The Four Phases of Human Evolution

One of the oldest animal species alive on Earth is the horseshoe crab, which originated some 445 million years ago. These odd-looking marine animals evolved into their present form about 250 million years ago and have not changed much since then. They survived through the perils of natural selection when many other species did not.

Now contrast these ancient creatures with our recent human ancestors, the primates which began to climb down from trees and walk upright perhaps as early as 6 million years ago. Our particular species, Homo sapiens, emerged only about 250,000 years ago. Compared to other species of animals on Earth we humans are very young. We are still evolving, and in all probability, are nowhere near the culmination of our evolutionary journey.

The broad view of human evolution can be divided into basically four phases. The first phase for humans as well as for all forms of life on Earth was the great leap from inorganic atoms such as carbon, hydrogen, oxygen, and nitrogen into organic amino acids, which after being churned into myriad compounds in the warm waters of the early Earth, began to group together into strings called polypeptides. Strings of about 20 amino acids became proteins, the complex bio molecules that would evolve to become important in every living creature.

Various theories have been postulated as to how chemical entities combined to make living cells that reproduced and emerged into multicellular creatures. Whether life started in warm pools, around hot ocean vents, or as some people believe, from meteorites that brought the first amino acids to Earth, by about 3.8 billion years ago, carbon-based life as we know it, was at the threshold. 

It then took several more millions of years and layer upon layer of trial-and-error complexity until evolution produced what scientists call LUCA, or the Last Universal Common Ancestor, a primitive hypothetical organism that contained DNA, RNA, and protein and other chemicals and organelles present in living cells today. From LUCA, the three forms of life on Earth, archaea. bacteria, and eukaryote cells branched out.

One of the earliest forms of living creatures was bacteria made of a single prokaryote cell. Neither plant nor animal, bacteria was an important link in the evolution of life and today it is still an essential component of nearly every creature. As writer Bill Bryson points out: “Bacteria got along just fine for billions of years before the evolution of humans, but we could not live one day without them.” Just one example of the work they do is that billions of them live in our gastrointestinal tract and help digest the food we eat.

Although biologically not considered a plant, a type of bacteria called cyanobacteria evolved about 3.5 billion years ago to have enough chlorophyll in it to be able to photosynthesize sunlight and carbon dioxide into oxygen, the element with 8 protons, 8 neutrons, and 8 electrons that gave primitive life the energy to evolve into complicated multi-celled plants and animals. Called one of the most important metabolic innovations in the history of life on Earth, photosynthesis in plants produces the food we eat and the oxygen we breathe. We would not be here without cyanobacteria and photosynthesis.

A second evolutionary leap occurred when primitive prokaryote cells, found in archaea and bacteria evolved into more complex eukaryote cells found in multi-celled plants and animals, including us. One process that is currently accepted is the endosymbiosis theory advocated by biologist Lynn Margulis. Symbiosis occurs when two organisms establish a relationship of mutual interdependence that is beneficial to both parties. For example, flowers and honey bees are said to have a symbiotic relationship. By going from one flower to another getting nectar to make honey, bees pollenate the flowers and help them grow.

Margulis established that some prokaryote cells evolved specialized organelles such as mitochondria and chloroplasts that eventually evolved into the complex eukaryote cells. She called the phenomenon of symbiosis “the source of innovation in evolution.” it is found in just about every phase of evolution from the coming together of cells to form multi-celled organisms such as humans. And we now understand that it is symbiotic cooperation among humans that has enabled us to build our global civilization.

It has been said that the evolution of stars from hydrogen and helium atoms seems less complex than the evolution of life on Earth from atoms to thinking humans. Stars form when hydrogen and helium atoms conglomerate into clumps and the tremendous gravitational pressure on them causes them to fuse together in a process called stellar nucleosynthesis. This process produces the light that plants use in photosynthesis and the warmth we enjoy on a sunny spring day. That extremely hot phenomenon is certainly not easy to duplicate on Earth. Scientists are working diligently to reproduce atomic fusion as a viable energy source to replace the burning of fossil fuels.

But the emergence of living creatures on the other hand, required a chance coming together of inorganic atoms in just the right arrangement and in just the right environment until something wiggled and managed to reproduce itself. That might have been a one-time event. Scientists are not sure. At this time, scientists are still working on the details of how the inorganic to organic transition happened, and if it is possible that if the process has occurred other places in the universe.

As life spread across the globe, every species became subject to natural selection. A species either adapted to its environment or perished. In fact, it has been estimated that up to 99% of all the species that have ever lived on Earth have gone extinct, done in by climate changes, predation, volcanoes, and other phenomena. One of the most profound natural phenomena that affected human evolution was when an asteroid hit Earth some 66 million years ago and wiped out the dinosaurs.   

Mammals at that time were small unimportant creatures that served primarily as food for larger predators. After the demise of their reptilian predators, however, mammals were able to grow and evolve into much larger creatures. A variety of lines branched out, with some dying off and some continuing to evolve until the rise of primates such as chimpanzees, bonobos, and gorillas. Some of these evolved the ability to use rudimentary tools to obtain food. Chimps, for example, figured out how to use sticks to probe into termite hills and catch edible termites.

Then roughly six million years ago some of the primates began walking upright. The reason for this could be an evolutionary adaption due to environmental changes in Africa that caused some of the forests to die out and the land turn into grassy savanna. The tree-dwelling primates were forced to learn to walk on flat land instead of swinging from trees. They quickly learned that walking upright on two legs was advantageous for seeing a greater distance than when walking crouched over on four legs. Also, two legs facilitated running, either toward prey or away from predators.

Over the years, along with the morphological changes that came with learning to walk upright, came other evolutionary changes such as visual acuity, dexterous hands with an opposing thumb, and, most importantly, larger brains. With these physical and mental changes, some primates learned to adapt more easily to their environment and survive when other animals did not.

Then around 2.3 million years ago, another great evolutionary leap took place when proto humans, called Homo habilis or “handy man”, learned the art of making the first crude tools out of stone and bone. With Homo habilis, the rudiments of human technology began its steady climb of complexity to what we have today. Compared to our past, it seems that we are currently in a great age of communication. A thousand years from now, when anthropologists look back on the achievements of 21^st century computer age humans, they might label us “Homo communicatus”.

About 2 million years ago another hominin ancestor called Homo erectus or “upright man” evolved and is considered the first hunter-gatherer to live in social groups. Some 1.5 million years ago this group apparently was the first to learn how to control fire and use it for cooking, as well as the first to make clothes out of animal fur.

As family and social groups grew – the average being about 40 individuals – symbiotic, collaborative relationships developed in which each person learned a skill that contributed to the well-being of the entire group. Some became tool makers, some were hunters, while others helped with food preparation and caring for the sick and elderly. Through group interactions, individuals learned from each other, especially after the development of a new phenomenon: the ability to communicate using language. Once our ancestors were able to turn their squeaks and grunts into meaningful words, human communication was established and the evolution of cultures progressed rapidly.

It is interesting that when we look at the time frames involved in human evolution, we speak of millions or thousands of years. These are time frames that many in today’s world find hard to grasp. For example, the world was much different in as short a time as 2,000 years ago, and many of us are hesitant to predict what we humans might be like in the next 2,000 years. These are very short lengths of time evolutionarily speaking, but given the pace of life today, especially our pace of technological achievement, even these short time frames mark profound changes in human development.

By the time we had evolved into Homo sapiens, “knowing man”, roughly 250,000 years ago, we had developed a primitive human consciousness. We became aware of ourselves as separate from other animals and that each of us had a separate identity with our own particular likes and dislikes and outlook on life. But in spite of our differences, we had enough in common that we learned to live in larger and larger organized groups that eventually became cities and nations. We had evolved a sense of morality and a sense of treating each other fairly that greatly facilitated our human development.

As our human consciousness grew, we moved into our third major phase of evolution. We began to move beyond animal instinct into an ability to solve problems by reason and logic. But even as our ancestors evolved into more cooperative human beings with the ability to communicate through spoken language, they drug along many of the instinctual behaviors that had gotten them through the challenges of natural selection.

Early in our evolution the primary emotion was fear. Is that sound behind you leaves rustling or an animal ready to pounce on you? Your heart races, your muscles tense and the amygdala, the fear center of the brain, takes over. Do you turn ready to fight, or run, or stand there frozen in fear? Even today, in many nations around the world, if an airplane flies over, people are cautious. Is it friendly or will it drop a bomb or shoot a missile at us? We have lived with fear since early in our evolution. And, given the number of weapons in the world and the instability of the people who own them, we still must make fear a part of our lives.

Fortunately, at the same time we were learning to live with fear, we humans were also developing a sense of love. It is believed that the emotion of love grew out of the care and nurturing of parents for their offspring, which early in animal evolution may have been little more than an instinctual motivation to carry on the species. But the emotion became important in the evolution of birds, mammals, and us.

Today love is probably one of the most overused and misused words in our vocabulary. From “love thy neighbor”, to “let’s make love”, to “Oh, I just love chocolate”, love is a word that can covey a myriad of meanings and emotions. The good news is, however, that in all the ways love is used, it generally denotes a positive and happy state of mind. We’ll certainly take any of the uses of love over hate.

So now we come to our fourth evolution. For much of our history, we have acted as if we were under the control of two forces, one natural, the other man made. Naturally, having evolved from animals, we have maintained many animal traits and instincts. Many animals survive by aggressively eating other animals, thus fostering fear in the animals they prey on. An antelope must be cautious when a lion is nearby. On the other hand, the aggressive lion uses stealth, and brute power to overcome the antelope. Our ancestors learned these traits and passed them on through the generations.

So, as we evolved, we learned to be fearful and cautious about things around us, including other people who we do not know and trust. We also learned to use what stealth and power that was available to us, from claws and teeth to arrows and spears, to missiles and bombs. The tendencies to be fearful or aggressive have followed us down through the ages and have manifested themselves in numerous conflicts and acts of aggression.

As we understand more and more about the progression of our evolution, we have come to realize that wars and conflict are detrimental to our progress as we continue to develop our human consciousness and move away from merely instinctual behavior. More than any other human behavior, conflict among people and nations shows us that we still carry the traits of fear and aggression that strongly influence the lives of many animals. We, as humans, must evolve ourselves beyond these.

Another hindrance to our human development was that, lacking the factual information that science gives us today, our early ancestors tended to grasp at quick answers to their most profound questions concerning life, death, and the challenging environment. They sought answers largely through religion, which gave comfort when they believed that deities more powerful than themselves controlled life’s circumstances. Years ago, and even among some people today, it was thought that praying to a god and offering a variety of sacrifices that ranged from bread to animals, and in extreme cases, to our fellow humans, would appease the gods and bring us happiness and prosperity. Also, our creative and impulsive minds came up with a plethora of mythologies that explained the origin of the Earth and how we came to be as we are. Many of these myths wound up in written collections that some consider ‘sacred’.

For many years we accepted our religions and myths as truth. Also, for many years we believed that the sun and everything in the heavens revolved around the Earth and that our gods were so powerful that they made Earth, and us and everything in the cosmos. The longer we told our myths to each other the more we came to believe them as truth. Some of the most devout came to consider their gods infallible.

Then over the years a few thoughtful people began to take a closer look at our natural environment and how we interpreted it. One of the first to propose the idea that all matter is made up of tiny particles was a Greek named Democritus, who, lived from 460BC to 370BC. He named these tiny particles atoms. It was a pretty wild idea for the time when most people believed that everything had been made by Zeus and the other Greek gods.

His idea lay dormant for several centuries until the early 1800s when British scientist, John Dalton, did experiments that proved that atoms exist. We now take atoms for granted, as we do the fact that the Earth and our companion planets orbit the sun.

It took thoughtful and brave people to begin to pull us out of the religiosity of the medieval years when most of the western world was ruled by the Catholic church. The transition was led by Copernicus, Galileo, Descartes, Newton and others who, although not ready to completely abandon the old faith of the past, nevertheless set the tone for the enlightenment humanism to come.

Now with science as our guide, we are entering into our fourth phase of human evolution. We have a better understanding of ourselves and the universe we live in than at any time in our past. For thousands of years, we have been pushed along by natural selection which determined our response to environmental factors. And we brought along through our evolution the animal traits and instincts from our mammal ancestors. And since we still had unanswered existential questions, we also drug along our religions. But today our minds have developed to the point that we understand that our future need not be determined by our past nor influenced by gods or other unnatural forces external to ourselves.

This is new. We have never considered ourselves to be on our own before, although, in actuality, we have always been on our own. We just refused to accept it or believe it. We had enough intelligence to cope with environmental challenges and the challenges of procuring an adequate amount of food. But since our minds were still developing beyond our primate ancestors, understanding our origins and such things as the sun, moon, stars, life, and death required an intelligence greater than what we felt we had at that time. It was this lack of self-confidence that drove us to invent gods and mythologies to explain ourselves and the world around us. And as our various creation stories were passed down through the generations, our fictions became our facts.

But that was then, and this is now. Science has completely changed our perspective on many of the issues that caused us so much anxiety in the past. Science explains to us the origin of the universe, the evolution of life on Earth, and the possibilities that await us in the future. Where we had fiction, we now have facts.

Those not ready to give up the old system of beliefs say that science with its theories based on solid research and observable evidence, has little impact on human moral and ethical behavior. The idea that the scientific illiterate espouse is that science is too objective to relate to the foibles of human behavior. But when one looks deeper, it is evident that science does indeed give us a firm moral base to live by.

Science teaches us to look inside ourselves and understand that we are all one people wherever we live. We are not products of a plethora of gods but of natural processes and materials that had nothing to do with God, Allah, Zoroaster or any other mythological deity. We are all citizens of our planet in one of many solar systems in one of many galaxies, and we are all made of the same elements that are created in stars from the same protons, neutrons, and electrons found throughout the universe.

One could argue that our national loyalties have been important to us in shaping our current civilization, but our world of 8 billion people and growing, should not be a world of splintered factions in conflict with each other. Science points out that at our core, we are all completely the same. We are one race, and one species, and when the old ideas of religious, national, cultural, and racial differences fade, we will no longer have those reasons for conflict. We then become one people. Not as mindless ants in a colony, but freely interacting individuals who share a common morality, who deal honestly with each other, and who are free from the biases that foster antagonisms.

Thus, through science, the universal morality that religions claim as their domain, can be seen as a trait that humans have always had but did not manifest. Perhaps we were too preoccupied with survival needs such as food, shelter, and security to think deep enough to recognize the rise of our human consciousness and sense of morality. Then, as now, getting through the day sometimes did not leave much time for introspection.

For some of us in years past, and unfortunately, as it is for too many of us now, it was just easier to let others make our existential decisions for us and set our moral standards. Yet, without a strong inner core of compassion and concern for others, and an innate drive to keep the species progressing, Homo sapiens would not have lasted long. This drive manifested itself as love for our offspring and was the basis for the emotion of love as we experience it today. As we evolved, love for offspring and kin grew to include love for others in our community. The emotion continues to be strong in us.

Now, after thousands of years of human evolution, science is giving us back us our human dignity. We are finally beginning to understand that we ourselves, each one of us, has the ability and the responsibility of making our own decisions and cultivating the sense of morality within ourselves. As we become more thoughtful and introspective, we are beginning to move away from the idea of spiritual entities that we imagine in everything from rocks to clouds controlling our lives.

As a result, we find ourselves today in a state of transition that has both good and bad repercussions. Today there are dictatorial governments which have replaced the worship of deities, which shows human progress. However, they have replaced the worship of a supernatural deity with the worship of state or outright worship of a dictatorial ruler. These nations have become institutions of sycophants where opposition by citizens who seek a modicum of freedom of thought is often punished by imprisonment or death.

These throwbacks in our progression of human evolution remind us that many of us are certainly not fully evolved and still choose conflict and aggression over global harmony and morality. It is unfortunate that the backward thinking rulers of these oppressed states set the standards for the nation’s morality. The dictator and his or her sycophants demand obedience often with life-or-death control over the lower ranking citizens. State-based morality is certainly no improvement over religion-based morality, and we must move past both of these as we develop our human-based morality.

The important step beyond both state-based morality and religion-based morality is the sincere morality practiced by humanists and others who have an innate concern for the well-being and happiness of others yet who do not profess any religious affiliation. They realize that concern for others certainly does not need to be externally based. It comes from within the person, not from a religious or political directive.

We now understand that our fourth phase of evolution toward a more cooperative and peaceful world in which our behavior is based on high moral standards is a process that involves being aware that morality comes from within the person and is not religious based or state based. Although some religious people through the years have advocated peace and harmony in human relations and have attempted to set a good example, humans do not need a priest, rabbi, imam or anyone else to tell them how to be moral. Each one of us can look within ourselves and resolve to treat others as we would be treated. Do not lie, do not cheat, do not foment hatred. Set a life course of high morality and integrity and be happy with the path you are on while you are always striving to be a better person.

As much as anyone on Earth you can be a person who moves us forward in our evolution toward a peaceful world; a world where discord and conflict brought on by power hungry dictators and criminals is considered nothing more than a sad relic of the growing-pains we experienced in the adolescence of our evolutionary journey.

Given the spate of confusing news we get daily, some of us feel helpless and inadequate to do anything to help heal our factious human civilization. But keep in mind that you are important. Just by being a moral, caring, and honest person you are setting a good example for others to follow.

You are in control. Your future is yours, and for all of us, our future is ours. Our future does not belong to imaginary deities, nor does it belong to spite-spouting demagogues who stir up discord only to appease their insatiable ego. Your future is what you thoughtfully want to make it. Be always mindful that you are an important part of the evolutionary journey we are all on. Be kind. Do your part to help establish harmony and cooperation among all people.

We humans are a young species, still evolving and still learning. In time, we will evolve ourselves past our tendency toward conflict and aggressiveness.

Ted McCormack