Castlepook Cave highlights the challenge of distinguishing a momentary human encounter from a long, mixed accumulation of animal remains. The marked reindeer femur is intriguing because it may preserve evidence of fresh-bone processing, yet the cave’s disturbed, time-depth deposits cannot demonstrate settlement or even a particular journey. This restraint usefully contrasts with richer Upper Palaeolithic records elsewhere in northern Europe, where tools and hearths contextualise human activity. The cave fauna also reveals an ecosystem shaped by climatic instability and movement. What evidence or comparative approaches would help assess whether the Castlepook mark reflects human activity rather than a natural process?