Did Jews celebrate Bar Mitzvahs in ancient time?

Answer

First, let's understand what the words "Bar Mitzvah" actually mean. The phrase literally translates to being "son of obligation" -- i.e. the person is now obligated to follow the mitzvot of the Torah.

Although we commonly refer to having a "Bar Mitzvah," technically speaking, this is impossible. The term "Bar Mitzvah" refers to a status, in the same way being a student or being a parent is a status. One is either Bar Mitzvah or not, but one cannot "have" a Bat Mitzvah.

A Jewish boy automatically becomes Bar Mitzvah when he turns 13 years old (and a girl at age 12). This is true whether there is a Bar Mitzvah celebration or not.

This would have true in AD 100, as it is true today.

Colloquially speaking, when people say, "I had a Bar Mitzvah," it means that they said the blessings over the Torah in synagogue. The reason why the Bar Mitzvah boy receives this privilege is simply to notify the congregation that he is now "obligated in mitzvot" and that he can be counted in a prayer quorum.

To learn more, read "Bar/Bat Mitzvah and Beyond" by Rabbi Nachman Cohen (published by Feldheim).