In front of the chimpanzee enclosure of Primate Research Center of Emory University Michael Tomasello and a colleague enthuse about the incredible parallels between chimpanzees and people: the emotions, the interaction, the use of tools! That's until a monkey on a climbing frame starts to pee and another sits down underneath him and opens his mouth. Okay, so they are similar but clear differences remain, the psychologist notes. That was in 1980. During a personal review of 2018 he recollects: “At that moment I could vaguely see how exciting it would be to compare apes and human children in their development.” Tomasello had found his life project: First at Emory University in Atlanta, later as director at the German Max Planck Institute for Evolutionary Anthropology and at the Wolfgang-Köhler-primate research centre in Leipzig, he devoted himself to the study of the behaviour and abilities of chimpanzees, bonobos, gorillas, orang-utans and human children. In 2016 Tomasello, who by this time had received many awards, returned to the USA and is now researching at the Duke University in Durham, where he once studied.
They are similar to us and yet not — that makes the great apes so fascinating. For Tomasello they are a tool for gaining knowledge, a mirror, that makes us more aware of the peculiarities of our own species. By comparing ourselves to the monkeys, we can better understand what makes a human tick.
If we look at people through the lens of evolution, it is above all the similarities and gradual changes which emerge. Many researchers emphasise that which is not different between man and ape. They attribute basic differences to clumsy research methods which fail to show what the monkeys are really made of. Tomasello, on the other hand, zooms right in on the differences. From this perspective, he completed numerous technical essays as well as many more accessible books, about, for example, the origin of thinking (2002 and 2014), communication (2009), cooperation (2010) and morality (2016). In his new book he summarises his earlier work, spinning a retrospective thread that connects them, giving us an answer to the big question of what separates a human from an ape. What is it that leaves us standing outside the monkey house while they sit inside?
The more similar animals and humans are, the more likely it is that scientists fall into potholes
The book wouldn't have 540 pages if the answer could be summed up in a catchphrase, but at its core, it boils down to what Tomasello calls “collective intentionality”, or people’s ability to look at the world collectively, to put our heads together and pursue projects. For Tomasello, the key to this insight lies in ontogenesis, the development of the individual (as opposed to phylogeny, the origin of the species).
Change, the author explains, does not only happen because of mutated genes, but above all because of how existing genes are read and the role they play in the development of the individual. He analyses this development in great apes and human children in terms of social cognition, that is, the ability to perceive others and take on board their perspective. He also examines communication, cultural learning and above all our “unique human sociability”, meaning our ability to cooperate with others.
Monkeys can work together, for example in hunting, they can imagine what a fellow creature sees - and then hunt for the snack that's beyond their field of vision. And if done deftly, apes can also pass the famous test for false beliefs: They can understand that another individual can believe something that doesn't correspond to reality. However, according to Tomasello, monkeys, even the great apes, are essentially egoists, both in their knowledge and their morals. They can't think beyond working to their own advantage: even when it comes to the distribution of the booty it is every monkey for themselves. Chimpanzees do not carry prey into the group and negotiate how it will be shared out. And also when they follow what another monkey can see, they do not relate his perspective to their own, but rather use this knowledge solely for their own purposes. Tomasello describes how they do not focus on “alternative perspectives.” He dubs this “individual intentionality”: The monkey views at the world as an individual and makes the best of it along those lines.
Humans, on the other hand, understand that the world looks differently to others. Already at around nine months, human children gain the ability to share their perspective, Tomasello says, making others aware off something or following someone’s gaze or gestures. By the age of three, children begin to understand how to work together toward goals, they start playing together, rather than side by side. They also learn to see their own view in the the light of other viewpoints, and become aware it is possible to have different perspectives on the world, and that there is such a thing as reality that goes beyond what we think. They also understand that they can check an opinion by asking someone. To do this, they must first decide who to ask and to who to trust. They learn to identify the position of individuals in the group and a whole world opens up to them of complex social dynamics within human relationships. This includes standards and expectations, pressure to conform and the ability to question one's own actions.
All this taken together, according to the author, made it possible to spark the beginning of a new evolutionary process: culture. In a culture, knowledge and skills are passed on to the next generation via teaching, demonstrating and correcting behaviour. This creates a sort of “jacking effect” whereby rather than starting from scratch, each generation builds on the work of its predecessors, thus reaching new heights.
Naturally also this perspective ignores evolution. “Evo-devo”, evolution and development, is the approach that combines both perspectives. Tomasello calls this approach “neo-Vygotskyism” because it recalls the thoughts of the Soviet psychologist Lev Vygotsky who saw the human psyche as developing in childhood amid exchanges with others, and “neo” because it incorporates the evolutionary perspective. In the course of evolution, there are fundamental abilities, which both humans and apes possess. But, as the child develops within human culture it does so in a typically human way. Many psychological processes, communication, learning, helping and social evaluation, existed even before humans, but only the humans’ individual development process transformed them into human psychology, something he refers to as a “maturation” process.
Human children offer toys to others, whereas apes do not, even when humans encourage them
This theoretical framework is an impressive result of decades of research, but most of it has been set out in his earlier books. What's new is Tomasello’s emphasis on the role of individual development, as well as the inclusion of results of numerous studies carried out in Leipzig in recent years. Most fascinating is how Tomasello details how his conclusions developed over time. The more similar animals and humans are, the more likely it is that scientists fall into potholes. Also the differences in the child development of humans and apes are hard to see. It's a case of honing the findings from repeatedly and meticulously modified studies. Tomasello reports of cunningly designed studies and lengthy discussions about the best interpretation of their results, new experiments, for example with the help of thermographic cameras to measure what makes an item worthy of an individuals attention. Only this detailed description (which also puts demands on a reader's patience) makes clear the complexity of this kind of research: How do you get monkeys and human children to participate? What must a task look like so that it is suitable for both and presents a comparable challenge? What can even be extrapolated from the behaviour of a captive monkey in a cage? What emphasis should be placed on “uncontrolled” reports on the behaviour of free living monkeys in comparison with studies involving zoo animals?
Tomasello discusses numerous points of criticism levelled at his research which focused on the differences and he repeatedly mentions the lack of extensive studies and the problems of conducting research into young monkeys. Linguistically he remains cautious and deliberate, but his points are ultimately confirmed over and over again: Yes, monkeys have a certain idea of simple physical relationships, they understand where the other person is looking and sometimes they help each other. But human children develop social skills much earlier: what they can do at the age of two cannot be seen in chimpanzees until they are four years old. Human children smile at their caregivers but apes do not exhibit such emotional interaction. Human children offer toys to others, whereas apes do not, even when humans encourage them.
Bit by bit, and repeatedly with illustrated diagrams of development processes, Tomasello puts together the image of a “hypersocial” species, whose individuals are increasingly closely connected: even in early childhood, humans correct their own behaviour in keeping with the expectations of the group. This is how a community is created, which can plan and cooperate and is therefore much more flexible than the primate kinship which always prioritises personal advantage.
The many details, studies and assessments which Tomasello uses to support his theses mean that the book is far from an easy read. The author writes about science so it can be understood but without sweeping narratives. But, along the way, readers obtain an impressive overview of comparative primate research and an understanding of how closely you need to zoom in to establish what makes us humans and what makes monkeys into monkeys - and also how many questions are still wide open.
Becoming Human: A Theory of Ontogeny. By Michael Tomasello. Harvard University Press.