Population paradox: Why richer people have fewer kids (2024)

OVERPOPULATION is, arguably, the greatest challenge facing humanity. It took until 1800 for our numbers to reach 1 billion. Now the human population exceeds 7 billion and is set to reach 10 billion by 2085. Although problematic, it is also a testament to our success as a species. In a world in which people are increasingly well fed, healthy and safe, a population explosion is only to be expected. In fact, the surprising thing about human numbers is that they are not growing faster. Far from increasing rapidly as you might expect under such good conditions, human fertility rates are plummeting all over the planet. The question is, why?

An obvious answer is that access to contraception gives us control over our reproductive fate, allowing us to limit the number of children we have. But why we choose to do this is a puzzle for evolutionary biologists. After all, you are only alive to read this because you are descended from a long line of ancestors who were good at reproducing. When times were hard and resources scarce, they were the ones who successfully managed to pass their genes down to the next generation.

Today, survival is much easier for many of us, so why aren’t we taking the biological advantage and having lots of babies? Indeed, why do people in the richest parts of the world tend to have fewer children? And, given that some people do still choose to have large families, what will be the repercussions for the future of our species?

In traditional and developing societies, reproductive rates…