Basque mythology survives only as legend recorded from rural informants after Christianization was already dominant, and Basque, a language isolate, offers no comparative linguistic route to an earlier stage the way related Indo-European mythologies do. Nothing currently ties the figure of Mari or the wider nature-spirit cast to any datable period before the ethnographic record itself.
What would resolve this An inscription, cult site or artifact in the western Pyrenees securely tied to a named pre-Christian Basque deity or practice, or a linguistic reconstruction anchoring core mythological vocabulary to a datable stage of the Basque language, would give scholars an actual point to reason from instead of the modern record alone.
Openarchaeology and historical linguisticsJose Miguel de Barandiaran, ed. Jesus Altuna, trans. Frederick H. Fornoff, Linda White and Carys Evans-Corrales, Selected Writings of Jose Miguel de Barandiaran: Basque Prehistory and Ethnography