Modern humans are experiencing synchronous declines in metabolic, cognitive, emotional, physical, reproductive, and adaptive capabilities across every major medical department. Existing frameworks—evolutionary mismatch, allostatic load, developmental origins, and environmental toxicology—explain fragments of this pattern but do not account for its universality, acceleration, or cross-kingdom parallels. The Resilience Deficit Theory (RDT) proposes that these trends arise from a single upstream process: the sustained removal of ancestral oscillations that once maintained Adaptive Capital across the lifespan. RDT identifies four core causal mechanisms that operate across biological levels:(1) Cycle Removal (loss of circadian, metabolic, seasonal, microbial, physical, and social oscillations),(2) Metabolic Overload (continuous caloric availability, inflammatory signaling, hormonal flattening),(3) Neuro-Cognitive Hyperstimulation (digital reward excess, attentional fragmentation, sleep disruption), and(4) Intergenerational Drift (erosion of kinship scaffolding, caregiving apprenticeship, and early-life regulatory buffering). These mechanisms produce a six-domain phenotype—the universal decline of metabolic, cognitive, emotional, physical, reproductive, and adaptive capacities—observed independently in 23 clinical departments, from cardiology and endocrinology to pediatrics, geriatrics, psychiatry, oncology, and reproductive medicine. Each department’s longitudinal data reveal consistent, directionally aligned, multi-decadal declines even after accounting for toxins, pollutants, and socioeconomic factors. Beyond humans, RDT is supported by cross-kingdom and cross-species evidence: domesticated plants, captive mammals, companion animals, and the human microbiome exhibit similar resilience erosion under modern-like conditions characterized by reduced variation and continuous abundance. Historical analyses of late-stage civilizations further reveal the same signature pattern—early metabolic and reproductive decline, emotional instability, and reduced physical robustness—during periods of excessive comfort and flattened environmental rhythms. Together, these findings position RDT as a unified systems framework explaining why resilience is diminishing across modern populations despite unprecedented medical advances. The Mandalam Edition integrates clinical, biological, ecological, historical, and cross-kingdom evidence into a single architecture, offering a testable model of how restoring oscillatory inputs—circadian, metabolic, microbial, physical, and social—may rebuild human Adaptive Capital in the decades ahead.