Smart phones seem to be directly linked to a worldwide crash in the birth rate.

It is “quite plausible that the modern digital media environment has had profound effects on society that have led to a decline in romantic coupling,” said Melissa Kearney, professor of economics at the University of Notre Dame. She has to talk that way, being an academic, but what she means is that people are doomscrolling, not copulating.

That’s old news, but the evidence for it is more impressive because it is data-based. That’s what we have social scientists for, and John Burn-Murdoch, a columnist with the Financial Times, realised that you could quantify the data if you talk to enough of them. So he did, and learned that the big drop in the birth rate happened precisely when people got smart phones.

Not every country adopted smart phones at the same time. 2007 was the year they were rolled out across the richer countries of the West, and by three years later 34 per cent of British people and 27 per cent of American people had one. Now it’s 95 per cent plus in both countries.

The birth rate was stable in countries like the US, the UK and Australia in the early 2000s, but in 2007 it started dropping in all those countries. If that was the only evidence, you could write it off as a coincidence or claim that it was due to a different cause, but the phones did not arrive everywhere at the same time.

They reached France and Poland two years after that, and middle-income countries like Mexico and Indonesia three years later (2012). They finally became commonplace in Africa in 2013-15 – and in every case there is a steep, permanent drop in the regional birth-rate at exactly that point.

That is a fact, which is easy enough to understand. Why it is happening is open to interpretation, but demographer Lyman Stone of the Institute for Family Studies points out that “To meet a person you’re going to marry requires filtering through a lot of people. If you socialise much less it takes you much longer to find a match, if you find one at all.”

That’s the key factor, in the view of Nathan Hudson and Hernan Moscoso-Boedo of the University of Cincinnati. Young people now are spending less time socialising with their peers in person than any preceding generation. In South Korea, which has the lowest birth-rate of all, young adult in-person socialising has halved in 20 years. Blame the phones.

In the midst of all this, most young men and women still report wanting two children. Moreover, women who do have children, at least in high-income countries, are having as many as ever. But a soaring number of women are having no children at all.

There are many other factors in play, of course: the unavailability/unaffordability of housing that forces many people in their 20s to live with their parents, the unrealistic expectations promoted by online influencers, even the growing scarcity of entry-level jobs. But the most persuasive (and irreversible) is phones, phones, phones.

So if that’s our future, at least for the next few generations, how do we cope with it? I won’t try to estimate what this dearth of children does to the sum of human happiness, but the practical effects of this change are clearly survivable.

There will be obviously be huge economic impacts: this will be the biggest collapse of demand that has occurred since the rise of capitalism and it will probably continue and intensify for many decades. It may reshape the concept of ‘family’ in ways just starting to become visible. And it will definitely kill the real estate market.

Moreover, it won’t help much with the climate crisis, because that is going non-linear right now. Population decline, by contrast, will just plod onwards in a predictable, linear and probably much slower rate. There will be much discomfort and some hardship as the populations drop, but it doesn’t feel like a looming Armageddon.

The world’s population was only one billion at the time of the American and French Revolutions, a little over 200 years ago. It had doubled to 2 billion by 1927, doubled again to 4 billion by 1974, and once again to 8 billion three years ago. And here’s the thing: at no point in this long climb did anyone look around and say “Why are there so few of us?”

All those enormously different population densities seemed entirely natural and normal to most of the people who lived in those eras. The natural world certainly felt the heavy impact of those numbers, but people not so much. With good management it needn’t feel any more disruptive on the way back down.

Gwynne Dyer’s latest book is Intervention Earth: Life-Saving Ideas from the World’s Climate Engineers