>I’m going to try to win the award for the most controversial theory on this thread.
Extremely easy to beat that.
You can see that global population used to stay at around half a billion until around 1700. The growth is a recent thing.
So let me propose a more controversial theory - lead made people have a lot of children.
You can't beat this.
Lead? Lead was used for millenia. The Romans made copious use of lead.