The occurrence of complexity study is a historic "sign," symbolizing that some functionalist biologists have admitted that the functional experimental system has reached its limit and cannot reach the original goal of reductionist biology in term of life-component assemblage.
The "complexity" is a problem, which makes the benevolent see benevolence and the wise see wisdom. The neoadaptationists prefer to use the term deep structure to name it, a concept more accurate and essential than the term complexity. The reason is that the objective modulation structure and mechanism mode can be simplified to comparative relationships, such as subfunctional processes' order, priority, and so on. For diversity biology, these relationships can be understood as the higher-level organizations give specific meaning to the subfunctional processes; and the components must be involved in a start-up combination with different outcomes and at different times, in the interest of the whole. Therefore, the regulatory mechanism is essentially a problem of deep structure. There are regulatory mechanism problems at any biological level.
Neoadaptationism recognizes that complexity is elicited by deep structures. Complexity is the phenomenon of deep structure, and deep structure is the essence of complexity. You can say that life phenomenon is complex, but this does not mean it cannot be reduced. From the perspective of neoadaptationism, life meaning phenomenon is complex and can be reduced. The method is the new comparison experimental system based on the vitastate.
Because any kind of functional meaning can only be identified through comparative study, and despite at any level, the functional meaning would have no way out without comparative study. The route-tracking method cannot help researchers find the priority of the courses, or determine which are important or unimportant, pressing or otherwise, similar or dissimilar. Certainly, the method is not able to identify the initial causal relation (a meaning relation) between a detailed process and another one. So, when you go along the route to explore, you will find that functional paths may be intercrossed, repeated, looped, bifurcated, compounded, and circulated. Eventually, route tracking may reach an impasse due to route explosion.
In other words, without comparison, we cannot distinguish various vitastate relationships in the route web. When we use an evolutionary system to make the comparisons, the system is equivalent to a reference, which can help identify vitastates' priority, importance, and so on. The conventional method of functionalism is to solve the process details of modulation through route tracking. When the route tracking creates information explosion and produces uncertain outcomes of experiments, functionalism comes to a dead end. In fact, this is the cause of complexity.