I am wondering if there is any evidence of personality traits like intro versus extroversion existing in native people without any contact with modern society, or if they are a result of modern life.
See the study below conducted on Tsimane (indigenous Bolivians). It uses Big-5 traits to assess whether if a general factor of personality can be identified with the natives (who mostly fit your criteria) similar to western population studies.
Which is 'evidence' that personality traits exists in indigenous tribes the same way they do in Western populations, since well, how else would they measure it?
van der Linden, Dimitri et al. “How Universal Is the General Factor of Personality? An Analysis of the Big Five in Forager Farmers of the Bolivian Amazon.” Journal of cross-cultural psychology vol. 49,7 (2018): 1081-1097. doi:10.1177/0022022118774925