Why does pornography exist? No seriously, setting aside the self-righteously-moral-majority. The question of red dudes with pointy horns is good for art, but isn’t particularly interesting if we want to answer real questions. Why does pornography exist from an evolutionary standpoint? Without diving into minutia, there’s not much of a survival benefit to pornography. And no, masturbating as if your life depended on it doesn’t count. Which brings up an important point. Why does masturbation exist?

Despite what Christine O’Donnell might tell you, masturbation exists in other species. Bonobos get all kinds of freaky with it. What’s interesting is that the large brained apes we are have somehow figured out a way to involve psychology in sex and mating. In a sense, human orgasm is somewhat decoupled from the mechanics. If you haven’t figured out the element of imagination or fantasy that’s involved in sex, you’re doing it wrong. But as far as we know, we’re the only species that uses pornography. There’s an interesting scientific article from 2005 that’s often cited as evidence of “monkey porn”. The article does have some fascinating implications, however, it’s not about porn. The reason it’s often mistaken for monkeys indulging in pornography is that male monkeys were willing to pay (using fruit juice as a currency) to look at pictures of females. But the monkeys didn’t mix this viewing with masturbation. It appears that they were examining the photos for visual signs of fertility. That’s important information for evolution, information worth paying for.

It’s also likely that humans are using the same visual cues to make determinations about potential mates in human pornography. However, we don’t think about that when we experience porn. Humans have decoupled the cues for fertility with the concept of fertility. And in humans this makes a lot of sense because unlike the rhesus macaques mentioned in the study, human ovulation is biologically concealed. So humans use the cues for visuals to fecundity (general ability to reproduce). I’ll tackle the evolved concept of beauty and attraction in another article. What’s important to know here is that humans have a very real emotional and visceral response when beauty and attraction are witnessed. And I’ll go on a limb and assume that you get that. But still, that doesn’t answer the question of the existence of pornography. And when are we ever going to get to the part where racism is proved to be arbitrary, in the grand scheme of humanity?

Biased by Nature

The answer to both ultimately lies in the second syllable of “pornography”. Yep… the graph, or visual, part. There’s a concept within sexual selection known as “sensory bias”. Basically, we use the senses we have to make the best determination of things that will increase our chances of survival and reproduction. And to be more correct, we evolved the senses we have to give us the ability to make determinations to help with survival and reproductive success. Vision is great for judging spatial distances advantageous in hunting. It’s beneficial for a zillion other things too. Color vision is great if you’re gathering fruit and need to quickly be able to discern ripeness… especially from a few trees away. For an extreme example, we even have the colloquial phrase “eagle eye” to highlight the visual prowess of birds who conduct hunting surveillance from extreme altitudes.

But all animals don’t have the same biases. In other environments, smell or sonar or sensitivity to the infrared spectrum are more advantageous. Among our many senses, humans have a decidedly visual bias. No, this isn’t fixed. Many studies show that there is an actual heightening (or hightening of awareness) of auditory sensitivity in blind people. But in general, our sensory bias is visual. It’s because of a combination of this sensory bias, big brains, and emotional complexity that porn exists. Without any of them, porn wouldn’t work on us. And yes, hearing porn has similar impacts, but that doesn’t lead us any closer to highlighting the inanity of racism.


Racism is made possible in humans by our visual sensory bias. Skin pigmentation, and other shapes and colorations are generally irrelevant distinctions in matters not relating to vitamin D and skin cancer. While our modern civilizations pile a variety of deleterious effects because of our skin pigmentation, the differences don’t play a major role in survival or reproduction (caveat: during normal reproductive years). In other words, skin pigmentation is highlighted by the human visual bias. This is similar to the underlying reason firetrucks are painted red (or yellow).

The human sensory bias combines with another group of related human biases to really drive racism into high-gear. Our bias toward grouping, ethnocentricity, and xenophobia cause us to make extreme distinctions by grouping people based on any markers at our disposal. Humans have been shown to form emotional group ties on something as little as a coin flip. This tendency to form groups was a useful decision making heuristic for our distant ancestors. In some instances, it remains so today. However, it fires way too often in individuals living in the relative safety of modern civilization. Seth Godin has tried to make tribalism sound like a good thing in his book Tribes, but that’s ultimately just a conscious attempt to capitalize on an antiquated artifact of evolution that’s largely lost its use in our world.

Racism and pornography both spring wholly from a combination of non-logical biases we all share as humans. We can debate the merits of pornography in terms of human happiness and flourishing, but racism is arbitrary and thus, completely untenable.

  1. Tom H 14 years ago

    I think perhaps we are looking for too deep a meaning with porn/masturbation. It boils down to simply a dopamine fix…the euphoric rush of the 'O'…stimulation of the brain's pleasure center..nothing more. Porn just helps us get there faster by providing the virtual setting we imagine our selves in to get to the end result.. dopamine. An accidental discovery in mice about the pleasure center of the brain (septal) resulted in the mice passing up food and water to have the pleasure center stimulated. http://www.damninteresting.com/technology-and-the

    Racism may also be rather simplistic, rooted perhaps in a primal segregation for climatic survival purposes. Skin pigment, muscle/fat ratio and density, even eyelid shape and body hair all are due to environmental factors our ancestors evolved in order to survive their particular climates. Thus racism could be a deep primal bias that someone of a different race couldn't survive (be successful provider/produce viable offspring) in ones 'home' region. This of course doesn't matter in present time since climate can be controlled (indoors), clothing evolution and new tools can make anyone successful in most climate regions. But is it reasonable to expect that primal bias to vanish? Should we be able to 'mentally evolve' past that? I would like to think so, but reality proves different.

    • Andrew 14 years ago

      I don't understand the concept of "too deep". 🙂 I want to hit the bedrock foundation and the very very bottom.

      We're not in disagreement on the proximate mechanism of dopamine reactivity. My question to you would be, why would the human mind be wired up to trigger a dopamine release at the sight of any 2D image?

      This relates to your point about regional race biases being a shortcut to identifying potential threats (a point with which I also agree)… Error Management Theory: A New Perspective on Biases

      • Tom H 14 years ago

        "…why would the human mind be wired up to trigger a dopamine release at the sight of any 2D image?"

        My guess would be that due to human brain evolution from reptilian brain (archicortex?) to mammalian (paleocortex) to human (neocortex) brain…. the visual cortex enlarged through evolution (includes Primary (V1) plus extrastriate regions through the dorsal and ventral pathways). Basically the visual information is passed on to most parts of the brain for information dissemination. We evolved to become a visual species. It makes sense that visual stimulation is more powerful…at least to my simple brain. Of course it is interesting that we pursue a complex type of stimulation to activate a rather primitive part of the brain. Our other sensory areas have declined in size such as olfactory which is in the more primitive section at the base.

        • Andrew 14 years ago

          Again, we don't disagree. The only difference is that you're talking about the how of evolution and I'm thinking about the why. That is, why did the brain get "wired up" in such a way that porn works. My thinking was that it's an odd abstraction of visual bias and cognition/imagination.

          To make that connection, it's necessary to describe the connection between our visual sense and the fitness indicators we've developed because of it that are used in sexual selection. I'll cover that in upcoming post(s) I alluded to involving beauty and attraction.

          • Tom H 14 years ago

            Ah the 'why'. I would lean more towards modern (last 2-3000 yrs) social/religious constraints but I could be way off. I would think someone has done a study (or maybe not) on 'primitive' tribes, the few that remain, and their reaction or non reaction to porn. If the society is open about sex, nudity, etc.. is porn that influential?

            I'll have to wait for your next article on the subject. Thanks for all the great info here btw…you helped start me on the paleo diet…so far so good.

  2. Christopher 14 years ago

    Have you read the book "NurtureShock"? It's about the science behind some child rearing best practices. I don't have it on hand, but it references several studies done on children that show how they are racist by default and it takes a lot of active parental involvement (deliberate discussions of, and regular reminders) to help them become aware of and overcome such biases at an early age.

    • Andrew 14 years ago

      Interesting. This is the first I've heard about it, but it looks to be right up my alley (aside from the fact that I don't have kids). It gets super-high Amazon ratings from a lot of people. Anyway, I've linked it up in your comment. Thanks!

  3. Lach 13 years ago

    Andrew, are you expecting that you can explain the wonderful complexity of the human condition in purely biological, evolutionary terms? Personally I think that's a fool's errand. Racism is just one variation of bigotry. I doubt it has anything to do with a visual bias. There's plenty of examples of people developing bigoted attitudes without having ever seen / met the subjects of their bigotry. The answer has far more to do with conditioning and fear of scarcity than biology. I appreciate your thoughtful approach!

    • Andrew 13 years ago

      Apologies, I'm still stuck typing with one hand so my response won't be as robust as I might like.

      The fool's errand you mention is commonly referred to (often pejoratively) as "biological determinism". We are in agreement on the emptiness of that line of inquiry.

      What's interesting to me is that various cultural and environmental inputs are not absorbed equally by human brains. You mentioned bigotry, I mentioned in-group/out-group bias; these are fundamentally similar (as are ethnocentricity and xenophobia). It turns out that humans are more susceptible to absorbing, developing, and maintaining this sort of bias than say… a bias toward the typeface Helvetica. Evolutionarily speaking, this served as a heuristic that conferred a survival advantage. It's safer to avoid strangers in an unknown world (especially a pre-language world). This type of behavioral shortcut is described by "error management theory", which I'll write more about later.

      Why I find this important to explore and understand is that, in the modern world, one's views on Helvetica might be more important from a rational standpoint.

      It also turns out that fear works in a non-rational way in the human brain. We generally develop fears of snakes and spiders easily, but rarely develop fears of driving 80mph on the freeway. The latter is much more likely to kill us today, but spiders and snakes provided selection pressure over evolutionary time. People with a fear of spiders and snakes tended to survive longer. Hence the cliche "a healthy fear".

      Because humans have a bigotry bias and a strong visual bias, we could predict (retrodiction may be more accurate) that a bigotry bias delimited by visual cues would be particularly likely in our species. Understanding the alignment of multiple non-rational biases is an important bit of information if we hope to survive as a species. I'd go further and say that rather than culture creating, then imparting, these biases, it has subsumed the inherent human impulses and reflects them back on us in a way that amplifies them.

      Question #3 in my (unfinished) evolutionary psychology FAQ was an early attempt to answer this type of question more generally.

      You might also glance at Blank Slate, SSSM, and Biological Determinism on my evolutionary psychology definitions page.

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