The actual reason is to integrate the barren element particles in the cosmic system far beyond the solar system with the genes generated by the colorful universe derived from the rich civilization, far beyond the barren elements. From another perspective, it is to cram the knowledge far beyond the solar universe into this universe as much as possible through screening and simplification. This is like confining the human brain, heart, blood vessels, liver, and all other useful and important organs to a mere human body - and this body, to the greatest extent, can barely accept it.
So, why not put all these organs in a bigger container? The answer is simple, because circumstances don't allow it.
The solar system universe is too barren, in the combination of planetary environment creation, higher civilizations have tried to integrate their own civilization genes and environmental elements on many different planets, to maximize the continuation of their own civilization and race. Unfortunately, the stranded mother ship did not have enough material and energy to support the creation, the mother ship did not have such a huge energy to support, and finally, after evaluation, only in the solar system of planets, select a part of the planet for the test. Through a large number of simulation calculations and the experimental creation of small sizes of different planets and galaxies, the last choice is to choose a relatively suitable star to carry out the propagation of civilization, and this star is the Earth.
The choice of Earth is only one of the best of the original multiple test choices, in fact, in the current solar system has been known to nine planets, have tried this environmental modification and genetic match creation experiment.
According to the environment of the nine planets, the protoss civilization initially tried to transform and create the original elements with the elements of the planet, and found that the planets that were more consistent were only Mars and Earth. The time of the experiment and creation of the two planets is basically the same, and for the Protoss, the relative same time may be only a few hundred thousand years apart, and humans cannot use their own defined time to compare with the Protoss time.
In the end, the Mars experiment failed, the Earth experiment barely succeeded -- why Mars failed, we'll explain later; The failure of the Mars experiment led to the emergence of the Moon.
Back to the creation of man.
The scientific research of human beings has found that the emergence of human beings has experienced a very long time, about 5 billion years or so - this is based on the cognitive view of human beings. At present, human beings can roughly estimate that the record of human activities is about 10,000 years or so. In some respects, the time of human existence in the civilization inheritance on Earth can basically be ignored. However, this 5 billion years is the time to create the environment in which humans emerged, or this cycle is a very long time from the perspective of advanced civilizations, even if they have almost eternal life, it is a long process.
Although Mars and Earth are more suitable, the higher civilization still understands that the eggs should not be put in the same basket, and that for the two native environments of Earth and Mars, it is just possible to apply uniform genes and elements to the two planets to observe the development of both - since it is an experiment, so long as one succeeds, and the other, If you fail, just give up.
Thus, the transformation of the two planets began...