Until the end of the 19th Century the earth’s population was relatively stable. We entered the 20th century with around 1.5 billion people. And although women were having a lot of babies the average survival rate was only 2.1 children per woman. But then conditions improved and Europe experienced a population explosion as women continued to have lots of children and they survived. However within 2 generations the birth rate had dropped and we’re back to around 2.1 children per woman.
And this is a pattern we can see all over the world – female fecundity is high and survival rates are low keeping the population stable, then as conditions improve and survival rates increase, the population explodes, but within two generations the birth rate has dropped right back, stabilising the population again.
This means that probably around 2050 we’ll see the global population plateau, so does this mean we should stop worrying about the current population explosion and could it even mean that come 2050 we’ll start to see the population begin the decrease?
Professor Sir David King is from the Smith School of Enterprise and the Environment at Oxford University and is the ex Chief Scientific Advisor to the Government