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 about 10 years ago

Inbar Rose‭

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