Why Are Some Babies Born With Tails? Where Did This Unique Feature Come From?

Though it may sound puzzling, there are rare cases where human babies are born with tails.

Babies Born With Tails

According to Science Alert, these appendages do not contain any bones and can even span as long as 18 centimeters. Official records as of 2017 have indicated that there were 40 babies born with true tails. These consist of finger-like, boneless, and soft protrusions.

Such tails can easily be removed through surgery. Despite this, these rare cases tend to garner remarkable interest. This is often because such tails are thought to be evolutionary and benign remnants of a distant ancestral relative, WebMD explains.

Those notions, however, are grounded in an outdated theory, Science Alert adds. The realities behind this could actually be darker than thought. Babies born with tails may actually warrant medical attention.

Why Do Some Babies Have Tails?

Per Science Alert, the mystery regarding the origins of human tails starts with Charles Darwin. More than a hundred years ago, Darwin posited that human tails were accidents of evolution or leftovers from a tailed ancestor.

During the 1980s, some scientists embraced such notions. They suggested that genetic mutations could, at times, revert to their historic condition.

A 1985 paper further distinguished two kinds of tails that human babies could have upon birth. The first one is a true or vestigial tale, while the other may have outgrown the tailbone. The latter, which may include bones at times, is referred to as a pseudotail and has been historically linked to birth defects.

Science Alert adds that both kinds could represent the spinal column's incomplete fusion, or spinal dysraphism. This posits that the formation of these tails is not a harmless, regressive procedure but a worrying disturbance in the growth of the embryo. It may have likely resulted from environmental and genetic factors mixed together.

When the embryo is in its fifth week of development, a tail-like feature sprouts. This structure consists of a notochord and a neural tube. In the eighth week, the tail is usually reabsorbed into the body of the embryo. Hence, if the tail remains until birth, it may indicate that a larger birth defect is present.

Babies born with tails also usually have related neurological defects. A 2008 study also argues that vestigial tails are not benign, but that they could be linked to dysraphism. Science Alert notes that around half of the reviewed cases were linked to spina bifida occulta or meningocele.

Researchers in 1995 also argued that babies born with tails must go through surgery and neuroimaging to ensure that their development is on track.

This shows that babies that are born with tails may require medical attention beyond removal surgery.

Despite these risks, such tails have been reported as if they were harmless and undisputed effects of genetics. This could partially be due to the fact that it is still a mystery if this true tail was directly rooted in the embryonic tail. Science Alert explains that there is not sufficient research to know where the abnormality is.

Nevertheless, regardless of where the tail actually came from, evidence suggests that it resulted from congenital issues.

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