The first paragraph doesn't make sense. If each person lived 100 years and there are 55 generations, then that would add up to 5500 years, not 17,000.
After reading that first paragraph again, what I think it says is that for 55 generations, they are 99% sure. That means that for the next period of time, from generation 56 on back, they are not as sure. So that could mean, and I think it does, that the 17000 years, is just a guess.
r
Generations are usually separated by 20 or 30 years, In earlier times probably even less. There could be any where between 3 to 5 generations within 100 years.
So with just a 20 yr separation average, it would take only 1100 years for 55 generations.
