Bloom’s “Just Babies” and our obsession with moralising sex

I’ve just finished reading Paul Bloom’s “Just Babies: The Origins of Good and Evil“, it is an enjoyable read that flows easily and never demands too much from the reader. Importantly, I did find in it one idea that I wish I had myself, a very welcome, and somewhat unexpected reward.

First things first: what is the book about? Despite the title, it isn’t “just” about babies, and doesn’t really delve into the deep philosophical difficulties that inevitably swallow those who dare trying to figure out where Good and Evil (with capital letters) come from. Instead, it is an erudite and quite comprehensive summary of what psychology (developmental and evolutionary) has to say about our innate moral inclinations. For me, considering what I’ve been writing so far, it is an important contribution, as it makes it very difficult to deny that we are born with a moral sense, and that the existence of this sense is entirely justifiable through the lens of evolutionary biology.

Considering the recent findings of the Pew Research Center “Global Attitudes Survey” (citation is below), this isn’t a small feat: apparently the vast majority of our fellow human beings are convinced that one needs to be religious in order to be moral. The exceptions are most of the wealthiest countries, and, unsurprisingly, China (the dependable Jerry Coyne has a good commentary, if you are interested you may want to check it out). In other words, the claim that human morality is the direct consequence of our evolutionary history is by no means uncontroversial, especially in the US, and Bloom provides a no-nonsense, balanced, and carefully worded summary of the evidence. Sometimes it seems that he deliberately tried to be accommodating and overtly concerned with avoiding bold and/or controversial claims. Given the amount of neuro-hype that circulates today, I guess it’s safe to see this as a rare quality.

What you’ll find: the book is a summary of (mainstream) developmental and evolutionary psychology research on morality. You’ll get citations from the usual suspects, such as Bloom himself, Greene, Haidt, Knobe, Pinker and many others, all peppered with some easily accessible philosophical considerations. If you are familiar with this body of work, it’s likely that the book will deliver a limited amount of new insights, it may even disappoint. If, however, you are not initiated, and more importantly, if you think that mixing science and morality is an unjustified (or even unjustifiable) effort, then this book is a Must Read. It will gently guide you through the main arguments, and if you think that morality is outside the reach of science, it may even change your mind.

In my case, I found relatively little to be excited about, but being already very interested in the subject, it is hardly Bloom’s fault. One single thing however got my unconditional attention; it is about sexuality and the strange obsession that we have: humans seem unable to consider sexual practices without using the moral lens, and this is unfortunate (as it frequently produces oppression and violence) but also surprising. Bloom points out correctly that there is no obvious evolutionary reason for this:

Our moral response to certain sexual activities is really puzzling from an evolutionary point of view. Most of the moral judgments I have been discussing throughout this book can be understood as evolved adaptations.
The mystery for moral psychologists isn’t why we would engage in certain types of sex while avoiding other types; it’s why we should be so concerned with the sex that other people are having.
For example, sexual intercourse between two people of the same sex is forbidden in much of the world and is sometimes punishable with death.[…] given the fierce nature of mate competition, it makes no sense for men to be bothered by other males who are exclusively homosexual.

He is of course, right. Our obsession with sexual morality is in part fairly straightforward: the fact that we are inclined to condemn cheating and rape have solid and pretty obvious evolutionary explanations (males don’t want to invest our resources on someone else’s offspring, females want their partner to stick around and collaborate to the difficult task of raising children; rape is violent, and our condemnation of it falls easily in the fold of conflict-reduction adaptations). But why are we so concerned about all forms of slightly unconventional, but clearly consensual sexual practices? Also: why do we usually consider prostitution immoral? (Bloom doesn’t address this second question, to be fair)
These are interesting questions, and Bloom provides a quite solid, but still hypothetical, answer. It comes in two parts:

  1. It is important to note that disgust (say, our standard reaction to sick and all sorts of biological fluids) is an obvious adaptation. It keeps us away from the most likely sources of infection, and is a very physical and largely ubiquitous mechanism.
  2. What is interesting, is that disgust is coupled to more complex higher-order reactions, that can be linked to our (other) moral instincts: we are naturally inclined to cooperate in groups, but also to see members of competing groups as alien, not worthy, and even inferior. This drives strong intra-group cohesion, and lowers the moral inhibitions towards members of other groups. Bloom notes that feelings of disgust are able to influence our moral reasoning: if we are disgusted (by some fluid/taste/odour) we are more likely to tighten up our moral judgements. He also points out that our adverse moral reactions on the sexual domain are always coloured by disgust.

The idea therefore is (presented here in my own words/elaboration): the straightforward disgust for potential sources of infection applies to all sexual activities, it is no mystery that sex is indeed a high-risk activity in terms of disease transmission. However, our sexual drives need to be able to override the normal aversion for bodily fluid exchanges, otherwise we would have gone extinct a long time ago. The side effect of this disgust+override mechanism is that when we don’t recognise (can’t empathise with) a particular sexual desire, the default mode (disgust) remains active. Since disgust has been enriched with moral overtones (hypothetically, as a reinforcing mechanism to sustain the Us vs. Them distinction, a mechanism that has clear and straightforward evolutionary origins), we find ourselves naturally inclined to morally condemn any  sexual practice that we subjectively consider undesirable.

The whole “explanation” is speculative, but backed up by solid data: the links between disgust and moral judgement, as well as between disgust and organic fluids are both well documented and supported by common sense.

Bloom concludes:

If I am correct, the moral outrage directed toward those who engage in incest, homosexuality, bestiality, and so on is not a biological adaptation. […] Instead, this aspect of moral psychology is a biological accident.

I tend to agree, and think that this discussion alone is enough to recommend reading the whole book.

The other consideration that I wish to express about this book stems not from the book contents, but specifically from what Bloom does not discuss: cooperative groups normally have leaders, and leadership generates entire families of moral/evolutionary problems. However, Bloom and (to my knowledge) most Evolutionary Psychology, largely ignore the effects that leader/subordinate relationships would have had in shaping our moral instincts. This is both regrettable and understandable, but will have to be discussed in another post (I also hope it will allow me to link power-relations, morality & disgust with our puzzling moral inclinations towards sex workers: why is it so common to consider prostitutes morally inferior?).


Bloom, P. (2013). Just Babies: The Origins of Good and Evil. Random House LLC. ISBN: 978-1847921628

Pew Research Center (2014). Worldwide, Many See Belief in God as Essential to Morality, Other:

Tagged with: ,
Posted in Ethics, Evolutionary Psychology, Psychology, Review
4 comments on “Bloom’s “Just Babies” and our obsession with moralising sex
  1. That’s making the issue of homosexuality overly complicated. First, the family is the primary social unit. That implies parents, children, and grandchildren. Normally, sexual desire and gender go hand in hand to produce offspring. Homosexuality is a handicap that interrupts the formation of families. Because most of us view the opposite sex as sexually desirable, it seems “queer” when someone is attracted instead to the same sex. And that has been the historical reaction: “something is wrong here”, “you’re not doing that right”, etc.

    Like left-handedness, it was different, misunderstood, and feared. Nothing complicated here, just a normal human reaction to something unusual, outside our understanding.

    There is probably no innate negative reaction to same-sex sex. It is more likely a learned/taught taboo due to the interference with the creation of families. Prior to the taboo, it is likely that everyone was/is bi-capable. But to prevent our children from being seduced into a non-productive relationship, we made it taboo.

    Today, we understand homosexuality as a naturally occurring anomaly in human and many other sexually reproducing species. When viewed as a handicap to normal mating, we can sympathize with those affected, and accommodate their handicap as we would any other. One of those accommodations is same-sex marriage.

  2. P.S. I watched the National Geographic program on Alexander the Great last night (why do they schedule basketball games at 10PM anyway?). Alexander’s father, king Phillip, had both male and female lovers. In ancient Greece this was apparently commonplace. The taboo is most likely a learned response and not at all instinctual.

    • Sergio Graziosi says:

      And, surprise(!), this one is easy 🙂
      I am not (and I don’t think that Bloom is) arguing that our repulsion for this or that unconventional sexual practice is innate. What Bloom provides is a possible explanation of why it happens (by accidental synergy of disgust, it’s connection with our moral “sense” And Culture), why it is so destructively strong and why it is so hard to get rid of it.
      It is a plain fact that different practices are perfectly accepted in certain cultures while they are violently condemned in others, it means that culture has a very important role in initiating and sustaining such (puzzling, from the evolutionary point of view) repulsions, I wasn’t dreaming of negating this!

  3. […] are lots of people who study moral psychology with an eye for evolutionary explanations. I’ve briefly discussed Paul Bloom‘s latest book: “Just Babies: The Origins of Good and Evil“, if you want to […]

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Follow me on Twitter

All original content published on this blog is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
Creative Commons Licence
Please feel free to re-use and adapt. I would appreciate if you'll let me know about any reuse, you may do so via twitter or the comments section. Thanks!

%d bloggers like this: