Amal Alachkar

My presentation reframes L-3,4-dihydroxyphenylalanine (DOPA) not as a passive precursor for dopamine, but as a fundamental evolutionary scaffold. I trace its journey from its plausible origins in prebiotic chemistry, arguing that the core physicochemical properties of its aromatic catechol group—redox activity, metal chelation, and polymerization—were essential for the emergence of life. These properties enabled primitive catalysis, photoprotection via melanin-like polymers, and the formation of functional compartments. I demonstrate how this chemical repertoire was repeatedly repurposed by life to solve recurring challenges: for survival (e.g., microbial siderophores, melanin), colonization (e.g., mussel bioadhesives), and communication (e.g., plant allelopathy and the animal neurotransmitter, dopamine). Synthesizing this history reveals a conserved ‘Stress-Motivation-Action’ arc, linking DOPA’s chemistry from passive environmental buffering to the emergence of active, goal-directed behavior. Finally, I propose this evolutionary trajectory culminates in the human brain. Here, DOPA's ancient, non-canonical chemistries—adhesion, chelation, and polymerization into the semiconducting biopolymer neuromelanin—form a multiscale biophysical scaffold. I argue this scaffold provides the structural and electrochemical stability necessary for the canonical dopamine system to operate in a low-noise environment. This stable substrate enables the complex computations that underlie not just motor control, but the subjective experience of cognitive agency. This model thus bridges molecular biophysics with cognition, reframing agency as a phenomenon embedded in the material architecture of life’s earliest survival strategies.