8 billion people

We never know precisely how many of us are alive at any one time, but this Tuesday is the United Nations’ best estimate on when we’ll reach 8 billion human beings.

Eight billion. It’s a number too big to imagine but think of it this way: In the time it takes you to read this paragraph, the world’s population grew by around 20 people.

While the Earth’s population is growing quickly, the growth rate is starting to slow down. Eventually, it will start falling and our societies will shrink.

Humanity is changing day by day in ways we can’t perceive over short periods, but in ways that will reshape our world over the coming century.

We’ve come a long way, fast  

Homo sapiens have roamed the Earth for roughly 300,000 years, give or take (no one left a diary back then). 

We evolved to have big brains and long legs, but our population grew relatively slowly at first.

There were perhaps 230 million of us on Earth at around the time of Cleopatra’s death, as the ancient Egyptian civilisation came to an end.

The population had more than doubled by the Renaissance in 1500 and doubled again by 1805 when the ancient Egyptian civilisation was being rediscovered with the help of the Rosetta Stone.

These are all pretty rough estimates — we didn’t have comprehensive censuses in the Middle Ages – but the human population has been on a slow burn, until recent centuries, when it has boomed.

The 2 billion mark was reached just before the Great Depression in 1925, and it took just 35 years from there to get to the third billion. 

Since then, the population has been rising by another billion every 10 to 15 years.

Where are we going?

The world is likely to have a couple more billion mouths to feed in just a few decades.

The UN’s latest projections, released earlier this year, suggest the world will house about 9.7 billion humans in 2050.

“Demographic projections are highly accurate, and it has to do with the fact that most of the people who will be alive in 30 years have already been born,” the UN’s population division director, John Willmoth, says.

“But when you start getting 70, 80 years down the road, there’s much more uncertainty.”

Under its most likely scenario, the UN projects the world population will reach about 10.4 billion in the 2080s.

From there, it’s set to plateau for a couple of decades, before falling around the turn of the 22nd century.

But the range of reasonable possibilities in 2100 is considerably wider, between 8.9 and 12.4 billion.