With Dr. Fenner approaching 100 years, that is a good number to work with.

I know, as my wife and I get older, this new generation just do not know what they are doing. Probably the same thing my parents generation thought about mine, and his before that....
Life is fagile on our planet, many things can happen to eliminate humanity. There have been many programs showing how this can happen, from metors to disease. But world population will just trim down the population until there is enough to feed. Not pleasant, just look at some of the less developed countries to see how badly it can be handled, but not a humanity ender.