Pellatarrum: My Humans Are (Kinda) Different

I actually didn't plan on doing this one. I know that I've owed you elves for years now, but this is actually an outgrowth of me thinking about elves.

It's interesting that throughout D&D and later Pathfinder, humanity is the only playable race that has children with other races. Sure, there are half-dragons, and the obligatory half-angels and half-devils, but there are no (for example) elf-dwarf hybrids. Why is that?

And that's how this post came about.


Why do half-elves exist?
In Pellatarrum, the reason humans can interbreed with so many races is because the dwarves built them to be highly adaptable. They were, after all, meant to be ambassadors to the elves, who are best described as "fey". Or, in other words, "Powerful, possessed of violent whimsy, and terrifyingly random." The ability to adapt to such an harsh environment was a deliberately engineered survival trait. This explains a lot about humans: why they live all over the place, why they easily form bonds with other races, and yes, why they can interbreed with non-humans.

Inter-fertility with elves is generally believed (though it's never been stated outright) to have been another design choice.  It's often said that the worst thing the dwarves ever did to the elves was to introduce them to humans. Prior to that, the elves didn't think anyone could ever be as beautiful as they were; all other races were hideous. But humans, by virtue of being both highly adaptable and made (somewhat) in the image of elves, were both similar enough to be beautiful and different enough to be exotic that many elves became distracted by them, if not enraptured with them.

How is this represented mechanically?
If you want to represent this, use the Heart of the Fey trait:

Heart of the Fey: You gain low-light vision, gain a +1 racial bonus on Reflex and Will saves, and treat Knowledge (nature) and Perception as class skills. This racial trait replaces skilled. 

However, not all Pellatarran humans still have this trait. Due to their adaptability, their children's traits can change according to their environment, and so any racial trait is available (and sometimes different traits express themselves through children of the same family).

What about half-orcs?
The existence of half-orcs and other human hybrids is generally explained as "Well, adaptability is broad like that. Not an intended consequence, mind you, but it's not a terrible thing for the peoples of the world to become more dwarven in nature."

Why aren't there any half-dwarves?
Again, design. While other elder races saw their creations as tools, cannon fodder, or slaves, the dwarves thought of them as members of their own clan, highly functional but tragically maimed by circumstance and purpose. Interbreeding with them would be too much like interbreeding with a beloved pet or working animal.

Why are humans infertile with gnomes? 
The general consensus is "thrice-damned random fey witchcraft interacting oddly with fine dwarven craftsmanship." This argument is somewhat bolstered by the odd manner in which gnome-halfling pairings resolve, where any children are always the same race as their same-gender parent.

What about humans and halflings?
This always results in more halflings, albeit larger than usual: 4 feet tall or more,  and weighing between 30 and 35 pounds. (For those keeping track of such things, this explains the "Tallfellow" branch of the halfling family tree.

Is there anything in D&D/Pathfinder that a human won't have sex with?
Honestly, probably not.