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Agustín Fuentes, a Professor of Anthropology at Princeton University, focuses on the biosocial, delving into the entanglement of biological systems with the social and cultural lives of humans, our ancestors, and a few of the other animals with whom humanity shares close relations.

What is the capacity for belief in humans, and how does it shape our lives and interactions with the world? According to Agustín Fuentes, a professor of anthropology at Princeton University and author of Why We Believe: Evolution and the Human Way of Being, the human capacity for belief is the most significant trait that sets us apart from other animals.

This capacity for belief, which importantly is not limited to religious belief, allows us to take our experiences and turn them into perceptions, ideologies, and lifestyles to which we can fully commit — thereby shaping our reality and the reality of future generations.

At its core, Fuentes explains, human belief is rooted in, and contingent on, our evolutionary history. Unlike other mammals, human infants are born with brains that are just 40% of their adult size. This extended childhood allows for constant social and environmental influence, which become the fabric of our being. Beliefs even influence our biological make-up, from our gut microbiome to our hormones.

Agustín Fuentes: You know, one might wonder when thinking about human evolution, why are humans so complicated? Why are our cultures so messy? What's the point of all this? Why don't we just run around and find food and have sex and you know, try not to die? Well, actually, most things do more than just run around, find food, have sex, and try not to die. But humans do a lot more than that. We make our running around, finding food, having sex, and trying not to die really complicated with all these cultural sort of historical, political things. One might ask: was there a reason for this? In our evolutionary history, was there a point where our evolutionary trajectory was like, "Okay, you know what? You need to make your lives much more complicated to be able to succeed." The simple answer is no, we didn't need to do that. That's not the way evolution works. 

My name is Agustín Fuentes. I'm a Professor of Anthropology at Princeton University, and my most recent book is "Why We Believe: Evolution and the Human Way of Being." For anyone who's spent any time around a very young infant, something strikes you compared to the rest of the world: Human infants really can't do very much for themselves. A baby giraffe is born and you know, in a couple hours, it's off, it's running. Human infants-nothing. They're just laying there. Why are human infants like this? One of the critical reasons, evolutionarily speaking, is because it takes so long for the human brain to develop. So it turns out, that unlike almost all other mammals, our brain, when we're born, it's only about 40% of its adult size. So, the human brain develops in the world outside the womb. This really long childhood means that our brains are always social, always in this dynamic with other humans, with other animals, and the environment. And in fact, that environment becomes part of who we are. 

So humans are particularly distinctive, right? We have these giant brains that develop mostly after we're born. That allows us to do some stuff that I think is not seen in other animals- and one of those is this incredible human capacity for belief. That is, this ability for humans to take our experiences, our imaginations, and put them together into ideas, or ideologies, or perceptions- and commit to them. Commit to a perception or idea or a person or a thing so fully, that it becomes our reality. If I pulled out a $20 bill, most people in the world would be like, "I know what that that is. I know what that means." It means something, 'cause we all believe it means something. This is a piece of paper! And yet, all of us have this capacity to invest so fully to make it a fact; real in the world.

And this thing, it doesn't have to be tangible, it doesn't have to be material. Humans can look at the world, imagine something wholly new, and try to make it a reality. For me, what's really amazing about belief is that biologically, what we believe about the world shapes the way our bodies respond to it. Our hormones, our neurons, our muscles, the enzymes in our microbiome in our guts actually respond to the way in which we believe the world is and how that affects us. So usually when I talk about belief, people immediately go to religion. Their first thought is: "Oh, belief. It's a faith tradition, a theology. It's a ritual." Like yes, religion and religiousness obviously need belief. That's a central part of it. But what people don't understand, or don't think about, is that this capacity for belief, that's actually much older. We are so complex that things like culture and history and belief systems, they enable us to live day-to-day without just losing our minds. 

Imagine if every time you wake up, you had to be like, "Okay, who am I related to? Who do I like? Who do I not like? What should I clothe myself in? What should I eat? How should I walk? Where should I go? What's going on?" We have beliefs, we have traditions, we have structures, just like all animals, but ours are extremely complicated. But what's really challenging then, is why do we believe what we believe? Why do we believe what we believe is not a straightforward answer, because it has to do with who do we grow up with? Most people say, "You are what you eat," but in reality, you are who you meet. We are shaped as our brains grow, as we interact. Our worlds are structured by our social realities and our ecological landscapes. Those inputs shape who we are, and how we see the world. So the most amazing thing about belief is that it enables us to create cultural complexity, ideologies, traditions, and rituals, and make them real for us.

The problem with that is some of these rituals, traditions, beliefs, are in conflict with other people's rituals, traditions, and beliefs. And these different beliefs, because they're real for the people who hold them, can lead to incredible conflict sometimes. And when we think about contemporary political issues, economic issues, when we think about race and racism, sex and gender-people's beliefs are real for them. They're frequently structured by their culture, their history-but they're real. If you think about the world right now, there are many wars, incredible suffering, unbelievable inequity. A lot of that has to do with history, with politics, and with economic structures, but it is also equally due to the beliefs, the perceptions of different groups of people, about how the world is, and how they want it to be. And that's the challenge for the future. Can we bring together science, belief, tradition, imagination, and creativity in such a way that we can ensure at least a little bit more harmony?