Clinical judgment and sometimes ethical judgment enter into these decisions where there are often no right or wrong answers and where there are no textbooks or RCTs that tell us what to do.
predecessor - something that precedes and indicates the approach of something or someone. harbinger, herald, forerunner, precursor. indicant, indication - something that serves to indicate or suggest; an indication of foul play; indications of strain; symptoms are the prime indicants of disease.
ancestor. 1  any person from whom one is descended, esp. one earlier in a family line than a grandparent; forefather; forebear. 2  an early type of animal from which later kinds have evolved. 3  anything regarded as a precursor or forerunner of a later thing. 4  Law the deceased person from whom an estate has been inherited.