The New Haven home of Daniel Colón-Ramos, Ph.D., his wife, Emily Wang, M.D., assistant professor of medicine, and their triplet daughters is a Tower of Babel. The 4-year-olds Alexandra, Beatriz, and Caysani speak Spanish among themselves, with their dad, and with their nanny, and speak Mandarin with their mom. Mom and Dad speak to each other in English, and each speaks a bit of the other’s native tongue. Watching how his daughters play and communicate led Colón-Ramos, associate professor of cell biology, to write an article for the TEDBlog in December 2012, when the girls were toddlers. In “On nature versus nature: A neuroscientist knee-deep in diapers reflects,” he described the lessons he’s learned from his daughters, how they’ve changed his brain, and the futility of the debate over nature versus nurture. Since he wrote the article, Colón-Ramos tells us, what he said then remains true today.

I couldn’t have designed a better experiment if I’d tried. I am a neuroscientist and I am the father of 2-year-old triplets—two identical and one fraternal. As a professor at Yale University, I spend most of my time designing experiments, researching or teaching about the brain and the nervous system. The rest of my time I spend surrounded by my three daughters. To understand the dynamics in my household, think terrible-twos, and then cube it.

In the quiet sanctity of my lab, we study how the nervous system forms during development. In all animals, from humans to the tiny worms that we use for our experiments, neurons connect to each other and form circuits that underlie behaviors. Genes (made of DNA) underpin many aspects of development—from how our brain forms to the color of our eyes.

My identical twin daughters look identical because they share all of their DNA; they are essentially clones of each other. They teethed exactly the same day, and their funky hairstyle is not the result of a visit to a stylist, but of genetics. Their personalities, however, are not identical. Not even close. The twins’ personalities, which share 100 percent of their DNA, are curiously more similar to that of their fraternal sister than to each other.

That certainly came as a surprise to me. After all, argue all you want about nurture, but behaviors do have genetic underpinnings in the animal kingdom. Take reptiles; soon after hatching from its egg, a baby crocodile can hunt dragonflies with the same dexterity that its parents can hunt antelopes. Who taught the baby crocodile to hunt? Genes.

I reflected about this a lot as I held my newborn daughters in the nursery room of the hospital. Human brains at birth do not appear nearly as impressive as a reptilian brain. For crying out loud, the tiny nematodes we use in the lab for our experiments can move around better at birth than a human baby! Newborns appear as blank slates. Are we really a tabula rasa? What are the roles of nature (genes) and nurture (our environment) in the development of our brains, in making us human?

My epiphany came with the first visit to the pediatrician. She closely monitored our daughters as they met, in unison, one developmental milestone after the other. As a neuroscientist, I knew what this timely emergence of complex behaviors meant: it is a hallmark of preprogrammed brains. But our preprogrammed brains are not for hunting dragonflies. The evolutionary pressures that have shaped our brains are different from those that have shaped the brains of swamp-bound reptiles.

We are born into complex societies and quickly have to learn to negotiate our place within them. My three kids, the ones playing with my iPhone, are the same species as my ancestors, who 40,000 years ago were figuring out how to sharpen a rock and fit it into a spear. The Homo sapiens brain is wired in a very particular way: to allow us to connect to other human brains.

Our home is testament—a cross between the Tower of Babel and a Univisión soap opera. It is filled with sound, from the tonal Chinese my wife has taught the triplets to the slurred Puerto Rican Spanish they have learned from me. During the past two years I have witnessed how each of my daughters has masterfully decoded the complex rules of language and social interactions in three very different and overlapping cultural contexts, and simultaneously. They confidently navigate between languages in a way that sometimes neither my wife nor I can follow. Chatty conversation and festive giggles are only one disagreement away from despair and temper tantrums over a train set, a Crayola, or a dinosaur shirt. But most meltdowns end with hugs, sometimes all three at the same time, as they can’t wait to make up.

My daughters’ desire to connect is not just cute, it’s a matter of survival. So important is our need to connect to other human brains that extreme cases of child neglect have resulted in developmental problems not unlike those seen for mental retardation. These extreme cases tell us something profound about the brain. It tells us that even in cases in which normal genetics prime the brain to connect to other brains, the absence of human input cripples brain development. Our brains need other brains to develop properly.

These seemingly delirious thoughts of a sleep-deprived scientist are neither new nor original ideas. Today it is broadly accepted that trying to separate nature from nurture is as asinine as trying to debate whether a cake is made out of milk or flour. But this is important beyond a mere academic debate. In science, extreme cases are used to understand concepts. If no human contact during critical developmental periods can cripple brain development, what are the consequences of reduced stimulation due to a defective and underfunded educational system? The United States incarcerates more of its youth than any other country in the world—what are the consequences of growing up in a prison? We are social and codependent animals—what are the hidden costs to our society when we ignore the “nurture” part of the human development equation?

The human brain has over 100 billion neurons—there are more neurons in a single human brain than stars in the Milky Way. When a parent stares at the lost, unfocused gaze of a newborn child, they are literally staring at a constellation of possibilities, at a brain primed through evolution to connect to other brains, to devour information, to adapt and to reach its potential. In truth, I’m highly trained, but not that special; we are all born scientists, and our brains are molded by our favorite subjects of study, other humans. And I have the perfect experiment to prove that—my brain, which has been transformed by my daughters.