Natural selection traded costly muscle for fat to store energy for big brains
Evidence
To understand this, realize that big brains are energy hogs. Our brains use between a fifth and a quarter of the energy we take in each day, while the brains of other primates use between 8% and 10%. Other mammals use only 3% to 5%. Even worse, unlike muscles, you can’t shut down a brain to save energy; it takes almost as much energy to sustain a resting brain as it does an active one. … The emergence of tools and weapons allowed natural selection to trade expensive tissues for fat, which is cheaper to maintain and provides an energy-storage system crucial for sustaining big brains through periods of scarcity. … This is why infants, who devote 85% of their energy to brain building, are so fat—they need the energy buffer to sustain neurological development and optimize cultural learning. — Joseph Henrich, The Secret of Our Success, 236
Categorization
- XREF: Energy-budget logic used to explain infant fatness and weak adult bodies; links to fat-storage evolutionary arguments common in paleoanthropology. — connects to: Culture-driven cooking let natural selection shrink gut tissue to fund bigger brains — Joseph Henrich, The Secret of Our Success: How Culture…, 233; Bigger-brained species evolve longer childhoods to permit learning — Joseph Henrich, The Secret of Our Success: How Culture…, 957; Natural selection stabilizes at local optima, as armor-plate shifts in sticklebacks show — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 180 (+1 more)
Broader Connections
- Brain expansion via longer lifespans makes species extinction-prone
#complicates(0.75) — Joseph Henrich, The Secret of Our Success, 977 - Bigger-brained species evolve longer childhoods to permit learning
#corroborates(0.72) — Joseph Henrich, The Secret of Our Success, 957 - Natural selection stabilizes at local optima, as armor-plate shifts in sticklebacks show
#complicates(0.72) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 180