Why Are Our Brains Shrinking?

[aphar]

Summary:

1. Hominid brains were getting bigger, but around 70kyo they plateaued, and have been shrinking ever since. Over the last 20k years, human brains have shrunk from 1,500 cubic centimeters (cc) to 1,350 cc.


2. The encephalization quotient, EQ, is the proportion of brain size to body size.
   (The more muscles one has, the more brain one needs to control them).
   Human 7.4, dolphin 5.6, whales 2.9.
   Brain shrinkage moving much faster than our body shrinkage.


3. Human brain uses around 25% of the energy but accounts for only 2-3% of body weight


4. Synaptic pruning is the process of synapse elimination that occurs from the time one is born until mid 20’s.


5. Idiocracy: As population density increases, humans don’t have to be as smart to stay alive because they can rely on other people to support and protect them.


6. Dysgenic pressure: education and birth rate are inversely related


7. Domestication: domesticated animals have a brain 10-15% smaller than its wild ancestors.