It started as a "What if...?" kind of thread on RPG.net. Greg found cool new things to add, then even cooler new things, then added a whole mountain of cool things on top of that.
Progenitor is a massive campaign sourcebook for Wild Talents. It all starts with Amanda Sykes, a young, midwestern American housewife, who in 1968 gains incredible powers from an infusion of "dark energy." Trying to find ways to use these abilities to help her country, she unwittingly passes them on to others -- her husband, her daughter, an Army recruiter, Vietnamese guerillas, President Johnson. Each of them in passes powers on to others in turn.
As the powers spread, the world changes. Amanda fights to protect young American soldiers in Vietnam, and creates among their enemies some of the most powerful superhumans on the planet. Impossible technologies flourish. Metahuman-crafted memes change society. A metahuman builds an island of her own, dubs it Atlantis, and makes it a haven for the Progenitor's heirs. Another plots to send his nation into outer space and seed the Solar System with Earthly life. A relatively minor, anonymous metahuman sparks the Metapocalypse in 1983, ultimately resulting in a billion deaths out of sheer spite; it would have been more if not for Amanda Sykes.
Player characters can begin at any moment in the timeline. Progenitor features a thoroughgoing history of the world after 1968, plus rules for the GM to change that timeline year by year to reflect the shifting tensions and priorities in society. Game metrics for Warfare, Economy, Suspicion and Technology define crises for the player characters to face. And of course there are detailed stats and backgrounds for characters in every era, from the wicked Jack Grimes to Amanda Sykes, the Progenitor herself, who evolves into something altogether other than a modest housewife over the years.
