Hey, I like to think of fantasy races like elves, dwarves, goblins, etc, as closely related species/subspecies of humanity, like modern humans and Neanderthals. But what kind of evolutionary pressures could result in these populations. isolated from the rest of mankind, to develop the iconic physical features and traits that we associate with them, like females as strong or stronger than the males, smaller size, increased fertility, unusual skin/hair colors, significantly longer or shorter natural lifespans, etc? What advantages would they bring? Does anyone have any ideas for my little thought experiment?

I am a writer/ world builder, you see, and this stuff is fun to think about.