It is interesting that as far back as the Mishna, there was a concern about assimilation. The Talmud in מסכת גיטין described the difficult life Jews had to endure under the Romans. There were times when things were so bad, that Jews sold themselves to the Romans in order to make money. The Rabbis did not want people to make a habit of this. If someone did this three times, they would not redeem them. They also made a point regarding the children. As long as they were with their father, they were protected. If the father died, however, they would redeem the children, for fear of קילקול, which is translated as assimilation. If they were to remain among negative influences, they would learn from their evil ways. So we see, Jews always needed to be on guard so that they not learn from Gentile practices.