Diseases of the past were not our diseases: Rethinking retrospective diagnosis in medicine

Retrospective diagnosis of past individuals is inherently complex and often misleading. Although ancient pathogens can now be identified with molecular tools, their clinical expressions differed markedly from those observed today. Physiology, immunity, microbiota, and human-environment interactions have changed profoundly over time, altering disease behavior and outcomes. Diseases should therefore be understood as evolving processes shaped by long-term host-pathogen co-evolution rather than fixed entities. Reconstructed ancient microbiota reveal dramatic ecological shifts driven by diet, hygiene, industrialization, antibiotics, and climate. Identical pathogens could thus produce different diseases in different historical periods, complicating paleopathological interpretation. Recent case studies illustrate infections that were once common but are now rare, displaced, or clinically transformed. Ignoring paleoecology and semantic shifts in medical terminology leads to biased and anachronistic diagnoses. The article calls for methodological humility and "context-first" approaches instead of projecting modern disease categories onto the past. This evolutionary perspective not only refines interpretations of ancient remains but also encourages more flexible, personalized, and reflective modern medical practice.