The questions that kids ask about science aren’t always easy to answer. Sometimes, their little brains can lead to big places that adults forget to explore. That is what inspired our series Science Question From A Toddler, which uses kids’ curiosity as a jumping-off point to investigate the scientific wonders that adults don’t even think to ask about. The answers are for adults, but they wouldn’t be possible without the wonder that only a child can bring. I want the toddlers in your life to be a part of it! Send me their science questions, and they may serve as the inspiration for a column. And now, our toddler …

Q: Who invented houses? — Micah B., age 4

It’s possible that people have been living in houses since before there were technically people. The oldest archaeological evidence of house construction comes from the famous Oldupai Gorge (also called Olduvai Gorge) site in Tanzania, and the structure is around 1.8 million years old. Nobody knows exactly which proto-human species is responsible for the tools (and houses) found at Oldupai. But, whoever they were, they predate the modern human species as we know it by a solid one and a half million years.

But houses, it turns out, are complicated. They’re more than just the walls around us or the roof over our heads. Houses teach us about what people believe, who they are, and even what their health is like.

Let’s start with that ancient one. A house that’s 1.8 million years old is not exactly in turnkey condition. We are talking about a circle of stone surrounding a slightly sunken spot of earth. It’s about 13 feet in diameter and, in many ways, resembles the foundations of grass or stick huts still being built by hunter-gatherers in other parts of the world today.

But not everybody buys that these circles are the world’s oldest houses, said Peter Peregrine, professor of anthropology at Lawrence University. For one thing, those rocks could have gotten into that same position purely by accident, pushed outward by the expanding girth of a growing tree that left the stones behind when it died. Also, even if proto-humans did put those stones there and build something on top of them, not all archaeologists are willing to count it as a house. Instead, he said, some of the oldest houses that everybody agrees are houses show up in places like Terra Amata, in Nice, France — a 400,000-year-old site where researchers can find carefully dug postholes and the remnants of cooking fires, as well as piles of stones that once served as foundations.

So, what is a house? Given how much time we all spend with houses, it’s a little embarrassing to admit that we have no solid definition to work from. Is a temporary shelter from the sun a house? Is a house a house if it is actually a cave? Are tents houses? It’s hard to identify the earliest houses both because (as at Oldupai) the structures were probably made out of materials that didn’t preserve well and because (again, as at Oldupai) it’s debatable whether those structures were houses at all. And what about animal abodes, do those count as houses? Jerry Moore, professor of anthropology at California State University Dominguez Hills and author of “The Prehistory of Home,” pointed out that lots of animals — from birds to chimpanzees — make things that could be called houses. But we don’t count any of those creatures as the first house-builders.

Instead, what he thinks really sets a human house apart — what makes a house a home — is the culture we layer on top of the architecture. “Only humans, that we know of, have the a concept of ‘home’ where there are so many values associated with that place,” he told me.

And those values, the way we live, seem to be reflected in what we build. “If you find a round house, there’s a very good chance those people are at least semi-nomadic,” Peregrine said. “If you find a square house, those people are likely sedentary.” Compare those ancient structures at Terra Amata, which seem to have had rounded walls, with the squared-off, mud-brick buildings of Çatalhöyük, a 9,000-year-old permanent settlement being excavated in Turkey. Nobody knows exactly why that difference in architecture exists, he told me. But it’s a strong pattern, holding true all over the world. And archaeologists use it to make assumptions about the people who built ancient houses.

You can also learn about the way social relationships were structured in a community by looking at its houses, said Carol Ember, president of the Human Relations Area Files at Yale, a comparative cultural anthropology database. Studying living people over the past 150 years or so has taught us that larger houses are strongly associated with what anthropologists call “matrilocal residence” — cultures where, basically, when a man and woman get married, he goes to live with or near her family. The average house for a matrilocal society has a living area that’s more than six times the average size of a patrilocal house — where a woman goes to live with or near her husband’s family. The basic explanation for this is pretty simple: Matrilocal societies usually involve sisters, and their families, sharing a home and resources. Brothers don’t seem to do that in patrilocal communities.

Studying buildings to learn about people doesn’t just work for traditional cultures and ancient ruins. Our houses tell stories about us today, too. There are documented health outcomes associated with different kinds of housing: People who live in mobile homes tend to show patterns of more disturbed and less healthy sleep; apartments built after 1969 are associated with higher levels of depression, as are buildings where residents lack private yards and apartments where occupants’ front doors open onto a long, shared outdoor deck; the type of emergency housing a person lives in after a natural disaster is correlated with alcohol consumption patterns. There’s a lot you can learn about the social structure of, say, Los Angeles — from economic systems to social inequality — by looking at the differences between the largest and smallest homes, Moore said.

Whoever invented the house invented more than a building — it was an expression of culture that was shaped by the way people lived, and it shaped our lives in turn. Houses are, as Moore put it, “part of the consultable record of what it means to be human.”

So, with that in mind, go clean your room. You never know when an anthropologist might show up.