What’s up Cuz
July 3rd, 2006Er, wow: Roots of human family tree are shallow
The math is so obvious I never thought about it:
It’s simple math. Every person has two parents, four grandparents and eight great-grandparents. Keep doubling back through the generations — 16, 32, 64, 128 — and within a few hundred years you have thousands of ancestors.
It’s nothing more than exponential growth combined with the facts of life. By the 15th century you’ve got a million ancestors. By the 13th you’ve got a billion. Sometime around the 9th century — just 40 generations ago — the number tops a trillion.
But wait. How could anybody — much less everybody — alive today have had a trillion ancestors living during the 9th century?
The answer is, they didn’t.