Around five million years ago, in the Rift Valley of eastern Africa, a great divergence occurred. A divergence where one species of animal, unwittingly, split into two. From this divergence a few individual animals walked on their four limbs away from the rest of their family. They walked in search of greener pastures, they walked in search of more space to roam, in search of more food, less competition, more opportunity. They walked and they walked and they walked and for whatever reason, they never returned.
They almost certainly intended to return so they could report back to the group their findings, but something got in their way, something prevented them from making the return trip. So instead of returning, they forged onward. They made a life for themselves in their new surroundings, they had children, their children had children and they evolved. They evolved rapidly. In a mere five million years (a blink of an eye in the course of the history of Earth) they evolved from an animal similar to a gorilla to a modern human.
It is clear in the animal kingdom that we, modern humans (Homo Sapiens), stand head and shoulders above all other species. No other animal has evolved past the primitive use of tools, but we left that behind a long time ago and moved onto many greater accomplishments. We fly in planes, we cure diseases, we grow our own food, we keep other animals on farms or in our houses or in zoos.
How did such a relatively small, weak and naked vertebrate rise to the top of the pecking order of the animal kingdom?
Why didn’t this happen to a larger animal like the elephant or the blue whale? Shouldn’t it have been a more ferocious animal, such as the lion? What about an animal with the ability to fly, like the eagle? Or the cunning, highly intelligent, family-oriented wolf?
It’s well known that we are the most intelligent species. Our brains are far more complex and far larger per pound of body weight than any other animal. The very fact that we know this and that we can state this, is evidence enough. But was greater intelligence enough to bring us to where we are today? Is the answer to this question simply that we are smarter? How did our intelligence evolve so far beyond that of our closest cousin, our great divergence counterpart, the chimpanzee?
This is a question that is commonly avoided by scientists. They don’t like to discuss things unless they have evidence, and the evidence is scant. So, I will use this essay to hypothesize, with limited evidence, how it happened.
The evolution of humankind has continued for almost five million years, but the ascent of Homo Sapiens from ape to modern human to the top of the hierarchy of the animal kingdom can be attributed to five watershed moments in time.
The intent here is not to claim that we are better evolved than other animals, but that we are more intelligent and more advanced technologically. There is no method to measure how well an animal has evolved. Clearly the shark is very well evolved, they have survived almost unchanged since before the dinosaurs. Rabbits are also well evolved, as they can reproduce at an astonishing rate, keeping their population high. Ants are the most plentiful animal on earth, so they must be well evolved. Similarly, the chicken - there are more chickens than any other vertebrate on earth – what are they doing right? Success in evolution is purely subjective, however, it seems obvious that human intelligence and technological advancement is far superior to any other animal.
Many people today take our lofty position in the animal kingdom for granted. So much so, that some don’t see ourselves as animals at all. They see us as a superior being, above all animals, possibly in our own category. This essay deals entirely with the scientific side of this story and therefore, it is accepted that we are legitimate members of the animal kingdom. Although it can be debated if we are superior or special, it can’t be debated that we fit into the animal kingdom rank of the taxonomic hierarchy.
There is no specifically-identified moment in time when we (Homo Sapiens) came into existence. It is widely accepted to be about 5-7 million years ago, when something I’ve identified as the final divergence occurred. A divergence, in evolutionary terms, is the emergence of two species branching off from one. Humans and chimpanzees diverged from a common ancestor to become two separate species. I am calling this the final divergence because there were many previous divergences - such as the point in time when gorillas branched off from the human/ chimp common ancestor, but none since.
Speciation (the creation of one or more new species) occurs when a species separates, or diverges, into two or more groups, never to cross paths and interbreed again. The two groups go forward in distinct locations, reproducing and taking on their own specific characteristics. Just as a baby will have characteristics inherited from his or her parents, these two groups of animals will begin to develop their own characteristics until they become unique enough that they would be considered entirely different species. This process can take from thousands to millions of years, and it happened to us and the chimps.
The common ancestor to chimps and humans, an ape that would look very similar to gorillas today, existed on the plains of Africa millions of years ago. Something happened one day that caused the population of this ape to be separated into two groups. Possibly, while travelling in search of food, they came upon a large geographic divide such as a river. Standing at the river bank and looking across, half of the group made the decision to cross, and half did not. Their intention may have been to reunite, but it never happened.
After the crossing, there became two separate groups of animals, one that evolved into humans and one that evolved into chimpanzees. Over the next five million years the human group evolved dramatically into what we are today: more upright, taller, less hairy, weaker, more intelligent, better able to speak, and eventually, walking on the moon.
What happened to the human group after the final divergence that didn’t happen to the chimpanzees? How did we evolve into the predominant animal in the animal kingdom while the chimps did not? We had all of the same genes. If the changes were genetic, wouldn’t they have happened to both groups?
Was it chance? Was it planned? Or was it the result of good fortune and hard work?
I don’t believe one can make the argument that our evolution into the advanced animal we are today happened before the final divergence. If it did, wouldn’t chimps be the next most advanced animal? The changes would have been happening to them simultaneously.
While chimps are among the most intelligent animals, they are not able to build houses, drive cars, or communicate complex ideas better than a whale, a beaver or an octopus. In fact, despite the chimp’s built-in advantages of high intelligence, grasping fingers, opposable thumbs and ability to stand on two legs, they have advanced no further than these other animals. I would therefore argue that human ascendance to the top of the hierarchy occurred after the final divergence.
So how did it happen? When the group of common ancestors that crossed the river got to the other side, did they have an epiphany? Perhaps the bravest, most fit and most persevering members of the group made it across, and went forward giving birth to brave, strong, persevering children.
Perhaps, it was the human ancestors that didn’t make it across. Maybe the chimp ancestors made it across. Maybe the most intelligent members decided the river was too dangerous, so they stayed behind and gave birth to many more intelligent children who evolved into what we are today.
Ultimately it is not relevant if the human ancestors made it across the river or if the chimp ancestors did. Or if it was a river at all. It could have been a mountain range or a desert. What is relevant is that the two groups experienced a stark difference in the way they evolved after the final divergence. This essay hypothesizes the events that caused this tsunami of evolution.
It is often thought that our intelligence is what set us apart from other animals. High intelligence certainly was a factor. There is no question that intelligent animals have an advantage over dumb animals. Dogs don’t jump off cliffs, bison do. The dogs survive; the bison that make the jump, do not. However, on the open savannahs of Africa, where we evolved, being the most intelligent had limited advantages. It was more advantageous to be big, or fast, or to have very sharp teeth.
There is also no question that hands, fingers and thumbs offer an advantage in the animal world. All primates share this advantage, and some animals, such as bears, do well simulating hands with their front feet. Consider an intelligent animal with no hands - it’s hard to imagine a dolphin developing technology without hands, even if they had the know-how to do so.
The ability to walk on two legs, freeing the other two limbs to act as arms is also a major advantage, enabling an animal to pick the fruit from much higher on the tree thus assuring it can feed itself. Alternatively, the wild boar that can’t get up on its back legs may starve, or relegate itself to eating grass in the field for the rest of its life.
All three of these advantages: intelligence, grasping hands, and the ability to walk on hind legs are shared by all primates to different degrees and were shared by the common ancestor to humans and chimps. Yet somehow humans ascended far above the others. So there had to be something more.
I would also like to rule out all developments that have occurred since the dawn of history. The dawn of history (or the end or prehistoric times) is marked by the development of writing, about 5,000 years ago. By the time writing was developed, we were far along the path to technological predominance in the animal kingdom. Whatever it is we are trying to find happened before this time. So, we are not looking at the great inventions of history: writing, the wheel, steel, the printing press, electricity, medicine. These were all invented as a result of our evolution into the advanced animal we are today.
So, what was it that caused the human technological evolutionary explosion?
Early in this essay, I mentioned five watershed moments. I am hypothesizing that the cause of the human evolutionary explosion between the final divergence and the invention of writing was launched by the cumulative combination of these five events. Each of these five events began with a ‘eureka’ moment setting off a chain of technological developments that set us on the path to where we are today. In some cases, it was accidental, some not. I will discuss them in chronological order.
Event #1
Somewhere in the Rift Valley of Africa four million years ago, a woman who had been gathering nuts all day to feed her children, was sitting on the flat rock of a limestone beach beside a lake. She had collected hundreds of nuts that day and was now spending an hour or more removing the tough outer shells. This process was very hard on her fingers and she was suffering from broken nails and raw, sore finger tips. Attempting to pry open one more shell, the nut slipped out of her hands and landed on the ground beside a fist sized rock. Frustrated at her clumsiness and at the pain she felt in her fingertips, she picked up the rock and slammed it onto the hard shell of the nut. She was surprised and delighted to see the shell explode revealing the plump nut inside. She picked up the nut and ate it quickly. Realizing the power of her discovery, she spread another handful of nuts on the ground and proceeded to smash the shell of each one with the rock. She motioned for her family to come over and share the fruits of her labour. Each of them scooped up the nuts and filled their mouths.
In the woman’s mind, she had simply found a better, faster and easier way to separate shells from the nuts inside. What she didn’t realize, was that she had just set off a four-million-year chain of events. She launched an explosion of human technological evolution. She had propelled humankind into a position where we were ready to leave all other animals behind and begin our ascent to the top of the animal kingdom. It was at this moment in time that the tool was invented.
We are not the only animal to have discovered the tool, and there is no way to know if we were the first. Otters use stones to smash open clams. The great apes all use rudimentary tools. We do not have an exclusive patent on the use of tools in the animal kingdom, but this event set off a chain of tool usage and tool development performed exclusively by human hands. Over time, various materials were used to make tools of various shapes and sizes. In addition to stone, wood and bone tools became common. Tools were used for smashing, prying, scraping, filing among many other uses.
Eventually tools were used to make arrow heads and spears, which were tools themselves, that enabled us to hunt large animals, thus feeding more people with food containing more fat and more protein. This allowed for increased population, as it was easier to feed large numbers of people. These new foods also promoted brain growth which was crucial for higher intelligence.
Today we can walk into any Home Depot and find the tool section, which is one of the most popular and elaborate sections of the store. Human use of tools has set us apart from most other animals. Our use of elaborate tools has helped launch us to the top of the animal kingdom.
So, why didn’t the otters, chimps and other primates develop tools like we did? They never got beyond the smashing, prying and scraping stage. At the time tools were invented our genetic code was virtually identical to that of the chimps. Was it because that one woman was more free thinking and creative? Was she more curious, more fortunate, or more intelligent?
Event #2
A summer storm was fast approaching on the African savannah. A tribe of people, aware of the incoming rain and lightning, were forced to take shelter under a group of thick trees. Suddenly a flash of light and a deafening crack ripped from the clouds. A bolt of lightning had hit a tall tree some distance away. Fortunately, the people were not under the tree that was hit, but they did watch as the lightning lit the tall tree on fire. The storm passed as quickly as it arrived and there wasn’t enough rain to extinguish the fire. The curious people walked over closer to the burning tree to get a closer look. They were taught to fear fire, but also noticed, this time due to the wet ground, that it did not spread quickly. So, they got closer than they normally would, but not close enough to touch it. From a distance the warmth felt inviting. One young boy, a little more curious than the adults, reached for a branch that was on fire. He picked it up and began to walk around with it, waving it through the air, the fire was bright and left a trail of smoke in the air. Then holding it downward he lit a small patch of grass on fire. Another child approached with an unlit branch, held it to the fire on the ground and it ignited. The elders of the tribe warned the children to be careful, but they also stood back and watched in amazement as perhaps the most important discovery in human existence took place before their very eyes.
The mastery of fire was probably the most significant development in the history of humankind. Fire had been discovered long before this day, but it was the mastery of it that set us apart. The ability to light it, manipulate it, utilize it and perhaps most importantly, extinguish it, is what allowed the people of the time to take a massive leap ahead of all animals. To this day most other animals fear fire. A person with fire in his or her hand can scare off a lion. They can use it to keep warm at night, cook their food and ward off a pack of wolves, all with one fire. With fire in our control, we were off to the races in our trajectory to the top of the animal kingdom.
Event #3
The massive mammoth angrily charged over a hill ahead of the hunters. They had already pierced its hide with one spear, but this wasn’t enough to bring it down. Two more hunters were at the bottom of the small hill perhaps unaware that the mammoth was about to trample them. The first hunters called out a warning so the men below would be prepared. Hearing the call, the men readied their weapons and hit the mammoth fatally with two spears to the chest.
All animals communicate in one way or another. A dog barks to warn off intruders. A bird sings, a lion roars, a whale pulses and groans through thousands of miles of ocean. All of these are methods of communication. But there is only one animal that can communicate complex ideas – us. Today, we have many methods of communicating complex thoughts, but in the beginning, there were none. We communicated in ways similar to the animals around us - grunts, yells, waving of arms, pounding our chests. It is thought that the first words were probably used when hunting. Of all human activities, hunting was the one where language offered the greatest advantage. To take down a mammoth required several hunters spread over the terrain. If they could holler to each other, and if they understood what the holler meant, it provided an advantage over the massive beast they were tracking down.
Beyond hunting, people would have learned the power of speech for various other purposes. Years on, a rudimentary language would have developed. The development of language was a key advantage in our ascension to the top of the animal kingdom.
It is unclear exactly how much whales are saying when they call through hundreds of miles of water. What do orangutans say to each other? How do the wildebeest of Africa tell each other to watch out for the crocodile in the river? None of this is well understood. Perhaps they are communicating more complex messages than we know. One thing is clear: the ability to pass messages quickly across large spaces was a key to human evolution.
Event #4
One evening, after sunset a group of families sat around a fire cooking their kill of the day. In addition to cooking their food, the fire offered warmth and some protection from wild animals. Nearby, a pack of wolves circled at a distance. The wolves could hear the people and smell the meat. They were hungry. Wolves have a gene that gives them a friendly and benign demeanor when the situation calls for it. This gene is even more prevalent in domestic dogs today. There was one wolf in this pack, probably the alpha male, that had a mutation in its gene sequence that made it even more friendly than the other wolves. The alpha wolf approached closer than the rest of the pack. Slowly easing itself within view. The people jumped at the first sighting, shocked that a wolf would be so bold as to come this close. The strongest member of the human family lunged forward to protect his clan. The wolf backed up and did not challenge. It remained submissive. The man didn’t have time to drop the meat he was cooking so he stood with it in his hand. Noticing the wolf’s non aggressive nature he decided to offer up a piece of the cooked meat. The wolf gladly accepted as the man lay it on the ground and quickly backed up. The wolf gulped down the entire piece, paused, took a step forward and sat down. It looked up at the man and made extended eye contact. Almost as if it was asking for more. The man offered a second piece of meat. The wolf accepted. At that moment in time, the domestic dog was born.
The domestication of animals was a giant leap forward in the ascent of humankind. With a family of wolves joining a family of people, the people no longer had to worry about a bear visiting them in the night. The wolves would keep people safe and help them hunt.
What humans lacked we could compensate for by keeping an animal that was adept at those tasks. People are weak, horses are strong. People are slow, dogs are fast. Dogs are fantastic hunters, they have a keen sense of smell, and they are aggressive – very few animals will challenge a dog, especially a family of dogs.
There is no other animal that has domesticated another species, this human development is unique to us and it set us ahead of all other animals in our ascent to the top of the animal kingdom.
Event #5
Around 10,000 years ago a woman stepped away from her clan and sat herself down to use the facilities of the day - probably a fallen log on the far side of camp, downwind. As she sat there, she noticed a familiar plant growing out of the pile of feces that was sitting below her. She thought to herself that this was strange, she had often seen this plant out in the meadows and it was rich with food that they could gather to feed the family. But how could it be growing here out of the feces of someone from the tribe? All plants grew wild, there was no way for them to grow out of something man-made – or so she thought. With a little more investigation, she noticed other plants growing nearby, also plants that had been consumed by the people of her family. The only plants growing out of the pile were plants that they had eaten. Could there be some connection between eating a plant and growing a plant? There must have been something in the plant itself that was making it through the human digestive system and allowing the plant to be reborn. It wasn’t long until the seed was discovered. This, the fifth and final event led to the development of agriculture.
For over 99% of human existence, we have been hunter gatherers. It has only been since this woman noticed the plant growing from the pile of feces 10,000 years ago, that we have grown food ourselves. After the development of agriculture, food became much more plentiful, the population exploded and people suddenly had more time to develop other technologies. No longer did they have to spend almost their entire day gathering food or hunting. The development of agriculture spawned a massive human technological explosion.
Through these five events, we now know how the human evolutionary explosion began, but we still haven’t established why it happened to humans and not to chimps or any other animal.
Were we lucky? Were we more curious, or more creative? Or, were we something else?
There is little question that human intelligence led to some or all five of these watershed moments. If an animal isn’t smart, it doesn’t think to pick up the fist-sized rock to smash the nutshell. It doesn’t know it can pick up the unlit end of a branch and not burn itself. It never figures out how to build a spear capable of killing a huge mammoth. Therefore, it could be argued that intelligence is the cause of this explosion of evolution.
But chimpanzees were just as intelligent as humans 5 million years ago.
Today the human brain is three times the size of a chimp’s brain despite our bodies being similar in weight. Something happened to cause our brains to grow at an extremely fast rate, while the chimps brain remained much the same size. We shared the same genetic code, we grew up in the same environment, we had access to the same foods and the same opportunities. Why did our brains grow so large while the chimps’ brains did not? Did the size of our brain beget intelligence, or did our newly developed intelligence force our brains to grow? I would argue the former. Our ability to hunt large animals and feed our families with protein and fat rich food, enabled our brains to grow, thus allowing for storage of more information.
However, one more time, why us and not the chimps?
There may never be an answer found, but that doesn’t mean we can’t hypothesize.
Event Zero: The Final Divergence
A group of 30 of the human/chimpanzee common ancestor are walking across an open, grassy, savannah five million years ago. It’s cloudy and it’s very windy, a storm appears to be brewing. As they walk, they are communicating with each other in their own way, grunts and clicks and one syllable sounds.
Eventually they come to a large river, seemingly impassible. Across the river they can see vast fields of green and lush forests. The group huddles to discuss how they can safely get to the other side of the river to take advantage of this opportunity. It is agreed upon that they will send a select few members across the dangerous waters to assess if it safe for all to cross.
Six members are chosen to make the journey; three females and three males. All six of the chosen few are young adults and are among the most fit, most intelligent and most courageous of the entire group.
They wade into the river to begin the dangerous crossing. Halfway across they are up to their necks in rushing water and realize they have taken on a task far too risky for the rest of the clan. Perhaps it’s even too dangerous for themselves, the chosen six. Eventually, they take to swimming and make it across.
As they pull themselves securely out of the water on the other side, they decide not only is it too dangerous for the others to attempt a crossing, but it’s also too dangerous to return. Until the waters subside or until they find a location where the water is shallower, they decide to remain where they are.
Ultimately, they never find the appropriate time or location. The chosen six never return to the tribe. The group remains permanently divided.
Thousands of years on, the group that didn’t cross the river evolve to become the species Pan Troglodytes (chimpanzee).
The six select members that made the risky journey across the river went forth and multiplied, giving birth to many brave, physically fit and intelligent children… and thus cracked the dawn of the human race.
So, we ask why did humans evolve with such a massive technological explosion while the chimps did not? Why did our brains grow three times their original size?
Even though the chimpanzees had the same genetic code, grew up in the same environment, ate the same food, with the same opportunities… they lost the six most enduring members of their tribe. These six elite members of the group spread their genes of curiousity, determination, intelligence and courage through an entire species – Homo Sapien.
Five million years later, perhaps, we all have the genes that were passed on to us by these six individuals. All 8 billion of us.
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This essay is a combination of facts and speculation. The five events happened. The way they happened will forever be left up to our imagination to fill in the details.
The conclusion is a theory developed by me, I’m sure it would be disputed in one way or another by a scientist in the field.
There are other theories on this topic having to do with social networks, communication, chimps and humans living and interbreeding in encampments together and more.
It is my belief, for our two species to be so different, yet so close from a DNA standpoint, there had to be a point in time – a line in the sand where we separated and never interbred again.
Thanks for reading, BT
