The Bubonic Plague: The Black Death

The bubonic plague, also known as the Black Death, was one of the deadliest pandemics in history. While mostly everyone who came into contact with the plague or another individual who was infected would soon become sick and eventually die for the deadly plague. But, there were a select few the didn’t become infected at all or became infected and then over came the sickness. How did some individuals live and most individuals die? This is because of natural selection. Natural selection is the process by which heritable traits the make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generation. It is a key mechanism of evolution. Individuals who were resistant to the bubonic plague were later found to have a rare mutated gene called Delta 32. This gene provides immunity to the deadly
disease. People who are homozygous for the delta 32 gene are completely immune, while heterozygous have partial immunity. It is likely that this life-saving allele occurs as a random mutation and that it was selected for by the devastating black plague epidemics. The first wave of the plague hit Europe between 1347 and 1350, and it killed about one fourth of the population. Those few individuals who randomly inherited the delta 32 gene were favored by natural selection. The plague hit in waves over the next three generations and during these times there was an increase of the delta 32 gene found in the European population. What is the purpose of an emotion? Emotions can be happy and sad and everything in between. Some people have stable emotions that don’t fluctuate very much and other people’s emotions can go from extremely happy to extremely depressed in a matter of minutes. Sadness and depression are two emotions that most people would think that the human species could do without. These two emotions have developed through natural selection for a specific purpose. Sadness is easier to understand then depression. The idea of sadness having a specific purpose is fairly straightforward. People can experience different levels of sadness. In Why We Get Sick, the authors explain that sadness are losses of reproductive resources. It could be family, friends, a mate, money, health, or even reputation, the loss is always of some resource that would have increased reproductive success through most of human evolution. (Nesse & Williams, pg. 216) To my understanding sadness is our bodies’ way of telling us to stop doing what we are doing. It can help us slow down and realize that something in our surroundings is not right. So, having a normal low mood, or degree of sadness, is beneficial to the human species. Like sadness, there are multiple stages of depression.
But, unlike sadness, depression can be passed down to passed down to offspring. Some mild and temporary depression is normal for an individual to experience in a lifetime but sever depression, or manic-depressive disorder, is not. If manic-depressive disorder is not normal and can be a huge threat to survival then why are we able to carry the gene and pass it down to our offspring? The answer is similar to why we experience sadness, “They probably offer some advantage, either in certain circumstances or in combination with certain other genes” (Nesse & Williams, Pg. 218). I believe that the purpose of depression isn’t to drive people to suicide or other extremely low states of depression that are life threatening. I think natural selection favors depression to help people become aware that they need to make some kind of change in their life. It drives individuals to reach a point of happiness again. Even for the people who self-isolate or become unable to connect emotionally with others and get trapped in their depression there is a way
out. Sadness and depression to most would be something they would rather not deal with, but natural selection still favors them. Sadness is a way for our bodies to tell us to slow down or something is not right. Mild forms of depression can be used in the same way, but sever depression can be detrimental to a persons life.