Vestigial structure is a structure in the organism's body that has no longer use for the modern resident, but crucial in their ancestor's lives. For example, the tail bone of humans or the pelvic bones of whales. These structures don't affect our daily lives much, however, they carry the evidence of common ancestry between every living organism on earth. For example, the tail bone of ours indicates that we evolved and had a common ancestry with monkeys, who still have their tails now, but because of an evolutionary split, we no longer need this structure. And as for whales, the pelvic bone is the evidence of what they evolved from---dog-like organisms who lived near the water,and as they slowly turned their habitat in the water, they abandon the structure of the back limbs. By using vestigial structure which still remains in our body, we can implement the science investigation to study common ancestry and heredity between organisms on the planet, better acknowledging the connections or lives. We can also use vestigial structures to acknowledge the structures and functions we had in the past, but disuse during the process of evolution.
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