Evidence for the s count macrogene

Background: A macrogene is defined here as a gene on which successive mutations incrementing a repeat count produces successive punctuated evolutionary events in species that are homogeneous for it. The set of repeat count on the asp (abnormal spindle) family of gene is thought to affect brain size in mammals. Corticogenesis requires two integer valued (quantum) variables, the f and s counts, to determine the number of division cycles during the first and second phases, respectively, of neuron production in the cerebral cortex. Quantum ‘extra’ neuron theory hypothesizes that increments in a quantum variable, the n count, cause punctuated encephalization events in species that are homogenous for it. There is evidence in six pairs of inbred mice strains for one or more major genes affecting brain size. Results: The s count is probably equal to the n count plus a positive integer. The calculated n counts are different in three of the four pairs of strains studied where encephalization data has been previously published. Five different n counts have been found in eleven mouse strains. The difference between the n counts of humans and mice is about 25. Conclusions: Encephalization in mammals may be caused by a macrogene that determines the s count. This theory can be tested by determining the s counts of the various mice strains. However, the asp family of gene is probably not the s count macrogene because the difference in the asp counts of humans and mice of 13 (= 74 – 61) is much smaller than the difference in their s counts of around 25.