RPGMemes

Technically it implies that all these other races are diverged near humans, humans being relatively unchanged remain close enough to produce viable offspring, but with different non human races being diverged from each other to the point of non viability.

So basically the racial map for a D&D setting would have humans at the center, with half children in each of the spokes of a wheel, and every non human race being nodes located in the environment where they developed in extremity, and then from there you can build the environment under the premise of the conditions that developed elves or dwarves or orcs from the human starting point.

This would also have to include a backstory spanning tens of thousands of years.