It's not quite accurate to say that certain body parts are "leftover" in evolution. Evolution doesn't work that way. Instead, it's more accurate to say that some body parts have reduced functionality or have taken on new roles.

Here are some examples of these so-called "vestigial" structures in humans:

* Appendix: While once thought to be useless, the appendix may play a role in the immune system.

* Wisdom teeth: These molars were likely useful for our ancestors who ate tougher foods, but they often cause problems in modern humans.

* Tailbone (coccyx): This is a remnant of our tail, which our primate ancestors used for balance.

* Ear muscles: While other mammals can use their ears for communication, we can only twitch them slightly.

* Palmaris longus muscle: This forearm muscle is absent in about 14% of the population and doesn't seem to be essential for hand function.

* Goosebumps: This reflex, which serves to raise hairs on the skin, was helpful for our ancestors to appear larger and warmer.

* Nictitating membrane: This "third eyelid" is present in many animals but is reduced to a small fold in humans.

It's important to note that some of these "vestigial" structures may still have functions that we haven't fully understood.

Evolution is a continuous process, and even these seemingly useless structures may eventually disappear completely or take on new functions as humans continue to adapt to their environment.