This background information to Chapter 1 is in two, brief, interrelated sections. First, the general steps from pre-human to human, and second, the specific steps in the origin and development of our human brain.
Section 1: Seven to five million years ago in eastern Africa a single biological mutation occurred in our first human ancestor. Most mutations do not survive, but this one did, or we would not be here today... something resembling us perhaps, but not us. The bones we have found show that this first successful mutation occurred in a type of animal we call an ape. That mutation was passed on and began the branch of our family tree which we call hominids, which means bi-pedal (upright walking) apes. Subsequent mutations that bestowed advantage were preserved and these changes eventually led to us, i.e. modern Homo sapiens. All of these genetic changes occurred in one place: eastern Africa.
After our first human ancestor there came several more types of evolving hominid types, including the famous “Lucy,” until about 1.8 million years ago Homo erectus (erect persons) appeared. They had so many human qualities that today they can be considered to have been the first humans, and they were the people referred to in the previous chapter as having defeated the leopard.
Their landscape (the Great Rift Valley of east Africa) was a tropical mixture of woodlands and vast grasslands, called savannas, with occasional mountain ranges. These people were taller than their predecessors, as tall as 5' 6", and had a bigger brain, 900 to 1100 cubic centimeters, smaller than our average modern brain of 1350 c.c. Still, they were able to fashion wooden spears and to chip stone into beautiful hand axes. At some point they hunted large animals, which requires efficient weapons and elaborate social cooperation, although they probably had only the most rudimentary speech; perhaps 20 percent of their calories came from meat. They established home bases, and cared for dependent infants. They probably made the critical transition from the male and female hierarchies of chimp society to the espousal bonds of modern men and women. Erect people overcame their instinctive fear of fire and learned how to control its use.
For whatever reason, perhaps seeking food, some groups of the Homo erectus people began to move northward in Africa. This occurred about 1.2 million to 700,000 years ago, during a warm, wet period when the Sahara Desert had enough rainfall for groups to cross it safely. Eventually their descendants crossed the land bridge from Africa to Asia and moved into the Near East, Europe, parts of northern Asia, and tropical southern and southeastern Asia. They could not inhabit extremely cold places, such as most of northern Eurasia, and they did not reach Australia or the Americas.
The descendants of these early Homo erectus persons can be grouped by three different locales: Europe, including the Mediterranean region; eastern Asia; and eastern Africa.
1) The Homo erectus people who went north into Europe and mutated to become Neanderthals are in the fossil record from about 130,000 to 28,000 years ago. Thus they originated before the start of the last ice age, about 90,000 years ago, and were the first persons to adapt successfully to life on the edge of an ice age world. More bones of Neanderthals have been found than of any other hominid group, including some thirty nearly complete skeletons. (They are named for the Neander Valley skeleton found near Dusseldorf, Germany in 1856.) They had a bulky, squat physique with heavy muscles and barrel chests in men, women, and children, to offset the cold. .
As tool makers, Neanderthals did not change their designs over tens of thousands of years. From stone they made borers, scrapers, points, knives, and hand axes. The position of their larynx suggests that they could not make as many sounds as modern humans, but the extent of vocal language is not known. Examples of their DNA taken from bones from 30,000 years ago show that they could not have been our ancestors. Neanderthals are now seen as a specialized form of Homo erectus who became physically adapted to extreme cold. They wrapped fur hides around themselves for warmth, but did not sew them together to make clothing. However recent finds of hole-boring awls suggest that they fastened fur hides together for warmth. Eventually they were replaced by Homo sapiens.
2) The Homo erectus people who went to eastern Asia were the first hominids to arrive, and there they developed distinctive adaptions to the forest environments of tropical and temperate Asia. Forests rather than grasslands meant that people had to keep moving in order to find fruits and nuts. Lacking stones to make tools, they used bamboo and wood, raw materials that are not preserved in ancient sites. These Homo erectus forest cultures flourished and evolved slowly over hundreds of thousands of years independently of changes in humankind in Africa and Europe. Homo erectus persons seem to have lasted several thousand years longer in Asia than in Europe and Africa, but eventually were replaced by Homo sapiens.
3) The Homo erectus people who remained in Africa, and over time mutated to become us, i.e. Home sapiens. Using their superior brains and language abilities they gradually replaced the remaining groups of hominids in Africa and reached a population of perhaps 50,000 by around 100,000 years ago.
Section 2: To understand our Story from this point on we need to begin to consider, very briefly, some vital facts about our human brain. (We will continue this subject in later chapters.)
The place to start is to recall J. Huxley’s model of the Universe as being a single, on-going Process of Change (Evolution), occurring in three main phases : non-living (or inorganic); living, (or organic); and human (or psychosocial). The first phase began with the “Big Bang,” which created space, in which were formed the atoms which combined to form galaxies of stars, planets, etc; the second phase came out of the first phase with the emergence of the building blocks of life (at least on Earth); the third phase came out of the second phase with the emergence of human beings (at least on Earth). All three phases of change continue to occur today, and comprise what we call the evolution of our Universe, or in one word, Evolution.
To find the origin of our brain we must turn to the second (living) phase of the Universe, with the emergence of small sea-animals, such as jellyfish, which had a pre-brain composed of a group of neurons (brain cells) called ganglia. Then there emerged fishes with spines (backbones), and through these spines neurons gradually were guided to the head and began to form a true brain acting as a central nervous system. It continued to evolve in a series of vertebrate (backboned) land-adapting animals and eventually became the reptilian brain. (Early neuroscientists described our brain as being comprised of two parts, an old brain and a new brain.)
Next we must turn to the work of the eminent neuroscientist Dr. Paul MacLean (1913 to 2007), who for 14 years was chief of the Department of Brain Evolution and Behavior at the U.S. National Institutes of Health (NIH), one of the great research centers of our time; his brilliant work spanned 6 decades.
The background is that during his research MacLean noticed a striking similarity between the three brains in our head and the brain structures in the heads of the three major animal groups of evolution: reptilian, old mammalian, and new mammalian. He and his team traced these parallels and found that each of our three human brains matches a brain developed during each of these three evolutionary epochs.
The picture which emerges is that in Nature a system that works is never abandoned; instead of that, new, enlarged, and more efficient systems are built upon the old, forming a new composite system. During the evolution of our brain, on top of the reptilian brain a “cortex”(from the Latin word for bark) began to form, and eventually covered it and became the “old mammalian” brain. Then on top of it a new cortex formed and became the “new mammalian” brain (neocortex). The role of each new brain was to correct problems in an older brain and/or to expand its possibilities. Each new brain is “smarter” than its predecessor, but must accommodate its vital workings.
MacLean called the combination of reptilian, old mammalian, and new mammalian brains the Triune Brain, and found that it operates like three interconnected biological computers, each with its own special intelligence, its own subjectivity, its own sense of time and space, and its own memory. When integrated, these three systems offer us an open-ended potential, an ability to rise and go beyond all constraint or limitation. But when integration fails, our mind is a house divided against itself, and we can become our own worst enemy. Following are very brief descriptions of the three brains (which today form the basis of the composite human brain):
The Reptilian Brain, (called by MacLean the R-system). This “first” brain is the oldest and most primitive “mentally”of the three, and yet was an enormous advance over the fish brain. Originally called by neuroscientists the “hind brain,” it is our sensory-motor system, i.e. the spinal cord, the body’s vast network of nerve endings and their neural connections, and the primary neural systems in the heart. Its basic function is to keep the body alive and well. This first brain is a central nervous system which controls muscles, balance, and autonomic functions, such as breathing, heartbeat, and digestion. It functions in a habitual, patterned way and is unable to alter either inherited or learned behavior.
Its responses to stimuli are simple, like those of a reptile’s brain today. When a reptile’s primitive vision spots a moving clump of contrasting light and dark (the only visual discernment it can make), the reptile asks, “Is it something to eat, mate with, or be eaten by?.” Thus its choice is to to go for it, or get away from it. The energy and motivations of the Reptilian brain, or “R- system,” are still the basic “us,” and our newer, higher brains build on its workings toward creating the increasingly more complex abilities which make us “human.”
The Old Mammalian Brain covers the Reptilian brain and this “second” brain too is concerned with emotions: feeding, fighting fleeing, and sexual behavior. As MacLean observed, everything in this emotional system is either “agreeable or disagreeable: survival depends on avoidance of pain and repetition of pleasure.” It screens and prioritizes incoming sensory messages on their way to the Reptilian brain. (In 1952 MacLean coined the name “limbic system” for this middle part of the brain, from the Latin word “limbus,” meaning “to border.”)
This second neural system is called also the emotional-cognitive brain, for here Nature adds to the reptile’s limited senses our extraordinary senses of smell and hearing which lift the entire
sensory system to a new order of functioning and open an entirely new world. Additionally in this nurturing emotional brain are the foundations for all forms of relationships, including our general cognition of the world as somehow “other,” as something to which we must relate. As noted, a reptile’s relationships are simple; the new mammalian system is infinitely more complex, and infinitely more discriminating. The collective term for these tools by which we qualitatively evaluate all our relationships, particularly with each other, is emotion.
The New Mammalian Brain (Neocortex or verbal intellectual brain) covers the two earlier brains, and is divided into left and right hemispheres joined together by the corpus callosum, a thick band of nerve fibers. The left half controls the right side of the body and the right half controls the left side of the body; the right side is more spatial, abstract, musical, and artistic, while the left side is more linear, rational and verbal.
This high, “third” brain introduces language and thinking, the ability to stand outside all other activities of the brain and observe these activities objectively and consider all factors of a situation rather than react to them from instinct alone. It occupies five times more skull space than the reptilian brain and the and the old mammalian brain combined, covers them, and consists of some hundred billion neurons, each of which is capable of interacting with upward of a hundred thousand other neurons to form fields of coordinated neural action. These enormous neural fields translate particular frequencies to our awareness, and our awareness to other fields, all of which field effects are constantly shifting and changing, updating their various intelligences and reports.
There are no limits to what our third brain can translate, from input from the world outside to imagination and thought within. With the development of this third brain Nature opened an infinitely wide window of awareness. This intellectual-creative brain introduces creative imagination, which is the foundation of all organized thought and creative intelligence. Whether we open ourselves to adventure or close ourselves in a defensive posture, refusing to engage, depends largely on the experiences we have in the first three years of life. These years mark the time when our emotional system develops the foundation for our higher intellect yet to come.
The first brain registers present tense only. The second brain computes both present and past. The third brain adds awareness of the past, present, and future, and this new dimension broadened our window of awareness greatly.
The prefrontal cortex or prefrontal lobes. Next, MacLean recognized and studied the "fourth" brain in our head, located immediately behind the ridge of our brow, in front of and attached to our neocortex.
While our reptilian brain has molecules or parts that are hundreds of millions of years old, indications are that only about 40,000 years have passed since our prefrontal lobes appeared and began to develop toward their current size and significance. MacLean attributed to them "our higher human virtues" of love, compassion, empathy, and understanding, plus our advanced intellectual skills. This fourth, newest, and largest system should be guiding the Triune brain, but for reasons which we shall come to later, the creation of the ideas which would have caused that has been surpressed.
There is a "fifth," very important brain, located in our heart, which we will consider later.
(To continue our Story, click below on HOME. Then go to Blog Navigator and click on Part Two: Chapter 3 - Elements)
