final draft - evolution of the human brain

7/30/2019 Final Draft - Evolution of the Human Brain

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Evolution of the Human Brain: How our Brains have Developed, and How it Affects Us

Jasmine Graham

November 28th, 2012


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Our brains have long since been marvelled at. People have questioned the

simplicity, of just a simple mound of fat and tissue could make for such a complex and

complicated machine. How something that takes up only a small percentage of our

overall body weight, requires 20% of our total oxygen intake? How could just a few

electrical impulses, allow us to react to danger in just fractions of a second, and also

allow us to conceptualize the world around us? It truly is a fascinating thing to think

about, though it hasn't always been that way. Our brains have not always been the

powerful tools that they are today. They, like everything else alive on the planet, have

undergone the process of evolution. This evolutionary process has taken our brain

through various stages. Stages that continue to affect us in our everyday lives, and that

can have a profound effect on how we operate every day, and even how our society

runs. This will be explained. Though the ultimate question that is being addressed here

is: what evolutionary stages have our brains undergone, and how do they continue to

affect us today?

Our brain is composed of many different parts. The forebrain, the midbrain, the

hindbrain, and all the sections that make those up. For example, the cerebellum, the

medulla oblongata, and the cerebral cortex, just to name a few; and each of those is

responsible for controlling something in our bodies. Whether it be the regulation of


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body temperature, such as the hypothalamus does, or the control of our inhibitions,

which the frontal brain is responsible for. The various sections in our brains are

responsible for everything from basic motor skills, to complex emotions and rational

thought. But these properties did not evolve all at once. During the course of our

brain's evolution there were instances when we did not have the 'higher' brain functions

that we associate with outward emotion, or objective thinking. The areas of the brain

responsible for our baser instincts, such as breathing and circulation, is thought to have

been the first one to have developed. It is termed thereptilian complex, and will be

the first to be discussed. The second area in our brains we believe to have developed is

referred to as thepaleomammalian complex, also known as thelimbic system, and

is responsible for functions such as emotions. For example, the parental instincts or the

desire to reproduce. Last but certainly not least to develop is the area of the brain

known as theneomammalian complex. Also known as theneocortex. This is the

area of the brain that many regard as what separates us from other animals,

specifically other primates. This is the area of the brain that allows for abstract and

rational thought. All of these together, the reptilian complex, the paleomammalian

complex, and the neomammalian complex makeup a model which is known as the

triune brain.


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The Reptillian Brain

The oldest, and some would say most primitive portion of our brain is the

reptilian complex. A term given to the brain structure because early scientists studying

it thought it to be the domninant structure in both birds and reptiles. Though it is not to

be discounted simply because it was the first to develop. We certainly would not be

able to function, let alone live, if we did not have this portion of the brain. It is

responsible for the functions in our body that are needed in order to maintain life , such

as the regulation of body temperature, unconscious breathing, and maintaining a

heartbeat. Humans also share the reptilian complex with all other vertebrate mammals.

It consists of two hemispheres, and within those also consists of the basal ganglia, the

diencephalon, and the spinal cord.

All of these various components that make up the reptillian complex have

evolved in order to perform some basic function necessary to maintaining life . It is said

to be the area which is in control of all of our animal instincts, and it is fairly simple to

see why, as it gives rise to some behaviours that can clearly be observed in both

human and non-human animals alike.

For example, the basal ganglia is responsible for functions such as: voluntary

motor control, desire to maintain habit, and eye movement, just to name a few. This is

interesting also, because it can be observed in modern humans on a regular basis .


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Humans continue very much to be creatures of habit in all manner of day-to-day life .

Even something as simple as sitting in the same seat every day at school .

The diencephalon, also referred to as theinterbrainhouses the thalamus

(which is in control of consciousness, alertness, and sleep), the hypothalamus

(temperature regulation, hunger, thirst, circadian rhythm), the pituitary gland

(regulates homeostasis, growth, blood pressure, thyroid gland function) and the pineal

gland (production of melatonin, a hormone that regulates periods of wakefulness and

sleep).

The spinal cord is a fairly familiar structure, and an extremely important one. It

is a major portion of the central nervous system, and is responsible for functions such

as transmitting neural signals throughout the body, reflexes, and the conduction of

motor, and sensory information.

While all of these components lend to

final draft - evolution of the human brain

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