A return to an older way of doing something—or an old characteristic that reappears—is a throwback. If you like dressing in bell bottoms and leisure suits, your style is a throwback to the 1970s.
The noun throwback can be a less-formal way to say atavism. Both words describe a reversion to something that was done (or existed) in the past. If you have red hair like your great-grandmother, you can call that trait a throwback. In sports, a throwback uniform is one that mimics an older style, worn by teams in the past. In biology, a throwback is a trait that returns after having been lost through evolution.