1. 先驱；先锋；前身
A precursor of something is a similar thing that happened or existed before it, often something which led to the existence or development of that thing.

1. something that precedes and indicates the approach of something or someone

Synonym: harbingerforerunnerpredecessorherald

2. a person who goes before or announces the coming of another

Synonym: forerunner

3. a substance from which another substance is formed (especially by a metabolic reaction)