Asked by: Anonymous
Tails are used for balance, for locomotion and for swatting flies. We don’t swing through the trees anymore and, on the ground, our bodies are aligned with a centre of gravity that passes down our spines to our feet without needing a tail to counterbalance the weight of our head. If we want to swat flies, we have our hands.
A tail that you don’t use is just another limb that needs energy to grow and maintain and another thing for predators to grab hold of. Natural selection would have favoured those of our ancestors that had smaller tails when they moved from the forests to the savannah. Over the course of the next few million years it dwindled to nothing. We still have a tail for the first four weeks of our life in the womb, but then it gets absorbed and we are just left with the coccyx at the base of our spine, which serves as a muscle attachment point.