The evolutionary numbers game

In my last post, I brought up how Michael Behe used the fact that 40,000 generations of E. coli were necessary for Richard Lenski’s experiment to find an E.coli who could utilize citrate. In this post, I am going to run through some numbers to show how 40,000 generations is nothing to evolutionary time.  Of course my numbers are going to be rough estimates, but I think it will get the job done.

For the sake of argument, lets say the earth is 10,000 years old (yes, people do believe the earth is this young). If Behe’s math is correct, then E. coli have 2,000 generations a year or 20,000,000 generations over the time of the young earth. More realistically, the earth is 4.5 billion years old, or nearly 10 trillion generations of E. coli. Of course E. coli hasn’t been around the whole time the earth has, but it does put that 40,000 number into perspective.

Let’s say that a beneficial mutation, such as the ability to use citrate, occurs once every 100,000 generations. Given the 10 trillion number above, that would give 100,000 beneficial mutations. Keeping in mind that E. coli only has ~5000 genes, each gene could have changed 20 times.

The last set of numbers we will be addressing is the nearly unfathomable number of bacteria on the planet.  For reference, our bodies alone are estimated to have 1,000 trillion or 10^15 of bacteria (not all E. coli of course) of bacteria (Yes, I know, it is kind of gross). There are over 6 billion people on earth bringing the total of bacteria inside humans to 6 X 10^24.

Now that is a lot of bacteria, just inside people, but how about all over the planet?  Bacteria are everywhere: inside us, on practically every surface, throughout the ocean, and throughout the earth.  It has been estimated that there are 5 X 10^30 bacteria on earth.

10^12 generations of bacteria and 10^30 bacteria.  Those are mind-boggling numbers!  I know the numbers don’t really mean too much by themselves, but just keep them in mind when an IDer tries to convince you that something like 40,000 generations is a big deal.

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One Response

  1. Not to mention, the IDrs probably aren’t mentioning (or don’t understand) the fact that several independent mutations were required for citrate utilization, not just one.

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