This book is about the core of human experience, what gives us both our greatest pleasures and our greatest pains, the agonies and the ecstasies: our social interactions with each other, our exchanges of words, glances, laughter, and sighs in face-to-face encounters.

I wrote the first draft of this book in the pandemic years 2020–2022. In the first wave, we buried my father, after being unable to see him in his final days and unable to hug each other by way of solace. My academic work was reduced to Zoom doctoral exams or distanced lectures. When taking a run with the dog and passing a couple talking, I was filled with envy for just simple conversation. All around us, people were feeling the withdrawal from normal social interaction as more than just a loss – it was something nearer to being marooned in space and time, as if we were all Robinson Crusoes, cut off from the world of life.

Perhaps that was the perfect moment to start writing this book, which celebrates the role of social interaction in human life, indeed in the evolution of the species. Then at least we could feel, by virtue of its attenuation, its critical importance in our normal life. It is in social interaction that we express our loves and gain the greatest rewards of our lives, and particularly the regard of others. It is also the arena of our greatest despairs, shames, and rivalries.

While the pandemic has brought out what a critical role interaction plays in our lives, the academic study of human social interaction has hardly begun. Most of what we know about it has been provided by mavericks and outliers of the main intellectual disciplines: by conversation analysts, students of kinesics (bodily signals) and gesture, researchers in non-verbal interaction, and by individuals like Erving Goffman, Harvey Sacks, Adam Kendon, Emanuel Schegloff, Gail Jefferson, Ray Birdwhistell – not household names except perhaps for the first. There is no major discipline that makes the study of human interaction a central theme, although strands of work in anthropology, sociology, and psychology do address it. In some ways we know more about the social interaction of birds and monkeys than we do about humans! The relative neglect of the study of human interaction might just be an accident, but it may also reflect the fact that we do not like to peer into the inner workings of the undercurrents that buoy us up, make us like some people and detest others, excite us or depress us.

This book tries to place human social interaction central in the human story. I believe it is the key to understanding how we came to be an articulate species, how we have been able to accumulate cultural and technological skills, and so how we have come to dominate the planet. In place of the standard view that it was language that enabled our social and cultural skills, this book argues that it was our increasing capacity for social interaction that prepared the ground for language and the attendant accumulation of cultural properties.

The story I will tell is that the roots of our communication system have a couple of unlikely sources. One was an exploitation of our pre-existing spatial cognition: in an early gestural phase of communication our messages were mostly about spatial locations in a spatial medium, namely gesture. To this day, when we talk about place, we cannot avoid gesturing. The second exploitation was another such ‘exaptation’ or re-use of existing capacities, this time a generalization of maternal caring instincts. If you have ever seen a blackbird feeding its nestlings, you will have marvelled at the way it provisions and cares for them. Compare now walking into a kindergarten and observing the selfless attention of the teachers and caregivers to their charges, trying to understand the children’s upsets, their needs, and their wants. But unlike the blackbird, the human carers have no genetic relation to the children at all – they operate as if they were their parents. A girl looks lost and upset in the street – we read her state of mind, offer directions, and see her on her way. Empathy and the ability to ‘read minds’ is essential to how language works. I argue that these two ingredients – spatial cognition and a generalization of empathy – were crucial to the evolution of language and were being tapped as the basis of an advanced communication system well over a million years ago.

In retracing this evolutionary path, it becomes pretty clear that there was a critical foundation to these developments which was our advanced capacity to understand one another, foresee each other’s actions, and so cooperate efficiently in sustained interaction. To repeat: it is interaction that made language possible, not language that made interaction possible. This special interactional ability is the subject of this book.

Setting aside the 2020–2022 pandemic and what it has done to our interactions, this book may seem at first sight quite remote from the main issues of the day, but this is far from the truth. The rise of social media has amplified some of the features of communicative interaction which governed us before farming built large human communities: the role of rhetoric and demagoguery in our politics, and the power of gossip or ‘trolling’ to take down those we envy. In the final chapter of this book I try to show how these features are built into our interactive system, and how they dictate many aspects of the shape of our social systems. Twitter (X) and other shortform social media, for example, are so successful because their brief format mimics the turns in conversation.

I have tried to write the book in a way that makes it accessible to the general enquiring public. But in a work this broad, advancing new and sometimes no doubt heretical views, I have thought it essential to keep the full scholarly apparatus of footnotes and references, indicating where the facts that have guided the argument come from. This is a ‘big ideas’ book, but the ideas are thoroughly grounded. I think it should be of interest to all who wonder about how our species came to dominate the planet but seem incapable of looking after it. In addition, it should, I hope, interest academics from a wide range of disciplines connected with human communication and social life, from linguistics to anthropology to the health sciences.

This book ranges over much of the terrain in which I have conducted scientific research over the last forty years: the study of conversation across cultures, spatial cognition, pragmatics and language use, the psycholinguistics of language production, the evolution of language, and language diversity. I have trodden only lightly on my own and others’ work in linguistics, since this research is sometimes harder to compress and in any case lies partly to one side of the main argument. I am indebted to generations of graduate students and postdocs that made that work possible. We in the rich West often find ourselves very remote from the small, intensely networked communities of the sort that have characterized most of human prehistory. As an antidote I have been able to draw on my own first-hand experience of language use in small communities in Tamil Nadu, northern Australia, Mexico, and Papua New Guinea, and owe much to the many people who aided and abetted my fieldwork in those places. I also owe a tremendous amount to my colleagues at the Max Planck Institute for Psycholinguistics in Nijmegen, where most of the work was based, and to the many visitors and advisors we have had there over many years. This book was prodded into existence by an invitation to deliver a series of lectures at the Australian National University on this theme – in the event, I had to cancel the lectures, but my thanks to Nicholas Evans for the prod. I have benefitted from comments by a number of friends and colleagues on an early manuscript, including Asifa Majid, Rob Foley, Chris Hann, five anonymous reviewers, and CUP’s Helen Barton for which I am most grateful – I doubt I will have satisfied all their demands, but I have done my best. Thanks too to Ludy Cilissen for help with the figures.

Finally, thanks to Penelope Brown, my wife, who has shared many of the intellectual adventures and the travails of fieldwork.