The phrase "early proponent" refers to someone who supports or advocates for a particular idea, concept, or cause at an early stage or before many others believe in it or are aware of it. Full definition
The ethanol market did not take off as early proponents hoped due to issues of cost, portability, and energy density (miles per gallon). (globalwarming.org)
Many large organizations have embraced such regulations, including the NFL (where «The Rooney Rule,» is named for early proponent and Pittsburgh Steelers owner Dan Rooney), Pinterest, Facebook and RBC, the latter of which has a goal of granting half of new executive appointments to women and one in five to members of visible minority groups. (canadianbusiness.com)
His suggestion here reminds me of yet another Harvard scientist: the botanist Asa Gray, the first American Darwinian and also an important early proponent of what is often called «theistic evolution.» (firstthings.com)