Our Long Lost Tail and 4 Other Vestigial Features

September 3, 2013

• Topical

Vestigial features are body parts, or organs that no longer provide the same function as they used to in our bodies. They can also be the way we react to certain situations or behave. Scientists use them as evidence of our common ancestry with animals still using them with their original functions i.e. evidence for evolution. An example of this in nature would be the ostrich’s flightless wings.

Read on to discover vestigial features that apply to humans!

Wisdom teeth

These are thought to be left over from the days when we had larger jaws that contained more teeth to make it easier to eat plants by thoroughly grinding them down. Now our diets have changed due to eating much more processed food….however we still have wisdom teeth and these can sometimes cause people a lot of pain!

Coccyx

Yes, humankind still have the remnants of a tail inside their body! The tail bone (or to give it its proper name, the Coccyx bone) makes up the very last bit of your spine.

Although we have tails early in our development as an embryo, it is soon absorbed into the body never to be seen again. However, it is not entirely useless, as our coccyx bone still has some muscles attached to it that are needed or walking.

In nature, animals use tails for a variety of things: balance, a source of forward movement (fish), swatting away flies, grasping on to trees… the list goes on and on!

Arrector Pili (also known as Goosebumps!)

Goose bumps originate from tiny muscles called arrectores pilorum that are found at the bottom of our hair follicles. When they contract, it causes the all the attached hairs to be pulled and stand up on end. This is a ‘fight or flight’ controlled by our bodies’ sympathetic nervous system ,the same system that, for example, quickens your heartbeat when under pressure.

You’re probably used to getting goose bumps when you’re cold or scared but have you ever noticed they don’t really seem to help in any way?  That’s because the upright hairs are meant to trap air to create an insulating layer for warmth but we humans don’t have enough hair for this to work! Scientists use this as evidence of our ancestral links to other mammals with plenty of hair to keep them nice and warm.

The Palmar Grasp Reflex

Another quirky vestigial trait is the palmar grasp reflex. You’ll be more familiar with this motion as what babies do when they firmly clasp anything you place in their hands. Scientists think this particular behaviour could also be leftover from our more furry days when young infants needed to cling onto their parents’ backs or tummies to be carried around.

Third eyelid?!

Animals like reptiles and sharks have transparent clear eyelids they use to keep their eye moist while still being able to see. You might be surprised to learn we have the vestigial remains of it in our own eyes except it’s no longer used for protection. It’s called the semilunar fold and it gives our eyeballs greater mobility and helps to carry away our tears.

Can you think of any other weird and wonderful vestigial features?! Let us know.

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