How much mutation is too much?
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Anzai, 2003). This brings our actual mutation count per person per generation up to about 204 - 636. But if we factor in the fact that macro-mutations can change 3-10-fold more nucleotides than all point mutations combined, our final tally of nucleotide changes per person could come up to as high as 612-6,360 per person per generation! These numbers are mind-boggling! Yet even these numbers may still be too low - we have not yet considered inversions and translocations. Furthermore, evolutionary theorists are now invoking extremely high inter-genic conversion rates, which could double these numbers again. Wow! Do you recall the beginning of this chapter, where we learned that the famous geneticist Muller considered that a human mutation rate of 0.5 per person or higher, would doom man to rapid genetic degeneration? Although we do not know the precise human mutation rate, there is good reason to believe that there are more than 1,000 nucleotide changes in every person, every generation (see Table 1). To be exceedingly generous, for the rest of this book I will use the most conservative number being referred to in the literature today - ‘just’ 100 mutations per person per generation (except where otherwise specified). However, please note that this is only a fraction of the true number, and this number excludes the most destructive classes of mutations. Of all these mutations - what percent are truly neutral? In the last few years there has been a dramatic shift in the perceived functionality of most components of the genome. The concept of “junk DNA” is quickly disappearing. In fact, it is the “junk DNA” (non-protein-coding DNA), which appears to be key to encoding biological complexity (Taft and Mattick, 2003). The recent Taft and Mattick study strongly suggest that the more “junk” - the more advanced is the organism. So mutations within “junk DNA” can hardly be assumed to be neutral!