The well-established genetic equidistance result shows that sister species are approximately equidistant to a
simpler outgroup as measured by DNA or protein dissimilarity. The equidistance result is the most direct
evidence, and remains the only evidence, for the constant mutation rate interpretation of this result, known as
the molecular clock. However, data independent of the equidistance result have steadily accumulated in recent
years that often violate a constant mutation rate. Many have automatically inferred non-equidistance whenever
a non-constant mutation rate was observed, based on the unproven assumption that the equidistance result is an
outcome of constant mutation rate. Here it is shown that the equidistance result remains valid even when
different species can be independently shown to have different mutation rates. A random sampling of 50 proteins
shows that nearly all proteins display the equidistance result despite the fact that many proteins have nonconstant
mutation rates. Therefore, the genetic equidistance result does not necessarily mean a constant mutation
rate. Observations of different mutation rates do not invalidate the genetic equidistance result. New ideas
are needed to explain the genetic equidistance result that must grant different mutation rates to different species
and must be independently testable. |