I was just talking about this today. The world population just ticked over 8 billion, and India has surpassed China as the most populous nation. What I find amazing is that in the 1950s the world population was about 2.5 billion. Within living memory we have gone from 2.5 to 8 billion human beings.

More interesting facts. If you add up every animal on Earth, all of the wild animal biomass (mammals only) in the ocean adds up to about 2%, and everything on land is another 2%. Humans make up 34% of the biomass, and livestock makes up 62%. There's a reason Bill Gates has been buying up so much farmland that he is now the largest private owner in the US. As people get richer they eat more meat, and there are going to be a lot more people demanding high quality protein every year. There is going to be a lot of money to be made as demand outstrips supply.

If you have an hour to burn, this is a great video on exponential increases.