Humanity reached its first billion around 1800, after tens of thousands of years of history. On 15 November 2022, a symbolic date chosen by the UN, it passed 8 billion, just eleven years after reaching 7. The next billion should take longer, around fifteen years, a sign of the slowdown. These dates are estimates: censuses come with margins of error.
That's the estimate from a WHO-led study published in The Lancet in 2024, covering the half-century since the Expanded Programme on Immunization was launched in 1974. It works out to about six lives saved every minute, mostly infants. The measles vaccine alone accounts for around 60% of those lives.
According to the World Gold Council, about 216,000 tonnes of gold have been mined in all of human history. Because gold is so dense (19.3 tonnes per cubic metre), it would fit in a cube about 22 metres on each side, roughly the height of a seven-storey building. Strikingly, about two-thirds of it has been mined since 1950.