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A vestigial response or vestigial reflex in a species is a response that has lost its original function. In humans, vestigial responses include ear perking, goose bumps and the hypnic jerk . In humans
Goose bumps are an example of a vestigial human reaction to stress. The formation of goose bumps in humans under stress is a vestigial reflex; a possible function in the distant evolutionary ancestors of humanity was to raise the body's hair, making the ancestor appear larger and scaring off predators.
In humans, the vermiform appendix is sometimes called a vestigial structure as it has lost much of its ancestral digestive function.. Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. [1]
The formation of goose bumps in humans under stress is considered by some to be a vestigial reflex, [4] though visible piloerection is associated with changes in skin temperature in humans. [5] The reflex of producing goose bumps is known as piloerection or the pilomotor reflex, or, more traditionally, [6] horripilation.
The postauricular reflex is a vestigial myogenic [5] muscle response in humans that acts to pull the ear upward and backward. [6] Research suggests neural circuits for auricle orienting have survived in a vestigial state for over 25 million years. It is often assumed the reflex is a vestigial Preyer reflex (also known as the pinna reflex). [7] [8]
The grasp reflex also allows young individuals to have more developed food manipulation and dexterity skills. This suggests that the grasping reflex is vestigial in humans and in other non-fur carrying primates. [11] The reflex is also suggested to create a basis for which the voluntary grasping action originates.
This reflex formation of goosebumps when cold therefore has a useful function in humans with thick body hair, but the reflex to form them under stress is vestigial. No source is cited to provide evidence that even “particularly hairy humans” are hairy enough to trap a sufficient volume of air to be considered an efficient thermoregulatory ...
Certain sounds, such as fingernails drawn down a blackboard, cause strong feelings of aversion or even fear in most humans.A 2004 study claimed that the blackboard sound was very similar to the warning cry of Siamang gibbons and hypothesized that a vestigial reflex is what causes the fight or flight reaction in humans. [3]