Human Brain Size

In the course of evolution, humans are known to be the most developed of all organisms. The major catch in their evolutionary history is the increase in brain size and cranial capacity. This helped them to make new advancements and by the use of science and technology, they were easily able to dominate over other life forms. The invention of fire, the wheel, development of language and books are some of the changes man brought into society and helped them to succeed. The thought process and then experimenting upon them is what brought changes into the world. The evolution of humans is studied along the line of evolution of apes. This is because we humans are closely related to apes. The evolution of man and the human brain size can be studied under three subheading that is:

• Prior to the ape man

• Prehistoric men that included ape-men

• Living modern men

In the course of evolution, there was an increased cerebral capacity and increasing brain size. The brain weight in human body is around 1.5 kilograms. We will study these three in detail below. 

Prior to Ape Men

• Dryopithecus: In the Miocene rocks of Africa, the fossils of these species were discovered. It is estimated that they were present 15 million years ago. Their walking style resembled that of gorilla and chimpanzees. There was a lot of hair on their body. They are considered to be the ancestors of modern-day apes. The length of their arms and legs was the same. They had a semi-erect posture. They used to eat fruits and leaves. They had a large brain size and are considered the common ancestors of both man and apes.

• Proconsul: Louis Leakey discovered these fossils in the year 1948. They have discovered around the rocks of lake Victoria that are present in Kenya. They were present in the Miocene epoch. Their forehead was round like the forehead of modern man. The canines were long and sharp. They also had a large brain. 

• Sivapithecus: The fossils were discovered in the Shivalik Hills of India and that's why they are named so. Their forelimbs and skull were like that of the monkeys. The teeth and jaws were similar to the apes. They were supposed to be present in the late Miocene epoch and they gave rise to the next ancestors that were the Ramapithecus. 

• Ramapithecus: They were present in the late Miocene epoch and raised up from Sivapithecus. They were present till the late Pliocene epoch. So they were present around 15 million years ago. Edward Lewis discovered the fossil of Ramapithecus. 

Ape-Men Including Prehistoric Men

• Australopithecus: They are considered to be the connecting link between apes and men. They were discovered by a South African anthropologist. They were discovered in Pliocene rocks near Tuang that is present in Africa. They are thought to have appeared 5 million years ago and lived in the Pleistocene epoch. They used stone weapons for hunting and ate fruits. An omnivorous diet and bipedal locomotion were present in them. The brain capacity was about 500cc. “CC” stands for cubic centimetres and it is a unit to measure the brain capacity or the homo sapiens cranial capacity. This capacity is similar to that of an ape. Brow ridges were present above the eyes and they lived in caves. In their vertebral column, they had a lumbar curve. They also had broad pelvis. Small molar teeth were also present in them. The human brain evolution starts from here. There was an increasing brain size seen from here. 

• Homo Habilis: They were known as the toolmaker or the handyman. They were the first species that looked like human beings. They were thought to not eat meat. They were around 1.5 meters tall and had bipedal locomotion. Bipedal locomotion means that they moved on two legs. The brain capacity was increased from 500cc to around 750cc and that is the reason they were more skilful than their ancestors. They used chipped stones to make tools. They also lived in caves and used to care for their young ones. They were called handyman because of the place where their fossils were discovered, the tools were also found close to their fossils. 

• Homo Erectus: As their name suggests, they were also known as the erect man. They appeared 1.5 million years ago and were thought to have eaten meat. They are also called middle Pleistocene men and were evolved from homo habilis. Their brain capacity was 900cc. Their cranium was present in the shape of a dome. This was to accommodate the large size of the brain. Their posture was erect and the males were larger than the females. They are probably the ones who discovered fire. The tools made by them from stones and pebbles were more elaborate. They had small canine and large molar teeth. 

• Java-Ape Man: Their fossil was discovered in central Java from Pleistocene caves. They were around 1.7 meters tall and weighed around 70-75kg. Their legs were long and erect. When they used to move so at that time their body used to bend a little forward. They had a broader chin and their nose was also inconspicuous. They had thick and heavy skull caps. Their forehead was low and receding. They also had bigger brain size. Their cranial capacity was around 950-1000cc. They had a heavy lower jaw and large teeth. They somewhat resembled the modern man. They used fire for hunting and cooking. Their lips were thick and they were omnivorous in nature. 

• Peking Man: The fossil of the Peking man was discovered in limestone caves. Their body structure was similar to that of a java-ape man. They were around 1.6 meters tall. Their brain capacity or the cranial capacity was around 1000-1100cc. They were omnivorous in nature. Their stone tools were more sophisticated. They also used fire. They used to live in caves and small groups. 

• Heidelberg Man: The fossils of their jaws were found near Germany. They had massive jaws as that of modern apes. Tools and fire were also used by them for various purposes. Their brain capacity was around 1300cc. Their lower jaw had all the teeth and they were human-like. 

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True Men including Living Modern Man

• Neanderthal Man: Their fossil was discovered in Germany. Their faces were prognathous. They used to walk upright and had slightly low brows. Their jaws were receding in nature and had high domed heads. Their cranial capacity also increased and now their brain capacity was around 1300-1600cc. They had heavy brow ridges and their back was humped. They became extinct 30000 years ago and they existed half a million years ago. They were adapted to cold conditions and glaciers. They were skilled hunters. They used to bury their dead bodies with flowers and tools and are thought to follow some religion. They used to wear clothes made from bushes of plants and used to protect their bodies. These caves become their places of camping and gathering. There was an increasing brain size along the course of evolution. 

• Cro-Magnon Man: They were named cro-magnon because their fossils were discovered from Cro-Magnan rocks. They are regarded as the most recent ancestors to today’s man. They are thought to have emerged in the Holocene epoch. They were around 1.8 meters tall and had elevated noses and arched forehead. Their brain size and cranial capacity were somewhat more than that of human brain size. It was around 1650cc. They were somewhat more cultured and educated than the modern man. They were fond of making cave paintings. They are known as the direct ancestor of modern man. They walked and were able to run faster. They were omnivorous and used bows, arrows and spears for hunting. So it is believed that cave art developed around 18000 years ago. They were specialised in making excellent tools and also made ornaments for them. The tools were made up of stones and some were even made from elephant tusks. 

• Modern Man: They are a final stage of human brain evolution till now. They evolved from the Cro-magnon man and are the latest species in the course of evolution. They are also very skilled and have almost the same brain size as that of a cro-magnon man. They have used technology and artificial intelligence for their development. The modern man has gone through cultural evolution and there are many different cultures present in modern-day society. They also practice agriculture and domesticate animals. They have also manufactured poetry and clothes. A question arises: what is weight of brain? The weight of the human brain is around 1.5 kilograms. This is the average brain weight.