The world’s population has surged past eight billion.
It comes just 11 years after the total hit seven billion amid an increase in longer lifespans.
However, the hike in people poses challenges on food, water and energy resources as a peak of 10.4 billion is forecast in the 2080s.
UN population expert John Wilmoth said: “It raises questions about our impact on the world.”
But the “unprecedented growth” is slowing and there will not be nine billion people until 2037. It comes as 37 million people face starvation in the Horn of Africa, including Ethiopia, after four droughts amid climate change.
India is now drawing level with China, which has the biggest population of 1.4 billion, and is due to surpass it next year.
In the book 8 Billion And Counting, Jennifer Sciubba says in AD1 there were 300 million people and women had four kids on average.
She added those alive today “represent about seven per cent of 108 billion who have ever taken a breath”.