The mediocrity, also known as the Copernican principle, states that since life originated on Earth, a similar process is likely to happen or already happened elsewhere in the cosmos, where the same molecules exist and the same laws of physics probably apply.
This idea was reinforced by Edwin Hubble’s discovery that the universe is substantially larger than humans first thought. Earth is a landa planet in a typical planetary system, located in an unexceptional region of a common barred-spiral galaxy. Frank Drake and Carl Sagan have been the main supporters of this theory.
The mediocrity principle also applies to humanity since recent discoveries suggests that all humans have a common ancestor about 100,000 years ago, and that they share a common ancestor with chimpanzees and bonobos about six million years ago.
In his book, COSMOS, Dr. Sagan indicates that there are about Ten Million (10,000,000) of such technologically advanced civilizations in our galaxy.