Long before we find the right words for danger, our bodies are already speaking a primitive language of survival. Wisman and Shira’s work suggests that putrescine, released as the body begins to break down, acts as an invisible siren. We don’t smell it and think “death,” yet our pulse quickens, our muscles tense, and an urge to move away takes over, echoing the instinctive flight of animals sensing a predator nearby.

This hidden system doesn’t just apply to decay. Human behavior is quietly shaped by countless invisible signals: the comforting scent of a loved one, the subtle pull of sex pheromones, the unease in a hospital corridor. We like to believe we are purely rational, but under the surface, an older intelligence still guards us. It warns, it repels, it draws us close—or pushes us away—from what our conscious mind has not yet dared to see.