In human's ability context, past inventions,quality,present and future relevance are the common measurements criteria to evaluate a person's ability to invent.
In other opinion, it depends, its matter of what kind of inventor you are looking? then define the parameters, a person requires for further research to
invent?
If runner is expected? then what type of runner? who can run inside water like Shark? or on the field like Cheetah? or in dense forests like monkeys?
Ability of person who measures other person's ability to invent is also a vital factor. Proper home work need to be done before evaluating ability of another person to invent. Researcher with good past record need not to be most feasible candidate for future invention.
For example, in fundamental research, there are many scientists who have thousands of research work published or patented that's much more than greats like Newton, Einstein, Alva Edison etc... Still identified greats are great because of quality work what they have done.
Then how can we measure Einstein, Newton, Tesla and today's lacks of inventors working across the globe with same measurement parameters? is it fluke? For that we need to understand what we want? Then see the potential by past performance, present capability and future vision and out of box creativity. At the end, i would say, its contextual and it varies, a person without formal education can have potential to invent something great. And a highly educated researchers sitting in well equipped labs also sometime unable to think out of box, although they have good records in past.