Currently the world's population doubles about every 40 years. But lets be conservative and say it doubles every 150 years. You would get a population of 8 billion people in just 4800 years(32 doublings). With the Flood being about 4500 years ago that lines up perfect with today's 6.5 billion people. (this includes war and disease).

If we assume that humans have been around for 50,000 years (evolution teaches much longer then that) and if we were to use the calculations above, there would have been 332 doublings, and the world’s population would be a staggering figure—a one followed by 100 zeros; that is

10,000,000,000,000,000,000,000,000,000,000,
000,000,000,000,000,000,000,000,000,000,
000,000,000,000,000,000,000,000,000,000,
000,000,000.