|Waiting on the Hyperspace Pizza Nexus|
Or telepathy. Does it really matter just how humanity develops this mental power? What's interesting is how the "normals" react to the espers...or whether the entire race becomes telepathic. Then what happens? Well, for one thing, speech pathology is no longer the go-to career for former actresses.
The importance of effects over causes is one of the big reasons to be wary of the "info dump" - the deep-seated urge to explain your entire world to the reader in one or two bloated, digressive paragraphs. Pay more attention to what happens next than what happened before.
Of course, even though causes aren't sufficient, they are necessary. They determine the limits of the effects we describe. If our spaceships can reach other star systems, but only have Bussard ramjets, and not hyperdrives, the empire we create would be much, much different from one based on faster-than-light travel. If our telepathy comes in over-the-counter pill form, the effects will be radically different from a future of rare genetic telepaths.
Causes define our stories; effects are the reasons we write them.