16 Signs of Evolution You Can Still Find on Your Body

Tailbone

Human spine vertebra spinal column medical teaching model showing bones and cartilage.edwardolive/Shutterstock

Humans and our closest relatives, the great apes (chimpanzees, bonobos, gorillas, and orangutans), all have a collection of just a few vertebrae at the bottoms of our spines called a coccyx. It’s a remnant of what in many other mammals grows out to become a tail for wagging (dogs), grabbing tree limbs (monkeys), or balancing on top of fences (squirrels). Tails actually go all the way back to our earliest vertebrate ancestors, which is why fish, reptiles, and birds all have them as well. Because no members of what we consider early human species had tails, researchers speculate that they might have gotten in the way when our ancestors began walking upright, according to LiveScience, but we never lost the trait completely: Human embryos briefly develop tails at around four weeks of gestation.

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