Explaining "Half-Breeds" in a world with multiple races

In a hypothetical world where multiple humanoid races develop independently of each other (such as a world that contains Elves, Dwarves, and Humans for instance) what are the conditions for half-breeds to be possible?

In our world;

• Dogs can produce offspring by mating with any other breed within their species, producing half-breeds or "mutts" which can create whole new breeds and continue reproduction.
• Horses and Donkeys can breed together to produce Mules, which cannot reproduce on their own.
• Animals from very different species can not breed together, such as an Elephant and a Giraffe.
• Humans can breed with other Humans, but not with Monkeys or Apes with whom they share ancestry.

Under what conditions could a new "half-breed" race develop between two races? (Such as Humans and Elves creating Half-Elves) One that would be consistent in it's outcome, (A Human and an Elf always breed a Half-Elf) and the resulting offspring's race. (Half-Elves are always the same). One that would also prevent continuous branching. (Like Dog breeds which continue to create new breeds all the time)

posted over 9 years ago

Inbar Rose‭

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