The Carden reindeer femur is especially thought-provoking because its possible stone-tool mark may record a brief human encounter without demonstrating occupation. Castlepook’s mixed, long-lived deposits make taphonomic interpretation crucial: the bone could reflect processing, yet cannot reveal whether the animal was hunted, scavenged, or encountered during a temporary crossing. This uncertainty contrasts sharply with Ireland’s later, better-established Mesolithic evidence and emphasises how environmental corridors differed for animals and people. Comparing Castlepook with contemporary north-west European sites might clarify what fleeting visits leave behind. What evidence would most persuasively indicate recurring human movement through Ice-Age Ireland rather than a single visit?