The cheeky ape hypothesis: Is rosacea the evolutionary price of human buccal fat?

Rosacea is a common, chronic inflammatory skin condition primarily affecting the human face. Clinical manifestations range from mild erythema to disfiguring phymatous changes, such as rhinophyma. Despite extensive research, its primary etiology remains unclear. Current evidence suggests that the disease may begin with an initial vascular insult, which then triggers an inflammatory cascade modulated by genetic, environmental, and microbial factors. However, the mechanisms underlying this initial vascular dysfunction have yet to be elucidated. We propose the “Cheeky Ape Hypothesis,” which offers a novel evolutionary and anatomical potential contributor to the pathophysiology of rosacea. This hypothesis posits that impaired venous return within the facial vein and its tributaries—resulting from bilateral venous compression within the buccal fat pad, a uniquely human anatomical feature—could play a contributory role in initiating of the disease. As deep buccal fat is specific to humans, this anatomical specialization may represent an evolutionary trade-off, which could partly help explain the distinctive prevalence of rosacea in humans. The hypothesis suggests that the interplay between facial venous flow and adipose tissue distribution underpins the pathogenesis of rosacea. Rigorous experimental and clinical studies will be required to investigate and validate the proposed mechanism.