The emotion known as fear, evolutionary biology claims, is an integral part of a person’s survival instinct. Observing animals can easily confirm this statement. Terror at the prospect of being killed and eaten is the driving force behind the gazelle’s rapid dash across the African savanna. Terror of being pushed out of her fertile hunting grounds pushes the lioness to bite and tear into the flesh of the aforementioned gazelle. Fear is just as omnipresent among humans as it is among animals, and in the past, it was just as crucial to survival. Interestingly enough, recent research is starting to show that there is a lot more science to the sensation of fear than most people would believe.
Science has shown that being afraid triggers the fight or flight response in people, but research conducted by the neuroscience department of New York University claim that it does not end there. The body obviously feels the most drastic effects of being terrified or afraid. A host of hormones and biochemicals, like adrenaline, are pumped into every area of the body. These prepare a person, in case the need to physically perform beyond their standard levels are needed. The amygdala, a small section of the brain, is known to be the area that initiates this first response. However, this part of the brain has been shown to react only if the trigger has previously been recognized as a potential threat to status or survival. That implies that another part of the brain is responsible for someone learning fear responses.
According to research, the prefrontal cortex of the brain is responsible for the interpretation of sensory information. There have been some signs that point to this area being responsible for a person learning fear responses. Presumably, all fear is based on sensory information gathered through experience. This would imply that, once a certain stimuli has been interpreted as an unwanted sensation, it causes the person to both subconsciously and actively avoid those sensations. While this does explain why people will avoid being caught in certain situations after having experienced them once before, this does not always equate to a person being afraid of said situation.
The theory also does not explain certain instinctive reactions. Most people grow up afraid of certain things that they have not actually experienced. If the above theory is to be accepted, it must find a way to account for fear responses that appear entirely instinctive and are not explainable simply by previously acquired sensory data. Some experts believe that a combination of several areas of the brain, including the amygdala and the prefrontal cortex, act in conjunction whenever someone is afraid, as well as determining what unknown factors should make a person afraid.
Research done by the University of Wisconsin have revealed that levels of a drenocorticotropic hormone (ACTH) are tied directly to levels of fear. The test used rhesus monkeys as a basis for a human model of the study, which had a notably similar result. The study also shows that there might be a hereditary link between ACTH and fear. The research team found that mothers that were regularly scared, giving them higher levels of ACTH in their bloodstream, had offspring that exhibited the same tendencies. The offspring of the scared rhesus monkeys had higher stress and ACTH levels than others, suggesting a possible genetic link in ACTH production.
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* Hank gets real with us in a discussion of evolution – it’s a thing, not a debate. Gene distribution changes over time, across successive generations, to give rise to diversity at every level of biological organization.
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Table of Contents
1) The Theory of Evolution 1:49
2) Fossils 2:42
3) Homologous Structures 4:36
4) Biogeography 7:02
5) Direct Observation 8:52
References for this episode can be found in the Google document here: http://dft.ba/-2Oyu
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Evolution: It’s a Thing – Crash Course Biology #20