Suzana Herculano-Houzel - TED Talks "What is so special about the human brain?" Video
"All brains are made the same way"
Neuron counts grow linier with brain size
Debunked because the same-weighted brain in different animals (cows vs chimps), they have different cognitive capabilities.
The largest brain should have the most complex cognitive capabilities
Elephant brain weighs 4-5kg, human only 1.2-1.5kg, whale up to 9kg, but we perform better cognitive function than them. What caused this?
Extra cortex? Gyrification to expand the surface of our brain? Since we do not grow the space of our skull, so the gyrification is the answer?
Our brain counts only 2% of body mass, yet consume 25% of body energy.
Human brain: larger than it should be, uses much more energy than it should, so it's special?
"Brain soup" dissolves brain in detergent but keep the nuclei intact.
To count the number of neurons in our brain. Turns out, our brains are not made in the same way.
In rodents, as the size grew large, 10x more neurons, 4x larger: brain 40x larger. In short, it gains size more faster than it gains neurons.
In primates, 10x more neurons, same size: brain 10x larger. So the same size of primate and rodent would carry different number of neurons.
Human have 16 billion neurons in the cortex, 86 billion neurons total neuron in our brain.
Our brains are remarkable, yes, but it is just a large primate brain.
"Why does it cost so much energy then?"
1 billion neurons cost 6 kcal/day, through simple linear function it is just exactly right, our brain cost around 500 kcal/day.
"How did we have so much neurons?"
Why did the bigger-brain owners does not have more neurons?
They can't afford the energy from raw foods.
Neurons are expensive. To get more neurons, they have to give up body weight to compensate the energy expenses of the brain. The tradeoff is 8 hours of eating/day to afford these neurons.
With 86 billion neurons, we should spend 9 hours/day feeding raw foods. If we ate like a primate, we should not be here.
Which is why our ancestors invented.. cooking.
To cook is to pre-digest our raw foods, makes them softer and yield much more energy in much less time.
Cooking frees our time to do much more interesting things with our day.
Conclusion
Our brains are not special.
We have the largest number of neurons in the cerebral cortex.
We can afford it because we cook.