By comparing the amount of information estimated to be in the genes of different types of animal with the amount of information estimated to be in their brains, Carl Sagan deduces that somewhere in the steamy jungles of the Carboniferous Period animals emerged with more information in their brains than in their genes. This estimate is quite imperfect because the information is imprecise and the figures cover a large range requiring logarithmic relationships which exaggerate errors. But, though the date of the crossover is inexact, the notion seems valid. Since the crossover point, whenever it was, brains have increasingly dominated genes. Some dinosaurs, having passed the threshold, might have built up an evolutionary head of steam for intelligence.
Evolution is faster for birds and mammals than for the cold blooded amphibians, fish and reptiles.
At the annual meeting of the British Association for the Advancement of Science in 1988 Allan Wilson, of the University of California at Berkeley, proposed that animals with larger EQs evolve faster than less brainy relatives. Wilson believes the increase in brain size accounts for their difference in evolutionary speeds. If true then one can expect an explosive evolution of the brain by positive feedback. To measure evolutionary differences, Wilson took 20,000 bone measurements from 400 species of vertebrates. From these results he created an index of how different the shape of the body was for any two vertebrate species.