George is studying Basque, a language spoken by a group of people who live in the Pyrenees mountain range between France and Spain's. He's studying the history of his language to determine how it is complex grammar evolved from other languages. To which school of thought does George most likely belong to

He belong to the school "Cultural History".

This discipline studies the behaviors and characteristics of determined humans and societies in the past, along with its historical context and its correlation to the present with the purpose to record, interpret, describe, and understand past matters and its correlation to some specific characteristic of the present. The language is one of the factors that may be studied, and it's usually studied to understand and determine its evolution to a present language, just as George intends to do.