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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.
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 sudden startled arm-jerking response sometimes experienced when on the verge of sleeping is known as the hypnic jerk.. The evolutionary explanation for the existence of the hypnic jerk is unclear, but a possibility is that it is a vestigial reflex humans evolved when they usually slept in trees.
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 ]
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 comes from the maturation of higher motor centers, allowing a child to exert more control over the body. [2]
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 ...
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]
A list of reflexes in humans. Abdominal reflex; Accommodation reflex — coordinated changes in the vergence, lens shape and pupil size when looking at a distant object after a near object. Acoustic reflex or attenuation reflex — contraction of the stapedius and tensor tympani muscles in the middle ear in response to high sound intensities.