atavisms......

Atavism is the reappearance of a characteristic in an organism after several generations of absence, usually caused by the chance recombination of genes.

In humans, these evolutionary throwbacks may include vestigial tails, large canine teeth, extensive hair growth on body, supernumerary nipples and face and extra - or webbed - fingers and toes.

The best-known vestigial organ in humans is the appendix. The original function of the appendix, which can still be observed in many herbivorous mammals, is "as a fermenting vessel ... containing bacteria that help the animal break down cellulose into usable sugars."

As we have a more varied diet nowadays, we don't need the appendix. In fact it can be a real nuisance !

Another vestige of our past is goosebumps, which we get when we're cold or feel threatened but are basically useless. But in mammals that actually have fur, raising that fur would be useful to insulate from the cold or to appear larger when threatened – exactly the same two situations.

Another example can be a tiny, almost imperceptible point on the outer rim of the ear known as Darwin's tubercle. Only 10% of the population has it. Darwin's tubercle demonstrates our common ancestry with other primates, which have significantly more prominent pointed ears, possibly to help funnel sound into the auditory canal. Example: human ear with the point, a macaque's ear and an example illustration from Darwin's The Descent of Man