I
Ion
Guest
They are called only, “vestigial”. Adaptation, yep, thats proven. But the article suggests some “additional” parts.There are lots of animals with useless body parts (we call them “vestigial” because they are vestiges of evolutionary history). Not just the human appendix but the human tailbone, for instance, does not really serve a purpose (although it serves a purpose for other species with tails).
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Some consider the coccyx/tailbone a vestigial bone, but I’v never seen a scenario in which the bone grows back into a tail…