A vestigial trait is a remnant of a trait that used to exist in an organism’s ancestors. The present organism carries some form of this trait but it no longer serves a purpose in the present. An example is the coccyx, or the tailbone in humans. Our ancestors used to have a tail which may have served to help them in movement and in gripping branches when they used to live in trees. This tail structure now exists in humans as a small bone found at the end of the vertebral column called the coccyx.

As another example, when you’re cold or stressed out, your arrector pili are the smooth muscle fibers that contract involuntarily to give you “goose bumps.”

If you’re a furry woodland creature, this can provide insulation (thick, standing fur traps air between the erect hair follicles, helping the animal retain heat), or make you look bigger (which can mean the difference between being eaten and being passed over for less troublesome prey, a particularly good example being a porcupine). Since most humans aren’t hairy enough to fit the “furry woodland creature” bill, our arrector pili provide neither of these benefits. Learn about more human vestigial traits here.


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One Response to “Vestigiality”

  1. Wishes Says:

    Considerably well written blog…

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