Scope of existing sciences
One might imagine that physics would for example concern itself with all aspects of physical systems, biology with all aspects of biological systems, and so on. But in fact as they are actually practiced most of the traditional sciences are much narrower in scope. Historically what has typically happened is that in each science a certain way of thinking has emerged as the most successful. And then over the course of time, the scope of the science itself has come to be defined to encompass just those issues that this way of thinking is able to address. So when a new phenomenon is observed, a particular science will typically tend to focus on just those aspects of the phenomenon that can be studied by whatever way of thinking has been adopted in that science. And when the phenomenon involves substantial complexity, what has in the past usually happened is that simpler and simpler aspects are investigated until one is found that is simple enough to analyze using the chosen way of thinking.