Darwin's ideas
The key is that it has to be a completely new idea, not an extension of an existing model.
Speaking just to Darwin, he didn't come up with his ideas in a vacuum - they were an extension of an existing, although disfavored, model. The Wikipdia article on Alfred Russel Wallace (
http://en.wikipedia.org/wiki/Alfred_Russel_Wallace#Early_evolutionary_thinking) lists off a handful of pre-Darwin proponents of evolution.
IMHO some distance in time is necessary to determining whether something constitutes a breakthrough - there's not enough historical perspective to assess the long-term impact of an idea that's only been around a short time.
