The earth was born 4.55 billion years ago, while humans have been on the planet for only a few million years. This huge discrepancy begs the question of whether other intelligent beings could have existed on earth before humans appeared.

Since this is a reasonable hypothesis, a number of people have held a keen interest in it, and from time to time in the past, people have claimed to have found things on earth that should not have existed hundreds of millions of years ago - products of prehistoric intelligence.

These discoveries are as diverse as 300 million-year-old 'screws', 400 million-year-old 'gears', 500 million-year-old 'footprints' on trilobite fossils, and even 2 million-year-old 'nuclear reactions'. There are even 2 billion year old 'nuclear reactors'.

However, all these so-called products of prehistoric intelligence have been dismissed by rigorous scientists, and in fact the so-called "Screws" And "Gears" Are actually fossils of sea lilies, and the "Prehistoric footprints the so-called "Screws" And "Gears" Are actually fossils of sea lilies, the "Prehistoric footprints" Were formed by accidental spalling of hard parts of rock, and the two-billion-year-old "Nuclear reactor" Was formed naturally in a specific environment.

Of course, the fact that we cannot find prehistoric products of intelligence does not prove that there were no other intelligent beings on the earth before humans appeared, after all, our knowledge of the earth is still very limited, and perhaps they existed in areas that are now beyond our reach. So let's discuss if scientists have discovered something that shouldn't have existed hundreds of millions of years ago, should humans be wary?

If this is the case, it will completely eliminate the loneliness of human beings in the universe, and also satisfy their curiosity, and human beings may even learn advanced science and technology from prehistoric intelligent products, which seems to be good news in this respect, but if we think about it more carefully, we will find that for human beings, the discovery of prehistoric intelligent products hundreds of millions of years ago is actually bad news, and human beings must be wary.

Why do we say this?

First of all we need to consider the question, where have these intelligent beings gone now? There are two possibilities as to where these intelligent beings came from hundreds of millions of years ago: One is that they were intelligent beings from an alien planet, often referred to as aliens, and the other is that they were "Native" Prehistoric civilisations on earth.

If they were extraterrestrials, this is quite explainable, as they could have come to earth as a 'tourist', stayed for a while and then left the planet. If this were the case, it would mean that intelligent civilisations capable of interstellar flight existed in the universe hundreds of millions of years ago.

Theoretically speaking, after a civilization has developed into one that can cross the stars, there is basically no risk of extinction. It is conceivable that if their civilization has developed until now, their technology is absolutely beyond human imagination, and when they come to earth again, human strength will not be able to compete with them at all, and what awaits humanity will be an unpredictable fate.

So would it be better if they were a prehistoric civilisation 'born and bred' on earth? No, in fact, it could be worse news.

One more possibility for prehistoric civilisations, as opposed to aliens, is that they are already extinct. Earth's natural environment has not always been very kind to life, and as far as we know, there have been at least five biological mass extinction events on the planet, and any one of them would be difficult for humans to survive if it happened now.

It is easy to imagine that at some point in the future, the earth's natural environment may change dramatically, and if humans have not developed sufficient technology by then, it will be difficult to escape. Generally speaking, mankind has not given much thought to this kind of problem, but if mankind does discover an extinct prehistoric civilisation, it will have to be alerted.

Of course, one could argue that prehistoric civilizations were highly technologically advanced and have now long since left the solar system, but the point is that since prehistoric civilizations had the ability to leave the solar system, they are just like the aliens we discussed earlier, and after hundreds of millions of years of development, they can now return to earth whenever they wish.

But there is another question: Why did they all leave the solar system? For humans, even if they become an interstellar-capable civilisation in the future, it is unlikely that all of them will leave the solar system, unless there is an imminent cataclysmic change in the solar system (which could be natural or man-made) and humans have to evacuate all of them.

This could also be the reason why prehistoric civilizations all left the solar system. Imagine that since such a thing has happened before, it could happen in the future, and judging from the current progress of human technological development, it would be impossible for humans to all leave the earth for a long time to come, that is, in the case of an imminent giant change in the solar system, a technologically powerful prehistoric civilization would be able to leave the earth comfortably, whereas if humans are not technologically powerful by that time, it will be very difficult to escape.

It may seem fascinating that "Scientists have found something that shouldn't have existed hundreds of millions of years ago", but this is actually bad news for mankind, so it's probably best to say that we have not been able to find prehistoric intelligence on our quest.