I know, right? The guessing game involved in this makes it amazing that our ancestors had like 8-12 kids a piece. How?
Well the first couple I can understand. They had nothing better to do and probably had more sex... but by like #4 or 5? Knowing the odds of getting pregnant, and the assumed lack of time to have sex at all? Yeah, dumbfounding!
I guess they also started when they were 12, too, and were much more fertile.