Free Energy Rate Density of the Human Brain

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Brendan Graham Dempsey:

"Humans, who exceeded in this drive towards mentalization, became the most complex of all. Estimating the free energy rate density of the human brain—his preferred metric for complexity—Eric Chaisson writes:

In turn on up the complexity continuum, the adult human brain—the most exquisite clump of matter in the known universe—has a cranial capacity of typically 1300 g and requires about 400 kcal per day (or 20 watts) to function properly. Our brains therefore have a Øm value of roughly 1.5 × 105 erg s-1g-1. This large energy density flowing through our heads, mostly to maintain the electrical actions of countless neurons, testifies to the disproportionate amount of worth Nature has invested in brains; occupying 2 percent of our body’s mass yet using nearly 20 percent of its energy intake…

To put this in perspective, according to the same metric, the free energy rate density for galaxies is 0.5; for stars, 2; for planets, 75; for animals, 20,000, and for human brains: 150,000! This makes human brains one of the most complex, energy-dense things in the known universe."