The Mayan civilization clearly recorded the four prehistoric civilizations before it. Which generation of civilization can humans be considered?

This is uncertain because it is impossible to tell how many or whether there were other civilizations before humans.

First of all, basements made of reinforced concrete are easier to store than fossils. Not to mention various mines, wells, subways, and even various air raid shelters, shelters, and silos. They may be destroyed, Collapsed and buried, but the materials of which they were composed were not left untouched, but remained in the strata and became very unique and distinct fossils.

Concrete itself is equivalent to artificial rock, and it is not difficult to preserve compared with ordinary rocks. Inorganic non-metallic materials such as glass, artificial crystals, and ceramics are also quite stable and have high hardness, which is beneficial to preservation. Some other materials, such as metals, are difficult to store in their free state, but they still leave traces when they become compounds. Even organic matter doesn't always break down easily. Amber, for example, can be stored for nearly 100 million years. Modern organic compounds do not disappear easily.

Secondly, even if building materials disappear, they cannot be restored to their original form. In other words, each formation is non-renewable and any damage to them is irreversible. Countless creatures have left fossilized traces and can leave wormholes as small as the end of a finger. There is no reason why traces of drilling around the world cannot be preserved.

Not to mention geochemistry, pollution emissions caused by activities have spread all over the world. Changes in the abundance of radioactive isotopes caused by nuclear reactions. Activities cause large amounts of matter to deviate from natural levels. These are difficult to destroy before destroying the Earth.

Therefore, there is actually a civilization that preceded humans, but the possibility of finding no trace is infinitely close to zero.