![]() ![]() They compared genetic data from six species of hominoids and nine species of monkeys, looking for differences that could be linked to the presence or absence of tails. Related: Tale of 2 tails: Why do sharks and whales swim so differently? But tail loss is thought to have originated even earlier: about 25 million years ago, when the hominoid lineage of humans and apes diverged from Old World monkeys, Xia and his co-authors wrote in the study. The earliest known tailless ancestor of humans and apes is a primate genus called Proconsul, which lived in Africa during the Miocene epoch (23 million to 5.3 million years ago) and had no sign of caudal vertebrae - the bones found in tails. Following a recent tailbone injury, Xia decided to investigate the seat of the problem more closely, to learn how evolution had stripped humans and apes of their tails. "I wondered about it when I was a young kid, seeing almost all kinds of animals have a tail - but not me," Xia said. Like humans, chimpanzees - one of our closest living relatives - are tailless. He is also the lead author of a new study identifying a genetic "smoking gun" for how humans lost their tails the findings were published September 2021 on the preprint server bioRxiv and have not been peer reviewed. Xia is researching the genetic mechanisms of human development, disease and evolution. Skin-covered pseudo tails contain muscle, nerves, blood vessels and connective tissue, but they lack bones and cartilage and are not connected to the spinal cord, as true tails would be.īut how did humans become tailless? For Bo Xia, a doctoral candidate at New York University's (NYU) Grossman School of Medicine, that conundrum has been a source of fascination since childhood, he told Live Science in an email. These vestigial protrusions are embryonic leftovers and are usually pseudo tails rather than "true tails," according to a study published in 2012 in the Journal of Indian Association of Pediatric Surgeons. Sometimes human babies are born with tails, though this is exceptionally rare. What kind of tissue is present in a human tail? “The real ones represent the persistence of a remnant of the embryonic tail formed between the fourth and eighth week of gestation, being composed of adipose and connective tissue, blood vessels, muscle and nerve fibers,” the researchers explained.After that, the only remnant of these lost tails in humans is about three or four vertebrae that form the coccyx, or tailbone. The researchers did not obtain permission to review the case file. Due to the common ectodermal origin between the skin and the central nervous system, it is essential that the pediatrician or pediatric surgeon investigate the presence of hidden spinal dysraphism in patients with suspected skin lesions, as they may be the only visible abnormality and early diagnosis can prevent evolution to severe neurological changes,” the article explains. “The presence of a true human tail in neonates is a rare congenital anomaly and should be investigated through physical and radiological examinations in a comprehensive manner. “Treatment for human tails should be done with surgical resection of the appendix, based on clinical and radiological examinations, especially the study of MRI,” it says. They have been reported since the end of the 19th century, being generally small in size and located around the midline and lumbosacral region,” the article reports. “Lumbosacral appendages, or human tails, are rare entities and represent the remnant of an embryonic vestige. These lumbosacral skin appendages are often associated with hidden spinal dysraphism and other malformations such as lipoma and anchored cord syndrome.”īe forewarned that the tail photos are graphics and may disturb some. The article explains, “Human tails are rare congenital anomalies and describe protrusions located around the midline of the lumbosacral region covered by skin, representing an embryonic trace. The headline in the March, 2021, article read, “A true human tail in neonate.” The article was first published in the Journal of Pediatric Surgery Case Reports. The report came from a journal article in Science Direct, which published photos of the baby’s tail. You can see some of the photos in this article, but be aware that some might find them disturbing. Photos of the human tail were published in a journal article. Photos of the Brazilian baby born with a tailĪ Brazilian baby was born with a tail. Journal of Pediatric Surgery Case Reports ![]()
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