The Evolution of the Human Brain:
How it Differs From Our Ancestors and Why?
The human brain is a feat of evolution: it has allowed humans to have complex thoughts, conscience, build tools, create fires, and much more. Humans did not acquire this simply by chance. Evolution throughout our ancestral past has shaped and moulded the human mind to its state. The earliest of ancestors, including apes, had very small brains, but as evolution progressed, so too did the human brain. The rapid progression of human intelligence has been attributed to environmental changes causing humans to change with their surroundings for survival. This lead to the expansion of specific areas of the brain, vastly differing maturation of humans compared to our ancestors, changing genetics, which is just some of the changes that has occurred in humans. In this present paper, the changes and reasons as to the changes of brain over the course of human evolution are investigated. Research into this topic shows studies similar correlations with respect to one another, with the majority of sharing and overlapping in many opinions on this topic. Majority of research discussed has fairly been recently conducted within the last decade, and virtually all were conducted by western or European researchers. The most discernible change in the human brain is its absolute size. The average brain of the modern human is up to four times larger than of our earliest ancestors. Currently, the average fully grown adult Homo sapiens is approximately 1200 to 1600 cubic centimetres and weighing three pounds. In comparison, the earliest trace of human ancestors, the Australopithecus clan had brains slightly greater than apes, around 400 cubic centimetres. Anatomically the Australopithecus were bipedal akin to humans, but intellectually akin to primates, which suggests that bipedalism preceded the growth of the brain on the timeline of human evolution. The next ancestors, Homo habilis had an increased cranial capacity of approximately 650 cubic centimetres. With this came the earliest evidence of tool-making by a species which has been attributed to increased brain capacity. Homo erectus had a cranial capacity of approximately 850 to 900 cubic centimetres. This increase has been associated with the exodus of the Homo genus from Africa into other continents as they move to track the sources of food caused by the change in climate. The greatest evolutionary bound in brain capacity was that of Homo neanderthalensis with a capacity of approximately 1300 cubic centimetres, which in some cases is greater than that of the average modern Homo sapiens. This may have been a result of Homo neanderthalensis having larger bodies that tend to need increased neurologic control mechanisms. (Hurlbert & Loreto, 2011; McKie, 2000; Davis, n.d.) Homo sapiens, when compared to all other mammals, have the largest brains with respect to their body size. This is measured by the encephalizaton quotient or EQ, which is the extent that the brain size of a species deviates of the “standard” species. For mammals, the standard is a cat, with an EQ equivalent to one, or the “control” standard. The human is seven to eight times larger than expected with primates with the nearest mammal on the list being half of that. (Roth & Dicke, 2005) Increased brain size does not generally equate to greater intelligence; humans do not have the largest brains of all animals. When looking at the brain size, it is also important to look at which parts and sections of the brain that has been expanding. Over the course of human evolution the absolute size of the visual cortex compared to apes, has seen little difference, but the human nonvisual neocortex & prefrontal cortex is larger than that of primates and human ancestors, which allowed for social competencies unique to humans, such as theory of mind, language, and the ability to mentally simulate social situations. (Dunbar, 2007) The prefrontal cortex is the section...
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