email - November 2005
by Do-While Jones

Mutation Math

It is difficult to compute exactly how different two strands of DNA are.

We are going to comment on this email before you read it because, frankly, we are afraid you might not make it all the way through the email.

Math turns some people off. This is why we try to avoid using mathematical arguments whenever possible. But, in the October newsletter, where we talked about the published 4% difference between human DNA and chimp DNA, the devil made us do it.

Evolutionists were minimizing the difference between us and chimps to try to prove we have a close common ancestor. We wanted to show that the difference is really very large, and that one can present numbers in a variety of ways to minimize or maximize differences.

Doug argues that the differences are actually even larger than we said, and uses a mathematical argument to back up his position. We suspect most of you won’t be able to follow it. We present it to you primarily to show just how difficult it is to make sense of the numbers.


You might be interested in some explanations for some of the details related to the recent Newsletter.  They actually strengthen your case.

The 35 million substitutions represents ~1.25% of the genome.  The remaining 5 million indels are, on average, roughly fifteen bases long.  This means that there are about 75 million bases (i.e., ~2.75% of the entire genome) accounted for by these indels.  The sum of these is 4%.  Some of these indels are hundreds of bases long.  And many of them involve complex additions to the genome ( i.e., not simply the replication of an existing genomic neighborhood).  Note that such indels should NOT be treated as if they are a single mutation event.  For example:

abcdefghij <- original
abccccccdefghij <- single indel/single mutation
abcdefghdefghij <- single indel/single mutation
abcindeldefghij <- single indel/multiple mutations

… some information addressing another point you made on "Chimps Like Us":

"DNA contains the biological instructions for making proteins. If 29% of the proteins are identical, that means that 71% are different, doesn't it? If the DNA is 96% the same, why are 71% of the proteins it produces different?"

Suppose we have two "alignable" genomes (i.e., no indels).
Suppose that the chance of a single bp being different is 4% (i.e., 1 - 0.96).
Suppose that the chance of a single bp substitution effecting a change in protein is x.
Suppose that the average number of bp's coding a single protein are N.
Suppose that the chance of a protein being identical is 29%.

We have the following equation:
(1 - 0.04x)^N = 0.29

I expect that you follow.

Finally, you mistakenly think that "[in] the last 4,000 years of recorded human history, there would have been about 20,000 mutations."  In fact, the expected number of mutations would be proportional to the total number of humans born within the last 4,000 years!  Based on a stable pre-historic population size of one hundred thousand, we observe that the number of mutations experienced by that population in six million years is roughly the same as the number of mutations experienced by the historic human population in the last two thousand years (see In the first case, the population is compressed in size and expanded in time. In the second, it is compressed in time and expanded in size. Note, however, that the same number of mutations does not indicate the same degree of evolution. Evolution requires the "fixation" of those mutations, and it likely requires the accumulation of numerous mutations (i.e., sequential mutation-on-top-of-mutation).

cheers, Doug

(Incidentally, you might also want to correct the misattribution to Mark Twain:

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