User blog comment:Ynwa244/Unstable Star/@comment-1679409-20120508191634

From what I've read, this was originally going to be the reasoning behind the Reapers' actions. They knew that the growth in dark energy could destroy everything, so they harvest the sapient races, mergining their minds together in hopes they can find a solution. This is also why humans are seen as so important: their genetic diversity may give them the ability to come up with the solution.