When I was in graduate school, one thing I often heard was that the goal of anthropology is to make the strange familiar and the familiar strange. I thought I knew what that meant,  but I didn't really understand it until the first time I conducted fieldwork. In my first year of graduate school, I traveled to South America to work with the Shuar, an indigenous population in the Ecuadorian Amazon. I was studying how children develop across different cultures. I had a number of expectations  for what that trip would be like. I knew I was going to get  a lot of bug bites - I did. I knew I'd ride a canoe down the winding rivers of the jungle - I did. And I knew I'd learn something I didn't know before - and I did. I learned what childhood was like in a small scale society. I saw independent young kids climbing trees to gather papayas when they were hungry. I saw them starting fires, preparing food for themselves and their siblings and even using machetes quite confidently, I might add. (Laughter) The thing I didn't expect was the culture shock of coming back to the United States. The strangeness of the Shuar was becoming more familiar to me, but suddenly, the familiarity of home started to feel strange. Being a child in a foraging society is very different than being a child in a Western society. In societies like the Shuar, children are much more independent  or as we like to call it "free-range." (Laughter) If you grew up in the era  before cellphones, that might be what your own childhood was like too. But for the newest generation of kids, this independance is quickly fading away. And that's because childhood has changed very recently and very rapidly. For virtually all of our time on this planet, for hundreds of thousands of years, our species lived in small bands of hunter-gatherers, more similar to how the Shuar live now  than how the average American lives. Then just a few thousand years ago, most of our environment started to change a lot. In fact, they changed  so quickly and so drastically that many anthropologists believe we are now in a state of evolutionary mismatch. This means that the environment has changed too quickly for some of our genes to keep up. Cultural evolution is much faster than genetic evolution. And what this means is that our minds and bodies might be optimized for a world that most of us no longer live in. So what did this past environment look like? Well, it's impossible to perfectly answer this question: bones fossilize, behavior doesn't. But we can learn a lot by looking at current day societies like the Shuar. And I want to clarify here: the Shuar are not a prehistoric people or windows into the past; they are modern people. But their way of life may give us a clue about what childhood was like in the past. And what we know from looking across a large number of these small-scale societies is that there are a lot of common patterns. For instance, in virtually all of these societies, women give natural birth, mothers breastfeed frequently and for long periods of time, parents sleep in the same room as their kids and children are constantly in physical contact with other people. These patterns have started to change in our Western societies: here C-sections are more prevalent, as is formula feeding. Kids often sleep in their own little rooms, and we don't want people in physical contact with us or our children. We value personal space. But let's go back to the idea of mismatch. The practices in yellow have marked the human experience for 99% of our time on this planet. The stuff in blue is just 1% of human history. These massive changes have happened so quickly that they may be out of whack with the world we are born expecting. And we think there are consequences for these changes, both good and bad. For instance, C-sections save lives, but they also shape the bacteria in our gut and our immune system in ways that might have negative consequences. But as an anthropoligst who studies behavior, one shared feature of these societies that I want to focus on and one that I've been able to see for myself is this: in small scale societies, alongside the adult community, is a complex mini-community of children, an alternate society. This child society is made up of kids of all ages and genders. It has its own unique culture and leaders. It has drama and a surprising amount of political intrigue. To understand why this child society is so important for development, it helps to keep in mind a curious fact about humans, and that is to become  a successful adult in any culture, children have to learn an enormous  number of complicated skills. These include both technical skills, like building a fire, and social skills, like maintaining friendships. And to perfect these skills, which take decades, children also develop foundational skills, like creativity, determination and problem solving. Like, one day, when the Shuar adults were playing a soccer game, I saw a group of kids set up their own  soccer game right next to the adults. When they called me over, I got really excited because I thought  they wanted me to play with them, but they were like, actually, you just keep score, so all of us can play. (Laughter) Problem solved. Shuar kids, like kids everywhere, spend a lot of time observing adults and incorporating their behaviors into their play. In fact, this is one of the reasons the play itself has evolved as a way to practice these skills in ways that are low-cost. No one has to encourage kids to do this. They do it on their own because through unstructured play, children learn how to become adults. Another important benefit to this mixed-age society is that kids teach to  and learn from one another. Younger kids benefit by learning from older kids who are only slightly better than them. And through teaching, older kids strengthen their own skills, as you may have experienced yourself - teaching helps you learn. It's hard to find these patterns in our Western societies. Kids here spend the majority of their development in a room with other kids their own age by design. Adults are totally in charge of the content and structure of their time. They determine when kids eat. They determine when kids play. They even determine when kids can go to the bathroom. And the unstrucutred play time of recess is now quickly becoming a structured activity. A strange byproduct of all this micro-managing is that we're teaching kids things that don't even need to be taught. Kids don't need to be taught how to play. They don't even need to be taught how to talk, really. You don't have to point to an apple and say, "This is an apple." Kids can also learn through exposure, like hearing you ask your husband for an apple and him handing you one. "Apples." - done. And the idea that it is a parent's duty to constantly craft and monitor their children's experiences causes a lot of unnecessary anxiety and may, in fact, be detrimental. When we take away mixed-aged play groups, when we take away unstructured play, we are in fact taking away the training wheels to adulthood that children have had for millennia. We are contributing to an increasingly mismatch environment. What's more, instead of letting kids develop foundational skills like problem solving, we're flipping to the back of the book to show them the answers. But that leaves them unprepared for all  the new problems they're going to face. This might be one of the reasons why the transition to college is so difficult for kids here, or why choosing a career path can feel so daunting. There's been very little space to explore. The lesson is not that we should go back to living like foragers or think whatever is natural is what we should do. That's the naturalistic fallacy. But we would benefit from taking a broader perspective and understanding how our evolutionary history has shaped the way our minds develop. We all want the best for our kids. We want them to be independent, confident, problem solvers. We want them to be happy. But paradoxically, our cultural practices in the West might be undermining children's abilities to develop these skills. It's hard to study the long-term consequences of these changes, especially because they're happening so quickly. But there are some tried-and-true methods to raising kids that we've been using for millennia. In fact, we've been using them for so long that children minds might actually be expecting them. Some of these methods you can start using now. Set up more mixed-age play dates for your kids. Give them the room they need to make mistakes. Give them more unstructured playtime. In fact, this is not just an idea that's relevant for those who are raising kids because even as adults, we are still developing. These lessons are applicable to you too. Allow yourself to make mistakes. Spend time with older family and younger friends. Give yourself some unstructured playtime. And perhaps recognize that the familiar culture all around you is, in fact, very strange. Thank you. (Applause)