A New Part of the Brain

As hominids appear, how is the brain doing? That remarkable set of evolutionary events (warm-blooded, lactation, live birth) caused an ever-larger brain structure. A new part of the brain developed. Housed here are the concepts of satisfying and not satisfying behaviors as well as a variety of other emotional behaviors. For example, solid research has established that our first look at a stranger leads to a like-or-dislike decision. The thoughtful brain may later change that opinion; but the instinctive brain sets the stage. Humans make a lot of their decisions based on that quick, unconscious reaction. The quick reaction appears first in the evolutionary line; the thought response is much later — and slower.

From this new part of the brain, rarely does a signal cause a behavior to happen. Instead, it produces tendencies to respond in certain ways. The brain did NOT develop with higher brain functions separated from automatic reflexes. For example, if a person partakes in some sexual activity that is clearly career-ruining, people ask, “What was he thinking!” to which the answer is, “He was not thinking.” His response was an uncontrolled, automatic emotional response. This part of the brain contains the value judgments humans often unconsciously make. These responses made unconsciously exert a very strong influence on our behavior.

Social interactions required more brain space. Eventually, as language, imagination, beauty and abstract thought appeared, the brain needed to grow bigger by adding layers. These demanded an addition to the brain; in fact, two additions to the reptilian brain, one to the backside of the brain and the other to front part. At home here are language, abstract thinking, imagination and awareness of ourselves. In most mammals, they add just a little; in humans, they sort of cover up the original reptilian brain.

In the past few years, those studying the brain have taken issue with past beliefs that the brain was, in a sense, compartmentalized, left brain for some things, the right brain for others, sort of like LEGO blocks. Those left-brain this, right-brain that ideas have been dismissed. The two sides of the brain share a common basic structure.

Brain sections dealing with higher order thinking evolved side-by-side with the earliest layers. Communication pathways within the brain, when faced with a new issue, somehow seek out all the various areas of the brain related in some manner to that new issue. You see the word “taco.” The brain reaches for all possible connections. Neurons will zip off, searching for possible prior experiences with “taco” that are stored in your brain. Since each person has unique environmental experiences, the neuron firing will differ from person to person. One big integrated systems responds immediately to some query reaching the brain.

For a newborn, the brain’s visual circuitry only connects as needed by the newborn’s eye. If an infection distorts so seriously that infant’s eye to make it functionally blind, correction by surgery done ten years later cannot rebuild the pathways that should have been built much earlier. Those millions of potential connections available earlier, the ones that need to be activated by use, seem to have an alarm clock. After a while the alarm clock goes off; thereafter, the connections disappear, never again to be made. The number of available connections is largest at age 2; by adulthood, only about 60% of available links have been connected. The other 40% were pruned; gone.

Thus the brain of a child born in a home where only English is spoken connects some different nerves then that of a child born where only Chinese is spoken. The connections for those two will differ from a child born where only Finnish is spoken. A child born where all three are spoken will make all the connections. In a sense, then, cells that fire together wire together. Timing is critical; available nerves which are not connected within a certain time period eventually disappear. The timing of the action-potential activity is critical in determining which connections are strengthened and which are weakened and eliminated.

For a child, good vision requires being exposed to a sharply focused visual world during this period of brain development. Without that, the child will not have normal brain development. Your author is a living example. Born with severe astigmatism — so severe the first ophthalmologist labeled it “functional blindness” – the default was not identified and corrected until age 8. Strong eye-glasses then solved the problem. But that was too late. To this day, concepts are easy (Darwinian evolution, probabilistic statistics, the entire number system) but details (remembering the spelling of words, recalling what the person who just left had been wearing, remembering a name one minute after an introduction) are all impossible. No part of my brain has a place for those. If the connections for seeing the details were never activated; before age 8, they disappeared.

This does not mean all learning ends as adulthood looms. The brains of mammals continue to respond to and learn from new experiences. The newer parts of the brain – the ones that developed after reptiles appeared – can make new connections. Brain researchers have a number of interesting theories on how that exactly works but the bottom line is: learning continues essentially until death.

The hominid level is reached. The brain and emotions have come a long way. Animals by this time had displayed a wide variety of emotional behaviors which the brain caries from one evolutionary step to another. At the fish level was seen fear, learning, memory, parenting, caring for others, and seeking one another. Earlier, cooperation, communication and what appears to be a mysterious force of attraction.

In the long transition from amphibians to reptiles, parenting appeared to have a role. Now review the role of parenting in these steps to lactation, warm blooded, placenta developed, live birth started, and the newborn needed parental help to stay alive. Elaborate mating rituals involve color, sound, body movement. Mating and sex go together; research indicates animals enjoyed sex. Darwin: “Males drive away rival males .. females excite or charm those of the opposite sex and select the most agreeable partner.” Social harmonies appeared. Some mammals stay with a mate for life, confirming once again gender attraction seen since genders appeared. Research shows the roots of empathy are embedded deeply in our evolved behaviors. Sharing and cooperation become broader. Death was understood.

A Review of Brain Development

Reaching back almost to the beginning, our brain uses a communication system found in jellyfish, first appearing 600 million years ago. Their nerves and the manner they send signals are similar to ours. Your brain relies heavily on structures found in the animals that preceded us. The first known animal, sponges, appear just before jellyfish. They basically had a more primitive form of the communication system found in jellyfish BUT our brain still uses part of their communication system. How that process evolved between the first multicellular organism and sponges is unknown since fossils are not available.

Worms are the simplest organisms to have a central nervous system, allowing them to exhibit more complex forms of behavior. Insects have a small but remarkable brain which can, for example, permit the cockroach to dart away as soon as it senses the moving air preceding a quickly descending human foot. The insect brain controls crawling, hopping, swimming, flying, burrowing, mating, and you-name-it.

An animal’s information system runs up the spine to the brain. Vertebrates, with that stiff spine, improve the protection of the information system. In early vertebrates, one part of the brain controlled behaviors that had happened again and again. Those automatic responses are sort of like cruise control on a car. A bird flies straight at your head. You do not stop and ponder, “Hmm. Should I duck?” No. Your conscious brain is too slow; a reflex established in antiquity makes you duck.

Science quarrels when the first brain appears, but the more important question is “What does the brain do?” Basically, it signals; it communicates; it directs traffic.

Without using the term “brain,” signaling began with life. From the beginning, cells had a communication system. Without one, how else could the DNA of the first bacteria direct the organism to make a copy of itself and then reproduce by splitting that copy off? Each of those steps, from no-life to life, from bacteria to eukaryotes, eukaryotes to multicellular, multicellular to jellyfish, required cells signaling one another. For sure, the brain was more organized when vertebrates had it at the end of a central nervous system. But communication among cells had to begin with life itself.

The amphibian transition from water to land made a big impact on the brain’s development. By this time, the brain had a midbrain and forebrain where brain functions for hearing and seeing in a higher and drier world sharpened. One part of the brain included responses like dominance and submission. Sudden movements, intimidating objects and brighter light changed visions centers. A possibly threatening or sight or sound causes us to instinctively turn our face and eyes in that direction.

As the finished reptile appears, the brain controls vital functions like heart rate, temperature, breathing, and balance. The brain, at that point, has a brain stem connected to two spheres (called the cerebellum.) This section helps with learning new motor behaviors, such as swinging a golf club.

In addition, most of science agrees that emotional centers also existed in the reptilian brain. Likely members include the instinct to fight or run which might also be called terror or anger. Instincts regarding sexual drives as well as parenting can be found here.

Dinosaurs, birds and mammals all followed reptiles. Each of those began with the same brain structure – the same brain structure as the reptiles. The human brain contains that section (often called reptilian) which still controls involuntary and instinctive behavior. Contrary to the arrogant beliefs of too many humans, the brain did not start over when homo sapiens arrived.