Well, we all know Ax instantly dismissed humans learning about Z-space because "they're too inferior, after all" but even when it is revealed that this is not so, and humans really HAVE discovered Z-space, we never learn HOW they did so. Here's my take on it.
Ax messed with Marco's dad's computer in #8. The Alien, so what if, maybe, just maybe, THAT was what helped Marco's dad discover Z-space? I KNOW, the technology was erased later, but they DID have it for a short time, and a LOT of people probably saw it, and Marco's dad is no idiot either. What if that was the reason Z-space was found out? It would make a lot of sense, especially since Ax would have been responsible for a HUGE advancement in human society, one he caused, accidentally yes, but one he still caused.
Opinions?