Fibonacci would just count the number of females and conclude that the population rate would be exponential with the base being the golden ratio, and the time intervals would be some constant "generation". Not a good model, but it does have the value of being easy to solve.
Which, I guess, makes it a good model.
We have 300,000,000 in the USoA now.
I'll bet the Indians sure didn't expect THAT when them 3 boats first landed, just over 500 years ago!!