Intelligent Design (brief overview).

[I_am_not_mafia]

Of course, you can always take about a more simple version of that system evolving to more complex version of that system.....

But the very first time the system rose, is it possible to go the route of gradual changes? That's the question.

I've realized there is many complex systems that this is not possible.

The problem is that you cannot just extrapolate backwards from a complex system to a simpler version of it. That rarely ever happens. The earlier version is likely to have been radically different. It might not even have been any less complex.

It's also not just the system that you have to take into account, but it's environment and what it has to do to persist in that environment. This makes extrapolating backwards even more difficult.

When there is a new addition or change to a system, the rest of the system can come to depend on it. Take away that change and the rest of the system may collapse.

Classic example adding an invasive species to a new ecosystem.

Simple. No irreducible complexity required.