Becoming Human TomaselloI’m always eager for the year-end list of David Auerbach at Waggish. The man is a voracious reader in all kinds of domains. 2019’s list was dauntingly long, but I found a few titles right up my ally, one being Becoming Human: A Theory of Ontogeny by Michael Tomasello, Professor of Psychology and Neuroscience at Duke. Tomasello is one of the few scientists bridging developmental research on both primates and children, and a leading figure in a branch of evolutionary psychology that was new to me: human ontogeny.

The book focuses on the question what makes humans unique. It does this by focusing on how children become adult humans, and as such part of human culture – how the development of human abilities in children differ from the development of these abilities in great apes.

Tomasello’s scope is large. He ties the development of human cognition and human sociality together, resulting in synthesizing insights about social norms & moral identity. This in not only a comparative psychology book, but an important work on ethics too. Truly a tour de force, and the first theory I’ve come across that convincingly brings cognition, evolution and ethics together – not in a normative way, but by describing the pathways of how these things arise, starting with newborn babies.

Tomasello builds on the seminal insight of Lev Vygotsky, who in the beginning of the 20th century was one of the first to articulate the fact that children need a social context to develop fully. A child that would be put onto a desert island without any social interaction would not become ‘human’ as we generally define it.

To further sketch the content, let me first quote the blurb from the publisher – Harvard.

Tomasello assembles nearly three decades of experimental work with chimpanzees, bonobos, and human children to propose a new framework for psychological growth between birth and seven years of age. He identifies eight pathways that starkly differentiate humans from their closest primate relatives: social cognition, communication, cultural learning, cooperative thinking, collaboration, prosociality, social norms, and moral identity. In each of these, great apes possess rudimentary abilities. But then, Tomasello argues, the maturation of humans’ evolved capacities for shared intentionality transform these abilities—through the new forms of sociocultural interaction they enable—into uniquely human cognition and sociality. The first step occurs around nine months, with the emergence of joint intentionality, exercised mostly with caregiving adults. The second step occurs around three years, with the emergence of collective intentionality involving both authoritative adults, who convey cultural knowledge, and coequal peers, who elicit collaboration and communication. Finally, by age six or seven, children become responsible for self-regulating their beliefs and actions so that they comport with cultural norms.

At first, I was a bit suspicious of Tomasello’s claims: I have read quite a lot of Frans de Waal and the likes, and my intellectual stance the last decade or so had been to not overestimate human uniqueness – not in language skills, not in cognition, etc. I considered differences between humans and other animals basically a matter of degree.

To a certain extent this obviously still holds, but one of the merits of Tomasello is that he uses large sets of experimental data that clearly show there are two things that are unique in humans: “shared intentionality” and “collective intentionality”. Basically, the fact that we humans do things together, know that we do things together and have elaborate insights in other humans’ mental states that influence our own mental states. So it’s not only cooperation itself that is important, but the fact that it is a form of recursive cooperation.

Language obviously is important for all of this, and so this is not only an ethics book, but one that should interest linguists too. The same goes for the cultural transmission of knowledge: instructed learning basically doesn’t exist in the rest of the animal kingdom, so yes, pedagogy too.

Rather than try to summarize Tomasello’s theory, in the remainder of this review I’ll do two things: first I’ll list an extensive amount of the information I found particularly interesting – take a look I’d say, it’s the juice of this review – and I end with a short bit on the book as a book: a few words on my reading experience, not the theory itself, so that interested readers better know what to expect.

Before I get to that, I need to make one more thing loud and clear about Tomasello’s theory itself. The praise on the back of the book is very, very high. Other professors call this a “landmark in our understanding of human development”, a “scientific masterpiece”, “destined to become a classic”, “theoretically daring” and “astonishingly generative”. From my own limited perspective I’d say this praise is justified, and I learned a lot. I have a background in linguistics, and I have to say the chapter on communication is fantastic. I’d even say reading this book shifted my paradigms a bit – or at the very least refocused them on recursive cooperation as the quintessential aspect of human nature. Humans are not individuals – John Donne was right when he wrote ‘No Man is an Island’.

As for a thorough summary, best to watch Tomasello himself: there’s a one hour talk on YouTube, and he shows loads of videos from experiments too. It’s basically a synopsis of the book.


The list bellow isn’t exhaustive, nor is it an attempt at a summary. It’s just things I want to remember from this book myself. I quote disproportionately from the language parts of the book, but there’s other great stuff too, on guilt, ethics, autism, hunter-gatherers, the birth of reason and something very surprising about Frans de Waal’s famous capuchin monkeys.

  • “Modern evolutionary theory emphasizes that organisms inherit their environments as much as they inheret their genes: a fish inherits not only fins but also water. Human children inheret a sociocultural context replete with cultural artifacts, symbos, and institutions, and their unique maturational capacities would be inert without a sociocultural context within which to develop.”
  • Primates are clever, but mainly/only as individuals.
  • “Language additionally contributes to the sense of an objective perspective on things, as it enables one to express generic propositions about the world in general.”
  • Great apes and other animal species don’t distinguish between objective and subjective thinking. Some species are “able to imagine what another individual is experiencing or has experienced, but they do not contrast this with what they or anyone else is experiencing or has experienced either, much less with an objective perspective.”
  • In all 4 nonhuman ape species, childcare is basically 100% by the mother, whereas in humans, after early infancy, it is only about 50% of the care, the other half provided by fathers, grandmothers and friends. This is cooperative breeding presents unique cognitive and social challenges for the infants.
  • “Around 3 years old, children come to understand the cultural common ground they share with all others in their cultural group, (…).”
  • Chimpanzees compete rather than cooperate. Even when they hunt in group for smaller monkeys, it is not really cooperation as humans define it, but each ape in pursuit on its own.
  • “Linguistic communication is an extension of natural gestures. Both are invitations to jointly attend an external situation for one of several cooperative motives.”
  • There are chimpanzees like Kanzi that have been taught symbolic labels (words), but human word “learning is (…) not about putting labels on things but rather is about acquiring conventional means for coming to share attention with others in a variety of complex social contexts.” Moreover, there is a normative dimension to using words, and thus the understanding of ‘conventionality’ is an important prerequisite for human language.
  • Human languages invite to conform to their conventions and at the same time empower “the individual to go beyond them.”
  • 95% of what apes like Kanzi communicate are imperatives. The other 5% are the result of naming games. That is not even close to real human language. They also do not use pronouns. They are “almost totally lacking” “skills of intention-reading”, necessary for “using appropriately different words and constructions adapted for different recipient’s knowledge, expectations and perspectives.”
  • “Monitoring what others comprehend of one’s linguistic expression of one’s thoughts is a fundamental process in learning to think and communicate rationally – that is, in conformity with the culture’s norms of rationality.”
  • Autists generally have a problem with joint intentionally & joint perspective. 50% of autists do not acquire language.
  • Tomasello makes a pretty strong claim vs. Chomsky. I’ve recently read David Adger’s Language Unlimited and he made a pretty solid case in favor of Chomsky. Maybe Tomasello’s claim is more valid, as he is an experimental psychologist, and that might ultimately be better a approach to the question than from a purely linguistic angle. I’m on the fence at the moment, thinking there might be truth in both claims – also Tomasello at the end of this book acknowledges the complex interplay between nature/nurture, maturation/experience, genes/environment, innate/learned – these are not mutually exclusive alternatives.
  • For children to become adults, peer talk & play is very, very important, as they need to practice & develop without the limits inherent in the asymmetrical relation between child & adult. In an equal status dialogue, reason can prevail, not power. So such interactions are crucial to develop a normative and reasonable self-governance. (I’d say: it takes a village, including other children, to raise a child.)
  • Human pedagogy borders on the incredible, if you think about it. Children in modern societies learn about “a plethora of things with which they have no direct experience” (Pluto, dinosaurs) or “could never invented on their own” (literacy, numeracy).
  • “Mercier and Sperber (2011) proposed a novel theory of human reason-giving, grounded in human evolution. Their proposal is that as human societies grew larger, problems of trust became more prevalent. In a group where everyone knows everyone, and everyone encounters everyone on a regular basis, trust is maintained because an untrustworthy person would be identified and excluded quickly. But in larger groups this is difficult, so individuals had to start practicing “epistemic vigilance” – that is, being careful about what to believe. In this kind of social context, one could not expect others to accept a perspective or argument on trust. Individuals therefore started giving other reasons for why they should believe what they were telling them (….).’
  • So, in conclusion, being reasonable is fundamentally cooperative. We don’t reason very well on our own.
  • The evidence for humans being moral beings is very strong: 3-year-old children are observed acting morally in numerous settings, and they don’t act that way purely instrumental – because of possible reputational damage if they don’t, nor out of strategic considerations.
  • There’s very strong evidence toddlers have the intrinsic (biological) urge to help, and not because of possible rewards. (I would like to add to this the remark that as such, the idea that all altruism is basically disguised egoism as one expects a reciprocal act is not valid – that is, it is not part of conscious reasoning – but of course a similar chain of reasoning in our less morally developed ancestors might still be at the base of the natural selection that installed our biological urge.)
  • There’s the famous experiment with the capuchin monkeys that supposedly proves they have concepts of fairness. Tomasello points at other experiments with different controls, that discredit such an interpretation: these monkeys are not angry because of (social) inequity, but because of their expectations not being met.
  • Apes don’t retaliate against those who harm third parties (unless they are in a coalition). As such, they don’t have a concept of ‘justice’.
  • According to Marlowe, “some contemporary hunter-gatherers rarely engage in norm enforcement or third-party punishment; they mostly just move away from norm violators. But the fact is they do punish violators when leaving is not an option, and they punish violators reputationally through gossip on a regular basis.” I think this is interesting as hunter-gatherers are also known not to have social stratification based on possession. As such, they provide an interesting peek into a transitional phase in societal evolution.
  • Because “individuals played the role of both judger and judged – with ‘our’ shared standards in the group applying in both cases – they came to evaluate themselves in the same way that they evaluated others, thus creating an internalized moral identity.” This is a great evolutionary explanation of the Golden Rule – do unto others as you would have them do unto you a maxim possibly 4 millennia old, but then in reverse: judge yourself as others would judge you.
  • The feeling of guilt stems from the fact that ignoring the moral judgements of the group de facto means that one renounces one’s identification with his or her group, while the group is crucial for one’s sense of identity. As such, guilt is clearly a conflict within oneself.
  • Adam Smith already claimed in 1759 we do not act prosocially to be praised but rather to be a praiseworthy person. That is, to be praiseworthy in the eyes of the community, and that includes ourselves, as we are part of the community.

A few final words on the book as a reading experience.

Becoming Human has 379 pages, including about 30 pages of references and a 7-page index. The prose is clear and steady. Every chapter or subchapter starts with a broad outline of the particular topic, then focuses on what we know of the matter from great apes, moves to an overview of all the relevant experiments with human children, and ends with a summary. If they are available, Tomasello also explores the data for possible intercultural variation and children with autism. There are introductions to sections that basically repeat stuff too, and at the very end there are about 40 pages that are mostly a summary of the entire book. So, as a pure reading experience it’s not fully successful: there is too much repetition. But, this is not a popular science book, and as such should not be judged that way.

All the repetition allows for other scholars to just read a particular chapter of the book depending their needs, and also the broad introduction that’s a summary of some sorts, as is the summary at the back, are great for professionals to determine what parts of the book they might want to read in more detail.

Likewise, for the casual reader – like myself – the never-ending flood of experiment after experiment can become a bit tiresome at times. Not that this stops being interesting – all the experiments are interesting in and of themselves – yet there are so, so many of them. Again, from a scientific point of view, this is only a plus. Tomasello cements his theory more than firmly: it’s rock, rock solid. He also refutes some criticism, taking a middle ground between ape “scoffers” like Povinelli, Vonk, Lurz and Heyes, and ape “boosters” like de Waal and Boesch. He does so convincingly, if you ask me.

Obviously, this theory is not fully complete, and the book ends with prospects for further research.

So: casual readers beware / this is highly recommended.


Here is a link to my other non-fiction reviews, and a link to a list of my favorite non-fiction books.

16 responses to “BECOMING HUMAN: A THEORY OF ONTOGENY – Michael Tomasello (2019)

  1. This sounds fascinating and right up my alley! I was always partial to social linguistics, and primatology, so this sounds like a book tailored for me!
    Great review, Bart!

    Liked by 1 person

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  5. Going for short vacation, I packed my Kindle this time, and decided to finally read this – not a typical beach reading, but I find it easier to concentrate on such stuff when I’m removed, physically and mentally, from things like work…

    Anyway, I’m impressed and fascinated by Tomasello. It was another building block added to my view on how is humanity possible, and what is unique about us.

    I find it quite accessible for a layman – frequent repetitions definitely helped 😉

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