Jakarta, CNN Indonesia —
Man grows tailless from birth. At the same time, modern primates like monkey and the lemurs still have it. Why is that?
Tail loss is thought to be part of the backdrop for humans evolving to be bipedal (walking on two legs), but exactly how we lost tails is a question scientists have long sought.
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Collect Live Science, researchers found genetic clues to why humans don’t have tails. They identified a so-called jump gene that is linked to tail growth. This gene probably jumped to another location in the genome (a collection of DNA) of primate species millions of years ago.
This gene creates a mutation that removes the long tail in modern humans. However, humans actually still have tails when they are embryonic. During the formation of the fetus, the tail slowly disappears and widens into the human spine.
The loss of the tail from the embryo occurs in the eighth week phase through a process known as apoptosis, a type of programmed cell death that is built into the development of multicellular life.
After that, the only remnant of this missing tail in humans is the vertebrae that make up the coccyx.
Sometimes, human babies are born with a tail, although this is very rare. This vestigial (remnant) protrusion is the remnant of the embryo and is usually a pseudotail.
False tails covered in skin contain muscles, nerves, blood vessels and connective tissue, but they lack bone and cartilage, and are not connected to the spinal cord like true tails are.
Doctoral candidate at New York University’s (NYU) Grossman School of Medicine, Bo Xia admits to “wondering about it when I was a kid, seeing [bahwa] almost all kinds of animals have tails, but I don’t.”
Xia is currently researching the genetic mechanisms of human development, disease, and evolution. He is also the lead author of a new genetically identified study of how humans lost their tails.
The earliest known common ancestor of humans and tailless apes is a primate genus called Proconsul, which lived in Africa during the Miocene epoch (23 million to 5.3 million years ago) and has no signs of a tailbone.
However, the loss of the tail is thought to have occurred earlier, around 25 million years ago when the hominoid (great ape) lineage of humans and apes diverged from that of earlier monkeys.
They compared genetic data from six hominoid species and nine monkey species and looked for differences that could be attributed to the presence or absence of a tail.
Experts then suspected the suspect was a short piece of DNA called the Alu element stored in the TBXT gene that regulates tail development.
The Alu element is a type of DNA that can jump from one place in the genome to another, which then affects protein production. This mutation is present in the genomes of apes and humans, but not in monkeys.
The function of the tail and the possibility of its growth in humans on the next page…
Tail Function and Possible Growth in Humans
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