Frank Tipler, the Professor of Mathematical Physics at Tulane, did a little digging and found a claim by Richard Lenski to have observed fixation in a virus taking place 10 times faster than he observed in his famous experiments with E. coli bacteria.
It occurred to me that the fastest rate of genetic fixation should occur in viruses, since they are the least complicated organisms that be considered “living.”
Here’s a post by Richard Lenski, in which he SEEMS to claim that his students observed fixation of a group of four mutations in the Lambda virus in 8 days. The life cycle of the Lambda virus is 45 minutes, so 8 X 24 X 60/45 = 256 generations. In a replication experiment with a larger population, he SEEMS to say it took 3 weeks, or 21 X 24 X 60/45 = 672 generations.
Either is faster that Lenski’s E. coli fixation time of 1,600 generations per mutation.
But since there are 4 mutations fixed, we have, for each mutation, an even faster rate: 256/4 = 64 generations per individual mutation, or 672/4 = 168 generations per individual mutation. Lenski argues for strong selection pressure to account for the rapid rate.
I think that these numbers would be the true fastest observed mutation fixation rate. Still too slow to account for the human-chimp fixed gene difference in 9 million years.
Duly noted and much appreciated. Just to keep things in perspective, while this faster observed rate theoretically reduces the minimum number of years per fixed mutation from 32,000 to 3,360, that only increases the maximum number of fixed mutations since the Last Chimp Human Common Ancestor to 2,679, which is still considerably short of the observed 15,000,000 fixations required.