Although some linguists deny the plausibility of the Basque substrate theory, it is widely assumed that Basque, the "Circumpyrenean" language (as put by Basque linguist Alfonso Irigoyen and defended by Koldo Mitxelena, 1982), is the underlying language spreading around the Pyrenees onto the banks of the Garonne River, maybe as far east as the Mediterranean in Roman times ("niska" cited by Joan Coromines as the name of each nymph taking care of the Roman spa "Arles de Tech" in Roussillon, etc.). Basque gradually eroded across Gascony in the High Middle Ages (Basques from the Val d'Aran cited still circa 1000), with vulgar Latin and Basque interacting and mingling, but eventually with the former replacing the latter north of the east and middle Pyrenees and developing into Gascon.