forerunner

/ˈfɔrˌrʌnər/
noun
  1. A person or thing that comes before and is a sign of what is to follow; a precursor.
    • Early jazz musicians were forerunners of rock and roll.
    • The first smartphone was a forerunner of today's advanced devices.
    • The steam engine was a forerunner of modern trains.
  2. A person who runs ahead of others, especially in a race or as a scout.
    • The forerunner reached the finish line first, winning the race.
    • In the marathon, the forerunner set a fast pace for the others to follow.
    • The forerunner checked the trail for obstacles before the main group arrived.