There is a self-evident inverse relationship between genetic diversity (measured by point mutations) and organismal or epigenetic complexity (roughly measured by the number of cell types or epigenetic molecules) (1, 2). Humans have the largest number of cell types due to their intelligent brain (a single neuron could represent a unique cell type) among all life forms and are therefore expected to show lowest genetic diversity and morphological diversity for phenotypes that are susceptible to modulation by random point mutations. Body height could be one such phenotype.

In contrast, for phenotypes that are not or less susceptible to random mutations, we would not necessarily expect low diversity. Such phenotypes are determined in complex ways and hence naturally more sensitive to destruction by randomness. Indeed, human mind phenotype is obviously determined in complex ways and is extremely diverse with each one of the 6 billion people on Earth having a unique mind. Since a mind phenotype has nothing random to it (think about its capability to do precise mathematical reasoning), random mutation could only be expected to impair the mind. The more complex and precise the way in constructing a phenotype, the more susceptible it is to destruction by randomness. We simply cannot expect randomness or random mutation to be of benefit to the precise mind, which has the phenotype of intention, purpose, and goal, all complete opposites of randomness. So, how is the extreme diversity of human minds achieved without relying on random mutations or high genetic diversity?

Well, recombination of fixed modules or gene units could easily achieve it. Think about the infinite number of music pieces that could be accomplished by the infinite number of ways of combining the basic 7 notes of music. To achieve phenotypic diversity by combinations of immutable genetic units is epigenetics and is a higher level/form of achieving phenotypic diversity. This advanced way of achieving phenotypic diversity is not possible if the genetic units are easily mutated. Humans represent the pinnacle of high phenotype diversity by way of combinations of immutable genetic units. Such diversity in terms of human creativity and thoughts is infinitely high, which is only made possible by restricting random mutation/genetic diversity and by relying instead on combinatorial rearrangements of fixed genetic units. Even if humans can exist forever, there is no possibility of my mind today being exactly copied by a human mind in the future.

References:

1. Huang, S. (2008) Histone methylation and the initiation of cancer. Cancer Epigenetics, Ed. Tollefsbol, T., CRC Books.

2. Huang, S. (2009) Inverse relationship between genetic diversity and epigenetic complexity, submitted. Preprint available http://precedings.nature....