Were there always teams in road racing?
In this interesting video about the history of the Tour de France, at some point the narrator explicitly mentions the period (during the 70s if I remember well) when great cycling events beginned to change from a one-to-one fight amongst a few super-strong riders (typical example: Merckx) to a teamwork fight amongst well-orchestrated, hierarchical teams (typical example: Armstrong).

I think (and the video also mentions it) that this is due, among other things, to an increased understanding - and acceptance - of the importance of aerodynamics (LeMond), and also to advances in scientific training, which leveled the differences between well-prepared riders, I think.

Also, the role of the team in one or another era can be inferred from the very title of another excelent video, "Stars and Watercarriers".