You know the story. Despite technologies, regulations, and policies to make humanity less of a strain on the earth, people just won’t stop reproducing. By 2050 there will be 9 billion carbon-burning, plastic-polluting, calorie-consuming people on the planet. By 2100, that number will balloon to 11 billion, pushing society into a Soylent Green scenario. Such dire population predictions aren’t the stuff of sci-fi; those numbers come from one of the most trusted world authorities, the United Nations.

But what if they’re wrong? Not like, off by a rounding error, but like totally, completely goofed?

That’s the conclusion Canadian journalist John Ibbitson and political scientist Darrell Bricker come to in their newest book, Empty Planet, due out February 5th. After painstakingly breaking down the numbers for themselves, the pair arrived at a drastically different prediction for the future of the human species. “In roughly three decades, the global population will begin to decline,” they write. “Once that decline begins, it will never end.”

Buy EMPTY PLANET on Amazon. Penguin Random House

But Empty Planet is not a book about statistics so much as it is about what’s driving the choices people are making during the fastest period of change in human history. Ibbitson and Bricker take their readers inside the Indian slums of Delhi and the operating rooms of Sao Paulo, Brazil, to eavesdrop on the conversations young professionals have at dinner parties in Brussels and over drinks at a young professionals’ club in Nairobi. The end result is a compelling challenge to long-entrenched demography dogma, Trojan Horse-d inside an accessible, vivid portrait of modern families from every walk of life. The authors sat for an interview about how they arrived at a radical new outlook on the human race and its implications for future societies.

WIRED: The UN is a well-regarded authority on everything from public health to food security and global economics. What made you think that they were getting population growth wrong?

Megan Molteni covers genetic technology, medicine, and sharks for WIRED.

JI: The UN population data is something we call vertical knowledge, or “everybody knows” knowledge. Whether it’s the prime minister of a country, a university academic, a business leader, a student, just a guy on the street, you ask any of them, “What is happening with population?” and they go, “Oh it’s terrible, there’s a huge population explosion. I was just watching a movie last night where Earth got so crowded everyone had to relocate to the moons of Jupiter.” It’s just deeply embedded.

DB: And whenever that happens you should really go and look hard at the assumptions, and test them yourself, because most of the time reality has already moved past where that vertical knowledge resides.

JI: So that’s what we did. And it didn’t take long before we realized that there was a whole body of demographers who have been questioning the UN’s numbers for years. They’ve just been talking to each other at conferences and through scholarly articles, but they’ve never gotten this information before the general public. That was kind of our starting point. And then when we went out and talked to real people in the world about the choices they’re making, that’s when the statistics we were seeing came to life.

You traveled all over the globe to interview people for this book. What’s one image or conversation that really made the statistics jump off the page?

DB: There was a moment when we were sitting in this little school in Srinivaspuri, listening to a focus group of 13 or 14 women who lived there. And I kept seeing this faint glow light up under their saris. I didn’t know what it was. And then I saw one woman reach in and pull out a smartphone, look at it, and put it back. And I realized, here we are in a slum in Delhi, and all these women have smartphones. Who can read. Who have data packages. And I was thinking, they have all of human knowledge in their hands now. What’s the impact of that going to be?