In regards to the organic vs mana manifestation discussion, it appears Innistrad wurms are mana manifestations.

Can you spell retcon?

The world of MTG is fueled by magic. I don't think there is a big (if any) difference between "magical red-mana firebreathing" and "exothermic chemical reaction" in it. Entire universe consists of flebontinium, and you can throw away the physics, chemistry, biology, and ecology of our world away. However, we aren't given any clear answers of how "physics, chemistry, biology and ecology" of MTG work.
And that's terrible.

Skywhale corpses sink up.

Presumably there are aether hagfish to eat the corpses

I thought this thread died.

It did, but the aether hagfish never got around to eating it.

I'm assuming that much of the natural laws are still in place just aided by whatever magical laws are in place.

But not always. Serra's Realm and Mirrodin both operate with different laws of certain constants.

True, but unless it's a pure magical dimension the plane must have some form of natural law in place. There has to be a solid foundation before you can build.

In those cases, the differences had to be pointed out. It's a fairly safe assumption that any particular fictional setting is like reality, unless noted. Gravity still works, human biology is about the same, and I can trust an arrow shot from a bow to travel through the air.

Come to think of it, hybrids of virtually any race may be possible because of Mana.

Most of the time, it takes either genetic manipulation or reality altering magic to make hybrids.

Not true. Hybrids between sentients are apparently a thing throughout the multiverse. This is heavily implied and even discussed to some extent in the books.

I can think of a grand total of three.
Radha, Fonn, and Soramaro.
There's also the potential of half demons in Ravnica, but Malfegor is a less clear organism.

We know for absolute certain it's incredibly rare for hybrids to happen, and the extent to which it even can happen is never really talked about.

In the Old Ravnica books, the ones with Kos, there is a whole tribe of Gruul that is made primarily of hybrids. In fact, you could say that for the entire guild. And the Gruul tend to do things the old-fashioned way.

In the Planeswalker book, Xantcha talks about how races prefer to mate with their own, but hybrids do occasionally happen. And this is someone who has visited many worlds.

In the Odyssey books, yeah I know they suck, they are a few unnamed hybrids that the books mentioned in passing.

I can quote you on all of this as I have all but three Mtg books. Not right now, as I am typing this in my dorm in college, but I can do once I get back home.

So consider adding 'ogre' to that list of possible overlap (because I seem to recall that specifically) but this doesn't alter the fact that it doesn't specify what races viably can intermix nor the frequency.

A viashino human, to just pick two, isn't likely going to happen.

That's putting the cart before the horse. You're extrapolating two unconnected things and declaring them intertwined. Does it possibly happen? Sure, but our observable data suggests it is Rare beyond rare, and the number of viably crossable species is EXTREMELY limited. You can't make a blanket statement about hybrids because a half-elf exists.

Look at all the other hybrid creatures:
gaea's skyfolk and razorfin hunter are creatures created by the overlay. (okay, razorfin, maybe less, but there was a theme going on there) Vorel, Experiment One, and Delver of Secrets are direct result of manipulation.

I'm not saying it doesn't happen, but it's clear that wizards has no intention for it to be something widespread, much less common. The fact that wotc doesn't just go Star Trek with mixing species is one of the things that's good about their IP. So, the assumption should probably always be "can't" rather than "can".

This is the Cabal we're talking about. I wouldn't rule out genetic tampering. Or that there was consent to ANYTHING.

Wait, Soramaro? Can you tell me more about that?
From the top of my head, there's also Immugio from The Final Sacrifice who is the son of a Gray Ogress and a Stone Giant. I'm not sure about Kaysa, I think she might be a half elf, but IIRC her backstory is pretty different in pre- and post-revisionist continuity, which keeps confusing me... But yeah, as far as we know, hybrids are pretty rare. The Ravnica books say that the humans there mixed with many other races, but Ravnica seems to be an exception, which makes sense as it's extremely diverse and densely populated. I really wouldn't mind if the concept of hybrids was explored more often and we even got to see them on cards once in a while. I just wish they'd type all half elves as frigging Human Elf instead of just Elf.

Sure.
In the deck insert, it talked about how he was a human/moonfolk hybrid, and the Soratami found him fascinating (in a sort of talking dog way) until eventually he actually earned their respect. When he died, he became a kami.

Kinda can't count that. It might not be contradicted, but that was definitely done out of house, so we absolutely can't use it as a means to determine WotC policy on hybrids.


I mean, I'm arguing against it, but not that hard. My biggest concern is just the special snowflake possibilities.
As for the type line, that's probably never going to happen. It might, but space is a premium, and until Innistrad, human was a nonsupported catch all for mechanics. It actually irritates me they've declared human counts as White's characteristic.

Said Gruul tribe also had viashino humans as well. Xantcha has lived a long time and visited many worlds so I'm convinced she saw her fair share of hybrids to not even talk about the possibility of hybrids. Are they common? NO, but certainly not rarer than rare.

I mean, yeah, they really are. You have to take multiple worlds worth of populations to make this argument.
Even from there, step out to look at the concentration of their appearances in the ~25 years worth of material and the number of characters we've had. They're staggeringly outnumbered.