Well, although human evolution is a very branched process, as in all living things, what species would we encounter if we wanted to look at it in a chronological order? The first representatives of our family were Hominids, or hominids, who had effectively adapted to the woodlands of eastern and northeastern Africa. The hominids we call Australopithecus lived in eastern and southern Africa from 4.5 million years ago to 1 million years ago.
These early representatives always lived near water, whether in savannas or densely forested areas. Three features symbolizing Australopithecines; small brain, big face and ability to walk on two legs. They simply hunted and ate the small animals they killed without cooking them because they did not know how to use fire.
1- The ability to stand on two legs (Bipedalism)
These small and defenseless distant ancestors began to stand on their two legs, while continuing to use trees as shelters to protect themselves from the dangerous animals around them and to sleep in safety. In this way, they established a comparative advantage over all living things living around them. The field of view of an upright human would widen, and he could see his surrounding enemies more easily.
Since his hands were free, he could make and use tools and easily carry the small animals he caught and the plants he collected to the campsite. In addition, an upright Hominid body is less exposed to the burning and upright sun rays of Africa; thus, the cooling process in the body was more effective.
As the hands could do more, their owners became more successful, so evolutionary pressure resulted in the development of a denser neural network and muscles in the palms and fingers. Today, people can do very fine work with their hands as a result, especially the manufacture and use of complex tools.
The ability to stand on two legs, of course, was not something that happened immediately. However, because of all these benefits, the Hominids, who managed to stand on two legs, were able to gain an advantage and survive, and transfer their genes to the next generations.
2- Disadvantages of bipedalism and premature birth
So, is there any downside to walking on two legs? Of course there was. Humanity has paid the price for its wide vision and skillful hands with backaches and stiff necks. Women had to pay even more. An upright posture meant narrower hips, which narrowed the birth canal, and at the same time, babies’ brains were getting bigger and bigger. Death at birth has become a serious problem for female humans. Because their babies had smaller heads and brains, women who gave birth prematurely survived longer and had more children; natural selection thus gave preterm births a chance to survive. Of course,
in this way, compared to other animals, humans were born prematurely before many of their vital systems were not fully developed. A foal can walk shortly after birth, while a kitten may be a few weeks old and its mother may leave it alone while it searches for food. Human babies, on the other hand, depend on adults for help, care, protection and education over the years.
This situation has made a serious contribution to the extraordinary social skills of humanity. Single mothers, with their needy children on the outskirts, had a hard time looking for food for themselves and their offspring. Raising a child required constant help from other members of the family and neighbors, so the whole tribe was needed to raise a person. Evolution thus favored those who could form strong social bonds.
In addition to all this, because humans are born underdeveloped, they are more trainable and more socially related than any other animal. Many mammals come out of the womb like a clay pot from the oven, trying to reshape them will damage them. Humans, on the other hand, emerge from the womb like molten glass from a furnace and can be shaped to an astonishing rate. That is why today we can educate our children to be Muslims or Buddhists, capitalists or socialists, warriors or peacemakers.
3- Original development in the cerebral cortex
We talked at length about the importance of standing on two legs. It was time for the original development of the cerebral cortex, the second important stage in the humanization process.
The brains of the first representatives of our family did not differ much from that of large primates. The smallest brain volume detected in Australopithecus was 400 cm3. But with the upright posture, the relationship of the head with the body took a new position.
As some hominids developed new behavioral patterns, tools gradually replaced natural organs in their daily lives, and these tools, which lightened the load of the body, paved the way for a larger and more complex brain to gain an advantageous position in the natural selection process. People transferred energy from the biceps to the neurons, like an administration that pours money from defense to training. The developing brain, in turn, opened the door to new ways of life. Thus, a kind of action-reaction relationship emerged; Man had taken its place on the stage of history as the animal with the largest brain compared to its body.
4- Evolution of humanoids into humans
We passed the humanoids. It’s time to meet the first ancestor of modern man. Introducing Homo habilis.
4.1- Homo Habilis
Scientists think that Homo habilis and modern humans have a direct link on the evolutionary tree. These earliest specimens of the genus Homo lived 1.8 million years ago in Tanzania’s Olduvai Gorge Valley in East Africa. During the excavations carried out in this region, many representatives of Homo habilis were found between 1959 and 1987.
Physical appereance
In our habilis ancestors, especially the brain and facial shapes were more reminiscent of today’s humans than hominids. Skull bones were thin, brow arches were more prominent. The forehead region of the brain, where the frontal lobe is located, was more developed than that of hominids. The skull, on the other hand, was free of all muscle attachments and gained a more rounded appearance.
The strong chewing muscles and very large molars we are accustomed to seeing in hominids were absent in our Habilis ancestor. In the Habilis, the enamel was thin. The canine was in line with the other neighboring teeth. The molars, on the other hand, were less broad compared to their length.
The foot skeletons of habilis found today are the organs that best prove upright posture. The standing latitudinal and longitudinal curvature is reminiscent of that of modern man. But if we look at the leg muscles, we can say that they are more durable than us.
Brain structure
The mean brain volume in habilis was 660 cm3. In the earliest specimens of our genus, the brain differed from humanoids not only in size but also in structure. For example, the presence of Broca’s and Wernicke’s regions suggests that our earliest ancestors may have had the ability to speak. Broca’s center is a small bump on the left side of the brain near the forehead. It has a connection with the spoken language and is a center responsible for the production of sounds. The Wernicke center plays a role in perceiving and distinguishing sounds.
Tool making skills
Homo habilis could make tools out of stone. They used the sharp-edged lines they carved out of stone for skinning animals, tearing off pieces, or extracting bone marrow. They also used these stone tools to shape pointed sticks. Meat was not the only food source. While the males were generally responsible for hunting, the females were in charge of collecting plant foods.
As you know, an important feature that makes people human is the ability to transfer learned skills and technology to the next generation. Our first ancestors, the Habilis, did not use the tools they made once and throw them away. They carried their tools and weapons with them to the new camp areas where they settled. They paved the way for the cognitive revolution by passing on how these tools were made from generation to generation. Cultural relations have been the driving force for the brain to develop and acquire a more complex structure.
4.2- Homo Erectus
We witnessed the liberation of hands in Australopithecines. In Habilis, these free hands coordinated with a large brain to create primitive technological tools.
So who’s next?
Homo Erectus… that is, the closest ancestor of Sapiens.
While the oldest representatives of Erectus appeared about 1.9 million years ago, the last representatives were with us even 117,000 years ago. Erectus was taller, stronger, and larger-brained than its ancestor, Homo habilis. Their average brain capacity was 900 cm3, and in the last representatives of Homo erectus, this size increased up to 1200 cm3. This increase created a more complex mental structure, thus a more intelligent human form.
One of the best-preserved skeletons of Homo erectus was found a few kilometers west of Lake Turkana in Kenya in 1984. Scientists named him the “Turkana Child”. The skeleton was dated to roughly 1.5 million years ago. The entire skeleton, including its skull and lower jaw, was very well preserved. This was a boy of 10-11 years old.
Where did erectus live
While Homo habilis lived only in the African continent, Homo erectus people successfully continued their lives in every climate and geography from Africa, to Europe, the Middle East, Turkey, the Caucasus and the north and southeast of Asia. Moreover, they did so for so long that they survived for almost two million years, making them the most resilient human species ever. Two million years is not something our species can achieve. It is doubtful that we will still be around in a thousand years.
Turkana boy
One of the best-preserved skeletons of Homo erectus was found a few kilometers west of Lake Turkana in Kenya in 1984. Scientists named him the “Turkana Child”. The skeleton was dated to roughly 1.5 million years ago. The entire skeleton, including its skull and lower jaw, was very well preserved. This was a boy of 10-11 years old.
Where did erectus live
While Homo habilis lived only in the African continent, Homo erectus people successfully continued their lives in every climate and geography from Africa, to Europe, the Middle East, Turkey, the Caucasus and the north and southeast of Asia. Moreover, they did so for so long that they survived for almost two million years, making them the most resilient human species ever. Two million years is not something our species can achieve. It is doubtful that we will still be around in a thousand years.
Our erectus ancestors were primitive at the skull level and modern at the body level. His leg bones were very similar to ours. In 2001, the pelvis of an adult Homo erectus female dating from 1.2 million years ago was found in the Afar region of Ethiopia. This bone showed that, contrary to hitherto popular belief, the women of Erectus had the anatomy to give birth to babies with large brains.
Homo erectus also needed tools like its ancestor Habilis. He had to make various tools to cut, break, smash, extract plant roots and tubers from the soil, or skin animals. He did. He also had to defend himself against other fellows and predators. That’s why he could also produce weapons. But Homo erectus had one difference; He could produce not only tools, but also tools that made tools.
Discovery of fire
Erectus also discovered fire, an important milestone in our cultural history. More precisely, he tamed fire. The oldest example of this was found in a natural cave in South Africa. Hand axes, hearth ashes, and burnt bone remains of animals whose meat was cooked prove that fire was controlled and used by human.
Human beings have been intertwined with this effective power of nature for half a million years. Fire protected from the cold, illuminated dark nights, and provided protection against wild animals. Our Erectus ancestors noticed that the meat of the animals they killed and the vegetable food they gathered tasted better when they were cooked on fire. Moreover, these cooked foods were easier to digest.
Thus, the load on the teeth, chewing muscles and digestive system was greatly relieved. Teeth shrunk, chewing muscles weakened. As a result, the jaw became smaller, the intestines shortened, and so energy was transferred to the enlarged brain. Big brain also meant cognitive capacity and increased intelligence.
These anatomical features were also reflected in the way of life of people. The discovery of fire drastically changed the social aspects of humans. In dark nights and cold weather, they gathered around the fire and had the opportunity to communicate more strongly with each other. They had the opportunity to transfer the events they witnessed in daily life to each other.
Perhaps they danced and sang around the fire and held various ceremonies. They saved themselves from loneliness. Thanks to fire, the psycho-social development of man gained a powerful momentum. The story-telling animal was on the verge of a major revolution. On the verge of the cognitive revolution that brought humanity to an age…
Neanderthals and Homo Sapiens take the stage
About 250-300 thousand years ago, forms in the Homo erectus line were gradually withdrawing from the scene of history and were replaced by Sapiens, who were more developed both culturally and cognitively. In fact, there was no break in this transition period. So much so that it was very difficult to distinguish the last representatives of Homo erectus from the first representatives of Homo sapiens. Intermediate forms have always existed. Thus, as an era was closing, the era of brand new human forms called Neanderthals and Sapiens began.
The search for food sources, tools developed for a better life, the determination of effective weapons and strategies for efficient hunting, and the unending struggle for survival, such as adverse climatic conditions, allowed new human societies to spread all over the world. Natural selection process; the most capable, adaptable, cunning, resilient, and the most advanced communication system favored the large-brained human species. Thus opened the way for Homo sapiens, who would declare himself the master of the worlds.
This was the beginning of an era.
The beginning of a journey full of religions, cultures, nationalities, myths, civilizations, empires and fictions…
The beginning of the incredible adventure of a species that wiped out Neanderthals and tens of thousands of different life forms…
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