Abstract :
Elsewhere, it is argued that intelligence could not be both a heritable trait and one that has made an important contribution to fitness because fitness related traits usually show low heritability. However, pleitropy and balancing selection could maintain such traits. The currently observed smaller families of the more intelligent is a too recent effect to explain the survival of genes for low intelligence. The recently reported mitochondrial DNA allele (15,925 bp in the region coding for threonine tRNA) adversely affecting intelligence in Whites (but absent in Blacks) may be an example of an intelligence-raising gene with adverse effects through decreased maximal oxygen consumption. An alternative location (13,365 bp, affecting energy metabolism) for the intelligence affecting mutation is proposed. The apparent slower ageing in the better educated and the more intelligent may be due to less free radical oxidative damage. However, intelligence is a unique trait in that it requires an observer who is himself intelligent to be observed. Thus, at the time in human evolutionary history when the concept of intelligence is first developed by the most intelligent, it is to be expected that alleles for low intelligence will still be being eliminated.
