Towards the end of 2022, the human population on Earth is expected to reach

By Zaria Gorvett5th September 2022

Towards the end of 2022, the human population on Earth is expected to reach eight billion. To mark the occasion, BBC Future takes a look at one of the most controversial issues of our time. Are there too many of us? Or is this the wrong question?

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One moment, the valley was a tranquil, swampy wetland. Grasses and palm trees cast fuzzy shadows on the water below. Fish lurked warily at the edges of mangroves. Orangutans sought out fruit with leathery fingers. Then a dormant giant awoke from its sleep.

It was around 72,000 BC on the island of Sumatra, Indonesia. The Toba supervolcano was erupting, in what is thought to have been the greatest such event in the last 100,000 years. A series of thunderous explosions blasted out 9.5 quadrillion kilograms of ash, which billowed out in sky-darkening clouds that crept around 47km (29 miles) into the atmosphere.

In the aftermath, a vast area across Asia was blanketed in a layer of soft dust 3-10cm thick. It choked water sources and stuck to vegetation like cement – deposits from Toba have been found as far away as East Africa, 7,300km (4,536 miles) west of the eruption. But crucially, some scientists believe it plunged the world into a volcanic winter that lasted decades – and nearly made our species extinct.

Back in 1993, a team of American researchers studied the human genome for clues to its deep past, and discovered the tell-tale signature of a major “population bottleneck” – a moment when humanity shrank so drastically, all subsequent generations outside Africa were significantly more closely related.

Later studies have revealed that in this precarious era, which may have occurred between 50,000 and 100,000 years ago, our collective numbers may have hit as few as 10,000 people – equivalent to the current population of the sleepy settlement of Elkhorn in Wisconsin, or the number who attended a single drive-through wedding in Malaysia in 2020. The least affected part of the world was Africa, where genetic diversity remains high to this day – on this single continent, there are larger genetic differences between certain groups than there are between Africans and Europeans.