to get people to learn to read and write puts it in a different class of things from learning to speak. Also, writing was only invented only around 3000 BCE, and has only been independently invented on Earth a few times. We didn't evolve to read and write.

We must take care, however. If we look across cultures, we can see that spears are thrown pointed-end first. But it would be foolish to suggest a genetic predisposition for this.[3] We have intelligence, and every person can figure out, without the help of a specific genetic tendency, that spears work better that way.

The Characteristic is HeritableEdit

If individuals who have the characteristic give birth to offspring who share that characteristic, this is support that the characteristic is innate. Of course, in humans, often offspring also share the culture of the parents, introducing a confound. This is why separated twin studies are so important.

Evidence of Genetic PathwayEdit

It helps if we can find specific genetic codes that seem to cause the characteristic.

Selective Pressures from Long AgoEdit

There was no internet for most of the history of human evolution, so any theorizing about the selective pressures that the internet has put on us cannot explain large-scale cognitive abilities we see in people throughout history. For a trait to be evolved, it needs to have been selected for over a very, very long time. In general, if we can't think of how there might have been selective pressure during our long evolution in the pleistocene, we don't consider it a good task for evolutionary psychology. That is, high adaptive value for long periods of natural selection.

Walking, again, is a great example. Creatures who locomote (change their location through their own activity), and don't do it a completely stereotyped way, need some way to, at the very least, detect things they want to approach (such as food or mates) and things they want to avoid (such as dangers). We see this in very simple organisms as well as all mammals, including humans. It's probably an evolved trait. Incidentally, it's also likely to show similar patterns (across individuals in the species) in development. This is called canalization--where all individuals in a species (without some relevant disorders) will go through the same stages.[4]

The Gene's-Eye ViewEdit

It's natural to think of evolution happening to individuals. That is, a particular person, or raccoon, or bacterium survives and reproduces. But another useful way of looking at it is from the point of view of a gene. That is, it's the gene that gets better represented in the next generation. This idea was introduced by Hamilton,[5] and popularized by Richard Dawkins in his book The Selfish Gene.[6]

It helps explain some aspects of human and animal behavior. For example, why would a salmon kill itself trying to get to the spawning ground? The salmon who don't end up not reproducing. But we can see that the salmon is not acting in the best interests of itself, but in the best interests of its offspring. More specifically, its offspring's genes.

More broadly, we can see this at work in what's called kin selection, which is the tendency of individuals to help out their relatives more than strangers. Indeed, studies have shown that people are more likely to help, and less like to use violence against, their relatives.[7]

But more broadly, even if two individuals are not related, they will tend to help each other more if they share genes. This is Hamilton's inclusive fitness theory: an individual's genetic reproductive success is the sum of the reproduction of individuals carrying the same genes.[5] In support of this, people tend to marry others with similar genes, as expressed in perceivable characteristics, such as whether or not the earlobe is connected to the head, distance between the eyes, and even lung volume! People who look more alike tend to stay married.[8]

Basically, this means that animals, humans included, evolved to try to propagate their genes, not just reproduce themselves--though that is often the most efficient way to do that.

Mating StrategiesEdit

Reproduction is necessary for evolution, and as such all sexually-reproducing species have evolved ways to try to increase their genetic representation in future generations by having mating strategies.

Many mating strategies discovered by evolutionary psychology stem from the biological differences between males and females. In short, females pay a much greater cost to reproduce, as they have to carry and deliver the offspring. As such, females tend to be pickier about their choice of mates and tend to be more interested in mates who not only have good genes for survival, but who also show promise to have the ability and desire to help raise the offspring.


The differences in biology also predict the kinds of jealousy that men and women tend to feel. Women are more in danger of being left to raise children alone, and men are in danger of raising children that are not theirs, biologically. As such, men tend to be more jealous of sexual relationships, and women tend to be more jealous of intimate, emotional relationships.

It seems that men have good reason be sexually jealous, evolutionarily speaking, because women seem to have a differential mating strategy. When looking for biological fathers, they tend to go for more rugged men with good genes for survival, and when looking for a partner in life, they tend to look for more nurturing men. The result of this is that, cross-culturally, about 10% of babies born have a different biological father than the man who has his name on the birth certificate.[2]

Eating and HungerEdit

Like mating, eating is another essential factor in the success of a species. Although many contemporary humans are not starving, hunger and starvation has been a danger for most of human history [9] (and, indeed, animal history), so our psychology is in part shaped by the need for food.

  1. Barkow, J. H., Cosmides, L., & Tooby, J. (Eds.). (1992). The adapted mind: Evolutionary psychology and the generation of culture. Oxford University Press, USA.
  2. a b c Miller, A. S., & Kanazawa, S. (2007). Why Beautiful People Have More Daughters: From Dating, Shopping, and Praying to Going to War and Becoming a Billionaire: Two Evolutionary Psychologists Explain why We Do what We Do. New York: Penguin.
  3. Dennett, D. C. (2017). From bacteria to Bach and back: The evolution of minds. New York: WW Norton & Company.
  4. Newcombe, N.S. & Learmonth, A.E. (2005). Development of spatial competence. In P. Shah and A. Miyake (Eds.) The Cambridge Handbook of Visuospatial Thinking. Cambridge University Press: Cambridge. 213--256.
  5. a b Hamilton, W. D. (1964). The genetical evolution of social behaviour. II. Journal of theoretical biology, 7(1), 17-52.
  6. Dawkins, R. (1976). The Selfish Gene Oxford University Press. New York.
  7. Burnstein, E., Crandall, C., & Kitayama, S. (1994). Some neo-Darwinian decision rules for altruism: Weighing cues for inclusive fitness as a function of the biological importance of the decision. Journal of Personality and Social Psychology, 67(5), 773.
  8. Diamond, J. (1992). The Third Chimpanzee: The Evolution and Future of the Human Animal. New York, New York: Harper Perennial. Pages 101—103.
  9. Pinker, S. (2018). Enlightenment Now: The Case for Reason, Science, Humanism, and Progress. Viking: New York. Page 25.