As I understand it, he's concerned about a world where a large elder population is supported by a much smaller younger population. Not only does this put a strain on younger people, but it means that the pool of people who are at the top of their game as far as being innovative and productive is smaller. And that being said, I think we need to use some of our innovation to figure out how to make that work in spite of any potential challenges because that's going to be easier than figuring out how to have the earth sustain an ever increasing population.