Why do humans have no tail but tail bones?

The origin story of useless tailbones.

Although now useless, the human coccyx – commonly known as the tailbone – is still present at the bottom of the spine, a vestige of our tailed ancestors. Long before humans lost their tails, our fish “relatives” had two tails: one fleshy, the other more flexible, like fins. When the animals began to come ashore, the hind fin disappeared, leaving only the other fleshy tail.

A long time later, the apes also lost that remaining tail. These primates no longer need their tails to maintain balance or send social signals; they shift back into balance and begin to communicate through gestures, facial expressions, and tone of voice.

Other shore animals use their tails for functions such as movement, communication, and repelling insects; while fish still maintain fins to move through the water.

As humans, we’re left with only a tailbone – made up of a few tail vertebrae , like the ones you’d see in real tails – for no apparent reason. . The tailbone is neither beneficial nor harmful, it simply lies there, fixed to the end of the spine.

It just lay there and didn’t do anything, ” said Alexander Werth, a biologist at the University of Hampden-Sydney.

Scientists call these evolutionary leftovers ” vestiges: the term comes from the Latin “vestigium”, which means “footprints”. The remains can be quite diverse, from anatomical structures such as bones and internal organs, to physiological phenomena such as goosebumps ; When our hairy ancestors got cold, their hairs stood up to prevent their body temperature from dropping.

Why do humans have no tail but tail bones?
The coccyx, also known as the human tailbone (Coccyx).

Although scientists do not agree on the specific factors, the standard definition of “trace” states that it has no function in the body.

Werth studied the interactions between traits left over from both evolution and embryonic development; They are more related to each other than you think. As embryos, we used to have tails for a few weeks. By week 8 in the uterus, most are gone.

However, not the gene for the tail suddenly disappeared. Structures that seem lost can still appear in humans, because genes are dynamic and can be “on” or “off” . Birth defects sometimes lead to the reappearance of ancient traits in a process known as “re-breeding” (or “reverse”, “backward evolution” ) – revealing the genome of we have a complete record of all evolution so far.

The result of “re-breeding” is that some people are born with tails. The odds of this are extremely rare: doctors say there have been only about 40-59 cases throughout modern history, although the exact number is unknown. The vast majority of these cases later underwent a tail removal surgery, including popular pop singer Ke$ha.

However, research on the human tail in recent years has not made any progress. In 1875, Darwin recorded in his book “The Descent of Man” that ” under rare and unusual circumstances ” humans can ” form a small external structure resembling a tail “. A few years later, Dr. Rudolf Virchow created a system of classifying human tails, but it did not receive much attention.

We now know that a human tail is more likely a sign of defects in the spinal cord , because the skin and nervous system are so closely linked. Our sensory nerves secrete transmitters called neuropeptides into the skin, and they influence physiological development.

At this point, a question arises: can a person keep the tail and still live a healthy life? “As long as the tail doesn’t affect their ability to survive and reproduce, it shouldn’t be a big deal,” Werth said.

I don’t think having a tail is bad, ” Werth added. ” Who knows. If you’re a circus performer balancing on a rope, it might help you keep your balance “!