Carl Sagan got a lot wrong about the human brain

Introduction:

Carl Sagan, an astrophysicist and science communicator, was and continues to be regarded as a trustworthy and skeptical broker of scientific knowledge. However, Sagan supported a contentious theory of human brain evolution in his Pulitzer Prize–winning book The Dragons of Eden, claiming that humans have a “reptilian” brain buried deep within our thoughts. The notion has since been thoroughly debunked, but Sagan’s faulty popularization is very certainly to blame for the fallacy that humans have a reptilian brain.

Astrophysicist and gifted science communicator Carl Sagan only ever received the prestigious Pulitzer Prize for nonfiction writing, and it wasn’t for any of his timeless works like The Demon-Haunted World, Pale Blue Dot, or Cosmos. Sagan instead took up the award for his rather less well-known book The Dragons of Eden, in which the physicist ventured into the realm of intelligent design theory.

When Dragons was published in 1977, critics from traditional media outlets praised it as a “delight” that would enchant readers. However, several reviewers with backgrounds in science were noticeably less complimentary.

Professor of Philosophy of Science at Virginia Tech Joseph Pitt praised the book in the journal Human Ecology, calling it “crammed full of fascinating bits of information, intriguing theories, humor, vision, and some caustic observations about society as a whole.” It lacks rigor and intellectual balance, however. Pitt was particularly offended by Sagan’s promotion of a little-known, far-fetched idea by Yale University physiologist and psychiatrist Paul D. MacLean, who took up much of the book.

Triune brain theory

According to MacLean’s triune brain theory, the human brain developed in layers. human ancient reptilian relatives gave rise to the deepest region of the human brain, which is in charge of movements and breathing as well as instincts like hunger, survival, and mating.

The limbic system, which is located in the second layer and regulates emotional reactions, evolved in more recent mammalian ancestors. The cerebral cortex, the third and last layer, is only present in humans and is responsible for language and reasoning.

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