Energy frugal brain
From BurnZero
Energy in the universe is finite. This is arguably on of the most important evolutionary pressures of gene transmission. Genes which coded for structures within the body that expended more energy make the entire organism less efficient and therefore reduces its fitness to propagate. The brain is the third largest organ in the body and is so rich in nerve cells, it is the most energy-demanding organ, using one-half of all the sugar energy in the body.