Quote Originally Posted by mariosmentor View Post
Compilation of Final Fantasy VII
Centuries after the events of X/X-2, the people of Spira invent space travel, and move to Gaia, the setting of Final Fantasy VII. It is here where Shinra’s descendents manage to perfect their ancestor’s hypothesis and use Mako energy to power the metropolis known as Midgar.
I think people expand this theory too far, but I just read the following on the Final Fantasy VII wiki:

Kazushige Nojima, along with Yoshinori Kitase, has stated in the Final Fantasy X-2 Ultimania interview that Final Fantasy X's Spira is the 'ancestor' civilization which colonized the Planet of Final Fantasy VII. This is reinforced by Shinra's mention of potentially harnessing the Farplane as an energy source, which his descendants would go on to do with the Lifestream many centuries later, as the Shinra Electric Power Company.
Which supports that one small part of your theory, except you added space travel. The Shinra→Shrina Electric Power Company link is cool.