So Many Critters

Suppose you started with one self-replicating life form. It’s a really, really slow moving life form, but it’s capable of reproducing. After literally forty million years, it’s finally able to double, and now there are two critters.

Another forty million years go by, and now those two critters multiply by two… only that’s not quite what happens, because some of them die off and then are replaced by others, and so on. The important thing to know is that at the end of that second forty million year period, there are now four critters, whereas there were two of them forty million years ago, and one of them eighty million years ago.

This happens again, as another forty million years go by. Lots of critters are being born and dying, but the population is eventually able to stabilize, and now there are eight critters.

Lather, rinse, repeat. How many critters do you have after four billion years?

Before you answer, and assuming you’re not already doing the math in your head, let’s consider t…