“By sacrificing intelligence, diving mammals become endowed with a greater capacity to withstand oxygen depletion, an attribute which presumably has important survival value. Thus, relative stupidity may be more important for species survival under some conditions than relative intelligence.1”
“In one sense the turtle has traded off intelligence for an amazing ability to withstand profound O2 depletion. Whatever the ultimate wisdom of this choice from an evolutionary standpoint, it may be pointed out that the turtle has survived (on an instinctive and reflex basis) largely unchanged as a stupid animal for over 200,000,000 years . These studies indicate that the possession of a very small brain which does not function vigorously may have important survival value.”
“It is of some interest that this same analysis may be applied to mammalian species during fetal development. It is well known that the brains of immature mammals are better able to withstand anoxia and ischemia than those of more mature animals …increased metabolic demand associated with increasing functional and structural brain complexity is found postnatally and is paralleled by a decreasing resistance to anoxia . In any case the fetal brain, like turtle brain, is relatively stupid but capable of withstanding extreme O2 depletion.”
“The brain which designed spaceships has also designed the hydrogen bomb. The brain which created the Eroica created the crematories of Auschwitz….The development of a brain in which intelligence is not invariably coupled to constructive purposes could easily prove to be a lethal evolutionary trait.”
It might be more useful to be ‘stupid’ rather than ‘intelligent.’
“Modern molecular biology suggests that the structure and function of the brain depends on mechanisms which are common to all cells. Thus, sensory experience , memory , and learning  involve the biosynthesis of new protein, macromolecular metabolism, the RNA and DNA systems, energy metabolism, and ion transport.2 It is fascinating that brain RNA and brain protein increase during learning in a manner quite similar to increases in these components in skeletal muscle during prolonged physical exercise .”
“In the context of this essay two conclusions might be drawn with respect to these findings.
- “The differences in intellectual capacity between various species are quantitative rather than qualitative. The qualitative difference is extensive but does not necessarily constitute an evolutionary discontinuity.
- “Intelligence is a trait which has arisen through the same processes which give rise to other biological properties. As such, it is subject to the same evolutionary pressures as other biological properties and may play the same evolutionary role as that played by other biological properties.”
“Whatever the merits of the present analysis, perhaps it will prove useful to question whether man is really the most superior species, whether intelligence is really a property with great importance for the survival of the species, whether evolution always proceeds in an upward direction, and whether man as a species is immortal.”
“It could be argued that the major virtue of intelligence is to provide the possibilities of additional degrees of freedom of choice which are not available to other species. How these degrees of freedom will be used is not clear. If through an atomic holocaust man as a species disappears and the turtle (of all the vertebrates) inherits the earth, then truly it will be an evolutionary victory of stupidity over intelligence!”
NCBI: The Evolutionary Advantages of Being Stupid (1973)