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.
Even that doesn't work.
Considering life expectancy, normal human breeding patterns....
If everyone had kids by 25, you would have kids, grandkids, great grand kids, and great-great-great kids just before you die. (Some birthed at 24)
That would be 4 generations created in 100 years, 5 if your line is young breeder and you were born inside that span.
