I need a formula for the following - hopefully this isn't much of a challenge, but I can't figure it out! lol

It's regarding a peice i'm doing on our population since the beginning(well christian beginning anyway)

Population went from two -> 6.83 billion(current) The christians believe the earth is only around 6,000 yrs old... so working on the average generation lasting 80yrs, thats 75 generations since Adam & Eve

I want to find out what percentage or number each generation has to grow in order to reach our current population.

With the data, I hope to estimate the total population of people who have lived & died + the current population since adam & eve...