Could humans be aliens? How did humans appear on the earth?

Regarding whether human beings are aliens, let's not talk about it for the time being. We can talk first. If there are aliens in the universe, can they really reach the earth?

We often say "space", in fact, space is really empty. The distance between two adjacent star systems is more than 4 light years. For example, the nearest solar system, proxima centauri, is 4.2 light years away. At present, according to the fastest spacecraft, it will take at least 400 years to immigrate to neighboring galaxies. However, with the current level of human technology, we can't immigrate to proxima centauri with food and fresh water for more than 400 years, as well as various means of subsistence necessary for human beings.

Moreover, not all aliens can evolve civilization. There is a simple reason. In the universe, the emergence of civilization is a very low probability thing.

First of all, the birth of civilization must depend on the birth of higher life, which requires living environment. According to the current human research, this planet can give birth to higher life, which requires at least the following conditions:

There is an ozone layer to block ultraviolet rays.

The distance from the stars should not be too close or too far;

The size of a star cannot be too big or too small;

There is liquid water;

There is a global magnetic field that can resist the solar wind;

Conditions, such as protecting a larger planet inside the star system.

Few planets can meet these conditions. Although the universe is almost infinite and there are many planets, the probability of breeding higher life is very low and almost impossible.

Moreover, even if a planet is born with advanced civilization, it must be very far away from the earth. If human beings are aliens, it is impossible for them to reach the earth by spaceship.

In addition, there are high and low levels of civilization. Even if a planet can give birth to advanced life and evolve civilization, if the degree of civilization is similar to that of human prehistoric civilization, then aliens at this time simply can't build a spaceship.

If the civilization of the planet is very high, far exceeding the civilization of human beings, then it is easier for them to directly transform nearby planets than to immigrate to the earth.

So the probability that humans are aliens is so low that it is almost impossible.

human evolution

According to the evidence currently available to paleoanthropologists, human beings are indeed terrestrial creatures and evolved step by step on the earth.

As early as 6,543.8 billion years ago, when dinosaurs ruled the earth, the ancient ancestors of human beings had already lived on the earth, but because the main ecological niche of the earth was occupied by dinosaurs at that time, the ancient ancestors of human beings at that time relied on arboreal and nocturnal ways to drag out an ignoble existence under the eyes of dinosaurs.

About 65 million years ago, an asteroid with a diameter of 10 km hit the earth, and the shock wave generated by the impact caused a large number of dinosaurs to die instantly; A large amount of shock wave energy leads to frequent volcanoes, earthquakes and tsunamis, which disturbs the original order of the earth and makes the earth's environment change dramatically.

In this incident, a large number of vegetation died, and dinosaurs who ate herbivores began to die in large numbers because they could not find enough food. Just like dominoes, carnivores who eat herbivores began to die in large numbers. The whole process lasted tens of thousands or even hundreds of thousands of years.

Although mammals also suffered heavy losses in this incident, they need less energy because of their small size. In addition, mammals will breastfeed their offspring with milk, which will improve the survival rate of offspring. Therefore, mammals were the first to recover from this crisis and gradually occupied the main ecological niche of the earth.

Apes, the ancient ancestors of human beings, occupied a niche in trees and lived by collecting fruits and young leaves. However, the good times did not last long. In Africa, which originally belonged to forests, the climate gradually became dry and rainy, and the virgin forests gradually faded, replaced by savanna characteristics.

At this time, the African Rift Valley has been formed, and apes living in eastern Africa can't cross the African Rift Valley to find other forests, so some apes are forced to live in the fields. In this process, humans can gradually walk upright, and the energy consumed by walking upright is 1/3 of that consumed by walking on all limbs.

Another thing that humans do after going to the fields is to start eating meat. Although we ate carrion at first, the energy in meat is much higher than that in plants. It is understood that the heat of a fish seed is equivalent to 25 berries.

Because humans began to eat meat, and meat does not need a long intestine to digest, so the human intestine has also become shorter, and the shortening of the intestine has also saved some energy.

At this time, human beings have a lot of extra energy, which is used by human beings to develop their brains (in short, human beings can't choose the direction of evolution, so they are described for convenience of expression). With the increase of brain capacity, human beings have the ability of thinking and abstract thinking, so human civilization was born.

Although according to the research of paleoanthropologists, the complete evolutionary chain of human beings has not been completely found, there is enough evidence to show that human beings are indeed life on earth, not the earth crossed by aliens.