Clinical psychology requires continuous research to encourage integrative explanations for the complexity of mental disorders and their underlying causes. Biological evolutionary approaches have shown particular heuristic power for this endeavor. Life history theory (LHT) is an evolutionary model that incorporates novel and significant theoretical and empirical advances. However, there is a growing need for the incorporation of other successful evolutionary approaches. Thus, the goal of the present paper is to propose potential integrative connections between evolutionary causal modes, behavior systems, and LHT. For this, borderline personality disorder is used as an example of a condition that can be understood as an interaction between stress and attachment psychobiological systems (proximate causes), within the framework of ultimate causes clarified by LHT. To conclude, we will outline several aspects that could enhance the clinical field with implications for assessment and intervention.