History of Human Ecology Theorization
7,000 years ago, surgeons bore holes in patients’ skulls to cure afflictions. The exact purpose – whether to treat chronic headaches or mental illness or provide an easy escape route for evil spirits – remains a mystery. Some patients underwent multiple operations.
5,000 years ago, ancient Egyptians wrote about different symptoms of brain damage. But the heart was considered the seat of the soul, the keeper of memories.
Egyptian practice – for those wealthy enough – was to carefully preserve a body for the afterlife. Part of this process involved scooping the brain out through the nostrils and discarding it; no need for this skull stuffing any longer.
2,500 years ago, observant Greeks correlated structure to function. Body parts differ to perform different functions: the feet for walking, the hands for grasping, the head, with eyes, ears and mouth, specialized for sensing the environment. Dissection showed nerve tissue pathways to the brain, which must be the organ of sensation. Greek physician Hippocrates (460–379 bce), father of Western medicine, opined that the brain was not only a sensation organ, but also the seat of intelligence.
Aristotle (384–322 bce) clung to the notion that the heart was home to the intellect, while the brain acted as a radiator, to cool overheated blood. Aristotle thought that human capacity for rationality could be explained by the large cooling capacity offered by a big brain.
“Each man is the architect of his own fate.” ~ Galen
A few centuries after Aristotle, the Greek physician Galen (130–200) drew upon his extensive experience with animal disections, as well as his practice as gladiator physician, where he had the benefit of dealing with mangled combatants, including, no doubt, severe head and nerve injuries.
Galen corroborated Hippocrates: that the brain was the center of mental processing. Using the time-honored presumption that function follows form, Galen tried to deduce the respective processing of the cerebellum and the cerebrum.
Poking about revealed the cerebellum sinewy hard and the cerebrum a bit mushy. This led Galen to the conclusion that the cerebellum commanded the muscles, while the cerebrum was the recipient of sensations, which it stored.
To form memories, sensations must be imprinted. A doughy cerebrum fit.
Galen was not far off. The evolutionarily early cerebellum acts as a movement control center. The cerebrum is largely concerned with perception of sensations and memory.
Galen went further in his explorations, to mechanics. The prevailing theory at the time was that the body functioned according to a balance of 4 humors (vital fluids).
Galen’s dissections revealed the brain as floating in fluid, and having hollow sections, ventricles, like the heart, where blood is pumped throughout the body. So, Galen reasoned, sensations were registered, and movement initiated, by movement of humors to and from the brain through the nerves. Nerves were believed to be hollow tubes, like blood vessels.
Galen’s take on the brain prevailed for nearly 1,500 years. The concept of ventricular localization of brain function went unchallenged.
Galileo (1564–1642) proposed that the planets acted as inanimate bodies, moving mechanically. A contemporary, William Harvey (1578–1657), studied anatomy in Padua, Italy, where Galileo lectured. Harvey chronicled blood circulation through the body, with the heart functioning like a pump. Hydraulic mechanical pumps had already been developed in the early 17th century.
The scientific bent swayed to that of a mechanist world, with organic life subject to the mechanical laws of motion. The 2,000-year-old Greek view that all of Nature was a vast living organism was overthrown by this ‘advanced’ concept.
The brain, like the heart, was a pumping machine. And, just like machines, the body could not itself replace parts that were damaged.
“The two operations of our understanding, intuition and deduction, on which alone we must rely in the acquisition of knowledge.” ~ René Descartes
French philosopher and mathematician René Descartes (1596–1650) advocated the fluid-mechanical theory of brain functioning: that the brain acted as a pump, albeit with a Christian twist.
The brain-pump theory could explain animal behavior, but Descartes considered it inconceivable that cranial fluid mechanics could account for the full range of human behavior. Descartes reckoned that people possess intellect and the ability to reason unlike other animals. Beyond that, only humans had a God-given soul. The unique mental and spiritual gifts that made humans above all other animals resided outside the brain, in the mind. Descartes surmised that brain-based functions in humans applied only to those behaviors that resembled that of the beasts.
Touting dualism, Descartes believed the mind was a separate spiritual entity, receiving sensations and commanding brain-directed movement via the pineal gland, which was the “seat of the soul.” The pineal gland is now known to regulate biorhythmic functions, such as the circadian rhythm (wake/sleep cycle), by production of the hormone melatonin. Production of melatonin in the pineal gland is inhibited by being in sunlight and stimulated by darkness.