Counting Critters

This picture allows us to set a lower bound on the number
of creatures that ever lived of ~4.

We recently had a big book sale [1] here in town where books were being sold for about a quarter.  Needless to say, I bought far more than I'll probably ever need or read.  One of the books I bought was called General Paleontology by A. Brouwer [2].

Anyways, I didn't really make it too far in the book.  In fact, I only made it to the first sentence of the second paragraph of the first chapter, when I encountered this line:

"The number of individuals which has populated the Earth since life began is beyond estimation."


Horse feathers, I say!  Horse Feathers!

The number of things that ever lived may very well be unknowable, but it's certainly not beyond estimation.  So below, Alemi and I each provide an estimate for the total number of creatures that have ever lived on Earth.