Do you know why humans don t have long tails?

According to foreign ** reports, scientists at the University of Pennsylvania in the United States recently found that humans do not seem to be suitable for keeping their tails, and the early ancestors of humans lost their tails not more than once, but twice. The scientists' findings, published in the journal Contemporary Biology, could not only explain why humans don't have a tail in tow, but also help to understand why humans have a tailbone, which is a real tail that did grow in the early stages of life, but then gradually disappeared. Lauren Saran, a professor in the Department of Earth and Environmental Sciences at the University of Pennsylvania and the leader of the research project, said, "The earliest vertebrate ancestors of humans always had a fleshy tail.

This tail was also found in the earliest embryos of humans. It's hard to completely ** them without causing other problems. As a result, both fish and humans have had to suppress the growth of this tail, leaving behind a degraded tail that hides in the body.

The earliest origins of this mysterious vestigial tail can be traced back to fish. In his study, Saran analyzed the eggs of a 100-million-year-old fossilized fish of Aetheretmon, the most ancient ancestor of today's land animals. The aetheretmon has a fleshy tail with scales and a flexible tail fin.

Saran found that the two structures were completely independent. By comparing the eggs of the aetheretmon with other existing fish, Saran found that the two "tail" structures first grew together and then slowly began to grow independently.

The discovery overturns a scientifically accepted scientific view for nearly two centuries that the tail fin of modern adult fish is only part of the tail of a common ancestor with land animals. Saran's discovery completely separates the two, meaning that these two tail evolutionary paths are completely different. The fish loses its fleshy tail, but retains that flexible caudal fin for its swimming function.

Saran explains, "Leaving only this tail fin has many evolutionary advantages, while a fleshy tail only brings interference. ”

We can see that many mammals have a long or short tail. Why doesn't the man have a tail?Let's start by looking at the function of the tail, which has many uses for animals.

Some can support their bodies with their tails. Some can use the tail to maintain balance, and some more directly use the tail to repel mosquitoes, according to the theory of evolution, human beings evolved from animals, in the process of evolution, the human brain gradually becomes more and more developed, the action is more and more flexible, many functions that originally need the tail to assist, can be completed without the tail. As a result, the tail loses its meaning of existence.

Slowly, the tail degenerates. This phenomenon is genetically recorded, so that the offspring of the person gradually lose their tails. However, sometimes there are unexpected situations where the fetus has abnormal genes in the early stages of formation and the tail does not degenerate, and the baby may be found to have a tail after birth.

But even then the tail will not be too long. <>

Fish later evolved into semi-aquatic animals, and when they evolved into terrestrial animals, they lost their flexible tail fins. However, the fleshy tail has slowly become the tail of the dogs, cats, cows and other animals that we are familiar with. For dogs, that tail is very useful for visual communication, can also be used to chase away surrounding insects, and of course other functions.

For adult apes, including human ancestors, the tail evolution goes even further. Saran explains, "They even lost their bony tails that they had retained for better upright movement. Like fish, the remains of the bony tail in the embryo are hidden under our backs, forming the tailbone, and do not grow into the body structure of the arms and legs.

As a result, human and fish embryos share a common mechanism to inhibit tail formation. ”<

Tails first evolved 500 million years ago, and they played every role you can imagine. Geckos use their tails to store fat, birds use their tails to control the direction of flight, and rattlesnakes use it to scare off predators. But for most mammals, it has one main function:

Balance. However, when the species evolved closer to humans, the tail disappeared.

Gorillas don't have tails, chimpanzees and apes don't have tails, and of course humans don't have tails. The reason for this has to do with the way we walk. Some of us primates walk on our knees with their chests diagonally to the ground; In addition, like gibbons and humans, they can walk completely upright.

Now, walking this way gives us a huge advantage.

Because unlike quadrupeds, they have to exert effort with every step. The two legs are affected by gravity, which saves us effort, and with each step we take, gravity pulls us forward. As a result, when we walk, we save 25 percent effort than walking on four legs.

In the wild, every strand of effort you save makes the difference between surviving and starving, and this way of walking completely eliminates the need for the presence of the tail. Although a human head weighs a full 5 kilograms, when a human walks, the head is above the body and not in front of it, so there is no need for a tail to balance the body.

However, our primate ancestors still had tails, and if you look at the human spine, you can see that the last few bones are partially glued together, which is the tail vertebrae. That's all we have left for our tail.

In rare cases, babies are born with something like a tail, but that's not a tail. Many times, these tails are tumors, cysts, or even parasitic twins.

More rarely, they are true branches of the spine, but it is completely devoid of bones, it is a hose made of fat and tissue. Usually, this type of tail is a birth defect, a spinal deformity called spina bifida. In these cases, doctors will perform surgery to remove the tail, which is not harmful to the baby.

1. With the development of human evolution, the brain is becoming more and more developed, and the movements are becoming more and more flexible, and the tail loses its original function, which will hinder the movement of human beings, and slowly, the tail degenerates. This phenomenon is inherited, so people don't have tails.

2. Look at these two mechanisms proposed by Darwin from the perspective of modern evolutionary theory. The use of advance and waste should be taken apart: the use of in, that is, the belief that the frequent use of a certain organ by animals can cause this organ to become more and more developed in the offspring, which is the use of acquired inheritance to explain the evolution of adaptation to the environment, which is in conflict with modern evolutionary theory.