There are several credible ranges of between 100 and 400 years between the flood and the tower of babel.

Let's look at the facts!

Fact: gestation period for a human is roughly 9 months
Fact: a human can easily have a baby every year during child bearing years
Fact: child bearing years last AT LEAST 20 years

So, year zero being the exiting of the Ark.

This is of course conservative, and doesn't take into account variables that can't be taken into account as this is a fact based look.

Noah and 3 sons and 4 wives have a child every year for 20 years. At year 20 then, there are a total of 80 children.

Since this is conservative, I'm waiting 20 years before reproducing any children from the children, ie the next set of child bearing children will be between the ages of 20 and 40.

So at year 40, those 80 children begin reproducing for 20 consecutive years. After 20 years of reproduction, those 80 children will turn into 800 children. This is year 60, and there are 800 children on top of the 80 and 4.

So at year 80, those 800 children who are now between the ages of 20 and 40 begin reproducing. This results in a population of 8,000 at year 100.

Sticking with the 20 year wait period. At year 120 those 8,000 begin reproducing resulting in 80,000 children of the ages of 20 - 40 at year 160.

So at year 200, there are 800,000 children who begin reproducing.

Resulting in 8 million children between the ages of 20 and 40 at year 240.

So at year 280 there are 80 million children between the ages of 20 and 40 able to reproduce, and at year 320 there are 800,000,000 who begin reproducing...

Leaving us at a tidy and fully factually possible sum, based on human genetics and child birth, at 8 BILLION PEOPLE ON THE PLANET 360 YEARS AFTER NOAH LEFT THE ARK.

Explain to me again why 8 billion people can't build a few pyramids of stone?

Look at facts instead of theories when questioning what is possible.