However, a new theory is emerging that suggests that the opposite may be true. This theory, known as the "outside-in" hypothesis, proposes that complex life evolved first and then, through a process of simplification, these complex life forms gave rise to the simpler cells that we see today.
There is some evidence to support the outside-in hypothesis. For example, some scientists have found that the earliest fossils of complex life forms, such as stromatolites, are older than the earliest fossils of simple cells, such as bacteria. This suggests that complex life may have evolved first and then simplified over time.
Another piece of evidence that supports the outside-in hypothesis is the fact that some of the simplest cells today, such as bacteria and archaea, contain genes that are similar to genes that are found in complex organisms. This suggests that bacteria and archaea may have evolved from more complex ancestors.
The outside-in hypothesis is still a controversial theory, but it is gaining support from some scientists. If this theory is correct, it could revolutionize our understanding of how life evolved on Earth.
