WHAT MAKES US HUMAN?

As humans, it is unarguable that we are the most developed and dominant species the world has ever seen. Humans have created cultures and societies that have evolved over millions of years that has eventually enhanced the level of sophistication of modern humans. With our advanced technology, language, social and problem-solving skills, we have manipulated our world in ways that no other organism has ever done. In terms of numbers, there are organisms that are significantly more numerous, cover most of the earth’s surface and make up most of its ecosystem than humans. According to scientists from the University of Georgia, the estimated number of bacteria on our planet is five million trillion trillion. There are far more bacteria on earth than there are stars in the universe. In fact, a million bacteria can fit on the tip of a pin, an incredibly large number. However, humans have evolved to possess abilities that enabled them to manipulate and control the behaviours and lifestyles of other creatures in ways that have shown our superiority and intelligence over other organisms. It gets really interesting when we think about what makes all this happened? What makes human more dominant and advance than other creatures such as our closest phylogenetic relations, other great apes? I was inspired to answer this question by Leonard White, an associate professor in neurology at Duke University, who is also my course coordinator and instructor in Medical Neuroscience at Coursera.

https://mosaicscience.com/extra/does-brain-size-matter

In order to answer the question on what makes us human, we must consider some fundamental aspects of the brain such as the size, structures and connections between those structures, gene expressions and the emergence of novel functions during brain evolution that support higher levels of cognitive functions. The human brain weighs an average of 1,400 g, and 2% of total body weight. By comparison, Gorillas, our closest phylogenetic relatives, brains amount to about one-third of the size of the human brain. The elephant brain weight about 5,900 g- about 4 times the size of the human brain. The brain to body weight ratio in elephants is about 1:800 and about 1:50 for humans. In terms of brain to body ratio, humans have much bigger brains than elephants. Does brain size determine intelligence? Brain size does not necessarily determine intelligence, however, it does provide room for the expansion and development of certain regions of the brain on the cerebrum that are fundamental in the development of higher cognitive abilities such as language, self-awareness and problem-solving skills. It is quite obvious that the human brain is larger as if bigger is better.

https://mosaicscience.com/extra/does-brain-size-matter

In addition to having a large brain size, there are significant connections that exist in the association cortex, regions that are responsible for cognitive abilities. The actual organization of human behaviour goes on at the level of the individual nerve cells and their connections. The human brain contains 100 billion neurons and probably about 100 trillion connections. These neurons are so precisely connected in ways that support intelligence. In comparison to other primates, humans have more fibres connecting some regions of the brain that possess functions typical of humans such as language, reasoning, problem-solving etc.

Studies have shown that the human brain is distinctly different from the brains of chimpanzees and other primates on both molecular and genetic levels. Gene expression impacts almost everything from the development of associated cortical structures, neurons, connectivity to the regulation of brain metabolism. With such differences in gene expressions, it is quite apparent that the human brain is significantly different from the brains of other organisms in ways that make us unique and enable us to be very skillful and innovative while at the same time dictates our susceptibility to both neurodegenerative and neuropsychiatric diseases. We are who we are because of the complex biological functions of our brain and understanding these function and how they are regulated could help us solve problems associated with neurological disorders.