What is the reason for the absence of tails in humans?

What is the reason for the absence of tails in humans?

Approximately 25 million years ago, tailless apes emerged when their ancestors genetically diverged from Old World monkeys in Africa. Rather than having a tail, they retained several vertebrae that eventually fused to form the coccyx or tail bone as evolution progressed. The genetic changes that specifically led to the disappearance of the tail had not been clear until recently.

Doctoral student Bo Shiah (Xia) and his colleagues at New York University’s laboratory conducted research to identify the genetic change responsible for the loss of the tail in hominoids. Their study, published in the journal Nature, focused on a gene known as TBXT. They discovered an additional transposon sequence in the sixth intron of the gene in all hominoids, but not in tailed monkeys.

Experiments revealed that the transposon created a loop that caused the exon to be skipped, resulting in the production of shorter proteins associated with tail loss. Subsequent studies in genetically modified mice confirmed that the transposon sequences were linked to tail loss. The researchers demonstrated that the timing and quantity of protein production were crucial for proper spine development during pregnancy.

However, some questions remain unanswered, and more research is needed to fully understand the evolutionary pressures that led to the disappearance of the tail in hominoids. Evolutionary biologist Terence Capellini from Harvard University suggests further investigations using transgenic mice to explore the sequence of genetic changes that resulted in tail loss.

The study provides valuable insights into the genetic mechanisms underlying the loss of the tail in hominoids and sheds light on the evolutionary processes that shaped this characteristic in ancient apes. Further research may uncover additional genetic changes involved in the evolution of taillessness in primates.

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