It may be a vestigial organ of ancient humans that has degraded to nearly nothing over the course of evolution.

Prior to this, the thymus was believed to be a vestigial organ with no function.

Vestigial organs, or organs that had become degraded and useless as species evolved, made sense for the first time.

There aren’t many known examples of rudimentary or vestigial organs driving evolutionary innovation.

Rudimentary body parts, those that are smaller and simpler in structure than corresponding parts in the ancestral species, are called vestigial organs.