When humans and apes are put together, it's easy to see that they have an extra organ – their tails. Many animals have tails, and the tail plays an important role, the tail is the "accelerator" of fish, the "weather vane" of birds, or the "balance bar" of apes. However, why did human beings lose this important organ along the way? If humans had tails, what would we do with them?
When did humans lose their tails?
According to the current consensus, humans and apes are close relatives, and we evolved from a common primate ancestor, so what "went wrong" in the middle so that the offspring of the same root and origin are divided into tailed and tailless?
Researchers at New York University in the United States compared the DNA of six species of tailed apes with that of nine species of tailed monkeys and found that there was a genetic mutation in the tailed pie, while the tailless pie did not have this change. The mutation affected a gene called TBXT, and to verify that this gene mutation is related to the loss of the tail in humans, the researchers conducted experiments on mice. Some of the genetically modified mice did not develop tails, and some did have tails, which were much shorter than normal mice. Therefore, it can be said that the mutation of the TBXT gene is indeed an important factor in determining tail development.
However, TBXT mutations are not the only reason humans lose their tails. In experiments, the mice that developed short tails tended to have uneven tail lengths, but there was very little difference in tail vertebrae between us. So, there must be other genetic mutations involved that allow us to produce such a uniform body structure.
The known apes that have lost their tails can be traced back to 20 million years ago, the proto-Conshure ape. Scientists speculate that about 20 million years ago, a protoconsul ape was born with this gene mutation and passed it on to its offspring through breeding. Later, due to natural disasters, the koala had to leave the trees and walk on the ground. After arriving in the grassland, the tailless ape no longer needs its tail to grasp branches, and it also saves the energy needed to maintain its tail, and is able to walk faster; And when being chased by a beast, there is also a missing "handle" that is caught, so the lack of a tail becomes an advantage. So this gene was passed down from generation to generation until it was passed on to humans who walked upright, so that humans lost their tails from the beginning of their birth.
Do you want a tail?
Losing the tail still poses a certain risk to humans. Experiments have found that the TBXT mutation not only shortens the tail of mice, but some mice also develop spinal deformities similar to human spina bifida. Researchers speculate that the relatively high incidence of spina bifida in humans may be a sequelae of tail loss.
In this way, can humans still recover their long-lost tails? It's not easy, and if humans are to grow tails, they have to make big changes not only to genetically modify, but also to make big changes to the body.
The tail is not just an extension that hangs from the end of the spine, it needs the bones, ligaments and muscles around the hip to help hold it in place, and the nervous system needs to be involved in sensing and pulling, just as the movement of the arm requires many tissues to work together. So if humans have tails, there are certain parts of our bodies that have to be adjusted. We need stronger pelvic muscles to support those extra muscles and bones, and longer vertebrae and tail vertebrae are needed to help tail muscles attach. However, these adjustments not only affect balance when walking upright, but also affect gastrointestinal movements and may even lead to incontinence.
We have become accustomed to walking without a tail, and if we suddenly have an extra tail, we will lose our balance due to the uneven weight of the front and back. On the other hand, the bones and muscles saved because of the absence of a tail compensate in people's front and back. A stronger back is better able to withstand the impact of a fall or jump, while the muscles in the abdomen provide support for our abdominal organs, such as the bladder and bowel, allowing the digestive tract to withstand more pressure and maintain normal digestive activity during walking and running, ensuring that we don't lose our excrement. Therefore, if we want to grow a tail, we will have to take a long time to adapt to these changes.
However, although it is very troublesome to grow a tail again, scientists have a way to get an extra tail without changing our body, and that is to install a mechanical tail. In 2019, scientists at Keio University in Japan developed a wearable tail that can be worn on the back and manipulated as you please. The tail is made to mimic the bones of a seahorse's tail, and the body is made up of several joints that are connected to each other, and the number and weight of the joints can be adjusted to match different users, and the joints have four built-in pneumatic artificial muscle actuators that allow the "tail" to move in eight directions.
What can you do with a tail?
Japanese scientists didn't just develop the mechanical tail for curiosity, it was endowed with some important functions.
The tails of most vertebrates have a wide range of applications, such as maintaining balance when moving, sensing their surroundings, and even signaling and communicating through the movement of their tails. Scientists hope that this mechanical tail will also fulfill these functions. The mechanical tail has a built-in analysis device that can guess the center of gravity through the body's movements and position, and then send signals to respond accordingly: if the body leans forward, then the tail will be cocked; If tilted horizontally, the tail will be tilted upwards in the opposite direction to maintain the user's balance. For people with leg problems or heavy loads, the ability to maintain balance can be of great help. In addition to helping people stand firm, the mechanical tail can also simulate situations through force feedback and haptics, such as the feeling of being blown by strong winds. In the future, this technology may be used to help patients with sensory loss due to trauma or illness to recover.
Of course, for most people, these functions are a bit frivolous, and it is more convenient to have no tail. But if humans never lose their tails, what changes will the tail bring to us?
After a long period of evolution, the tail of modern Homo sapiens may become very flexible, just like a monkey can use its tail to pick up objects, we can also use our tail to grasp things, we can use our tail to pull out the key when our hands are occupied by shopping bags, and we can also use our tail to grasp the phone to read messages when we are holding a rice bowl in both hands. The tail may give us good balance, the acrobat can perform without a stick, and the balance beam player will be able to perform more complex movements.
The tail may also have an important place in the social sphere. The beauty of the tail will become one of the criteria for choosing a mate, and the service items of the beauty salon may add tail beauty, and the hand-holding between boyfriends and girlfriends may become tail pulling, and the tail may be hit instead of high-fives to express encouragement or joy. Even, people will design a set of social etiquette for the tail, such as the tail facing down when talking to the elders, not flicking the tail in public, and not exposing the tail on certain occasions. All in all, if the tail is never lost, it is likely to become an important organ in humans.
But then again, if our ancestors had kept their tails, would we have followed the evolutionary path of walking upright and become what we are today? All of this may never be answered, but there is no need to bother to find an answer, because the loss of the tail itself is the perfect answer given by evolution.