Vestigial Evolution

Ranging from anatomical aspects of wisdom teeth and ear muscles to the behavioral palmar grasp reflex and goosebumps, to the molecular pseudogenes, human vestiges are quintessential imperfections of human evolution (Vieth, 2010). Synonymously referred to as evolutionary “leftovers,” vestigial structures are residual features derived from an organism's predecessors that have lost most or all of its ancestral function (“Evidence for Evolution,” 2016). The existence of vestigial structures is often relative to its lack of selective pressures since vestigial structures do not directly cause harm or affect the survival of the organism (“Evidence of Evolution,” n.d.). However, as reflected in the changed and reduced purpose of a fly’s second pair …show more content…
Medically known as cutis anserina, goosebumps are more of a vestigial reflex than a structure that is triggered by a vast range of stimuli such as fear, coldness, or generally, intense emotions (Kampwirth, 2013). In response to these stimuli, the nervous system sends a message to the arrector pili muscles, which causes hair follicles to contract and hair to stand on end, overall appearing as goosebumps (“Why Do We Get Goosebumps,” n.d.). As primitive humans were covered in body hair, and standing of hairs made humans seem larger to predators, which prevented threats and was advantageous for survival (Kampwirth, 2013). Furthermore, in human ancestors, goosebumps provided insulation by trapping air, yet, in modern humans, there is less body hair and the warming effect is practically ineffective (“Why Do We Get Goosebumps,” n.d.). The reflex of goosebumps are no longer beneficial to modern human survival due to environmental changes over time, but it still provides evidence for evolution by exemplifying how human ancestors once had long hairs and utilized goosebumps for intimidation to predators and insulation (Kampwirth, …show more content…
The fully functional nictitating membrane is present in many amphibians, reptiles, and birds, and is used for protection, keeping the eyes moist, and concealing the iris from predators (Rogers, n.d.). Nonetheless, in humans, the plica semilunaris, although vestigial, is not entirely futile as it aids in eye movement and may have some lacrimal drainage functions (Rovira, 2016). As considerable evidence for human evolution, and because humans do not require the nictitating membrane to maintain proper vision or for survival, through natural selection, the nictitating membrane has become a reduced form which is the plica semilunaris (Ashish,