We may think that as humans we have reached the pentacle of evolution and that there is no more possible changes we can undergo. However this sort of thinking is misleading. We today are still undergoing evolutionary changes. These changes might be small or insignificant at the moment but they are changes that are still pushing us ever closer to a more evolved form of ourselves.
When we get a fever or have a bad cough the most common reasoning behind this is that we are sick. Illness to most is believed to have been caused by some external force such as bacteria or a virus. While this is true that external forces can and do affect us. It is how our bodies respond to these forces that is unique. If we for a moment view these so called illnesses as perhaps evolved defenses we can appreciate them more and see that we are indeed still evolving. A fever raises our body temperatures well above normal. Yet this carefully raise facilitates in the destruction of pathogens. Research has been made to show that cold-blooded lizards when ill move to warmer places in order to raise their body temperatures. Those that cannot find a warmer place to raise their body temperatures are at an increased risk of death from the infection they carry within. A cough can also be seen as an evolved defense. A cough if viewed as defense trait shows a greater cause than simply an annoying gesture. When we cough we are attempting to expel and clear the lungs of any pathogens, dust, or pollutions that the body does not recognize as normal. In this sense we can see how a cough is an effective adaptation that we have acquired in order to better help us ensure our survival as a species.
When looking at behavioral traits that we as humans have there are some that might deem as unnecessary or undesirable. Consider the trait anxiety and the perceptions it carries. This trait could easily be said to have originated as a defense mechanism in response to dangerous situations. This trait promotes the urgency of escape and avoidance. A study by Lee A. Dugatkin evaluated the benefits of fear in guppies. He divided the guppies into three groups the timid, the ordinary, and the bold. He then placed a smallmouth bass within each group. The timid hid, the ordinary simply swam away, and the bold stood their ground and eyed the bass. Each group was then left alone with the bass for sixty hours. After this time period the results showed that 40% of the timid survived, 15% of the ordinary survived and the bold had been completely ate. This experiment showed how fear or anxiety served as an excellent defensive trait that ensured survival. While it may seem as a bothersome thing to have today, this trait has helped human evolution by allowing us to survive and pass on our genes to the next generation who might also be needing the same traits to survive this harsh world.