Carl Sagan got a lot wrong about the human brain. Carl Sagan popularized this concept in his 1978 book The Dragons of Eden. Learn More
Carl Sagan got a lot wrong about the human brain
Carl Sagan got a lot wrong about the human brain. Carl Sagan popularized this concept in his 1978 book The Dragons of Eden
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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.
When Sagan authored The Dragons of Eden, the triune brain theory was firmly outside the mainstream of scientific thought, as Pitt pointed out in his critique.
Sagan has come up with a really strange theory about the reptilian origins of the human brain, and he has built the remainder of his discussion around it without mentioning the theory's current standing. To give the ideas some credibility, he cites just enough experts in the field, but he doesn't discuss any potential drawbacks, offer any alternatives, or discuss how widely accepted the theory is among physiologists, psychologists, or anthropologists.
Carl Sagan was and continues to be regarded as a trustworthy and cynical broker of scientific knowledge. It's a little surprise that he presented such a contentious hypothesis to the general public as if it were fact. Furthermore, three years later, in his far more widely read book Cosmos, Carl Sagan persisted in promoting the hypothesis. He stated:
Every one of us has a brain that resembles a crocodile deep inside our skulls. The limbic system, or mammalian brain, which arose in predecessors who were mammals but not yet primates, surrounds the R-complex. It is a significant contributor to our attitudes, feelings, and care for the young. Finally, the cerebral cortex is located on the exterior and coexists uncomfortably with the more primitive brains below; civilization is a result of the cerebral cortex.
Reptile brain debunked
Since Sagan informed his gullible readers that they possess reptilian brains, the theory has been thoroughly debunked. The activities of the brain are not divided as MacLean hypothesized, according to brain scans. Additionally, the concept has a fundamental misunderstanding of evolutionary biology. As species diverged from their common ancestors, "complex nervous systems and sophisticated cognitive abilities evolved independently many times," scientists claimed in a review study dispelling the reptile brain myth in 2020.
Another blow was delivered by a study that was printed in the year 2022 issue of the journal Science. To determine whether identical neurons in both species were localized in particular regions of the brain, researchers analyzed the brains of mice and lizards. They discovered that these neurons were dispersed throughout the body, refuting the triune idea. The mammalian brain lacked a distinct "reptilian" area.
Unfortunately, not many textbooks have yet included all of this information. 20 beginning psychology textbooks were chosen at random by the authors of the aforementioned 2020 review, and they discovered that 86% of them contained at least one error that suggested our brains are layered, as MacLean postulated.
Carl Sagan may very well be to blame for that. The idea that humans have a reptilian consciousness hidden deep within the folds of our brains probably would have remained restricted to academia and eventually been dismissed with little fanfare when scientific evidence reduced it to wrongness if it weren't for his nuance-lacking popularizing. Instead, the persistent and pervasive myth of MacLean's triune brain theory endures.
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Guys, I'm David Daniel. I'm joining the Health Frantic team & my primary goal is to bring you exclusive coverage of the world of Health & Fitness.
David Daniel has over 10 years of experience in health and Fitness. She's always exploring — optimizing health through proper nutrition, physical and mental wellness, regular exercise, sweat-proof workout gear, running and self-care practices, and more —