@zhivik - I think either of your options could be possible...or both at once, that the parallel universe is a living horror who's black beating heart beats a five thousand year pulse where magic is just the plasma run-off oozing from parallel dark energy wounds. But yeah, all just speculation at this point. What we need, to push the envelope here, is some canon that links mana, mana levels/cycles, to sub-atomic particles, including but not limited to, string theory, m-theory, etc. At this point canon evidence is pretty solid on the cycle, that there can be spikes and dips, and that there are meta-planes beyond the Astral. But after that...well, levitate spell would be the best place to start, I guess (at least for me with physics background, ignite may be a better starting point of the chemists, and so on). What's the force (old school F = ma) of a levitate spell cast at X force (Shadowrun force)? Max force, min force, etc. I don't have books but would be interesting to see what it translates into and then explore from there.
@Rockopolis - I think Charybdis is right. The other way to answer your question is; Yes, it is significant. How so? Well, homo sapiens sapiens are the default form for homo sapiens during low magic cycles. The question answers itself. Now asking "why" are homo sapiens sapiens the default form at least lets one make hypothesis about it, and then test those hypothesis...which in SR canon they did...and like Charybdis pointed out they discovered it's dependent on DNA. Then comes the questions; which genes or segments of the DNA are responsive to magic levels, how are they passed on during low mana cycles, etc.