Question

What are the advantages and disadvantages of having a post anal tail?

Answer 1

Many animals can use their tails for various survival purposes. For example, tails are responsible to balance animals front-to-back for easier movement; some animals are able to use them for defensive purposes, some for utility purposes, some are purely cosmetic. The Trex needs its tail to balance off its immense front weight to the back so it doesn't topple forward. Lizards can lose their tails to distract predators.

Since we have evolved to stand upright, the uses of the tail become arbitrary. Whatever tasks we need to perform, we are able to invent tools to do this job. In addition, tails do not provide overall protection; however, most key organs that are responsible to protect our body include skin, skull, spine, rib cage. Due to specialisation and evolutionary niches, we lose our tails by perhaps not walking on grasslands / forest ground.