"It's because we come from the Stone. When we come out of our mothers, we're small, round rocks. Pink-streaked rocks are girls, and gray ones are boys. The rocks must be dipped in lava for a few moments each day to keep warm. Every year, a few unlucky parents drop the rock into the lava and can't get it out. Very sad. But do it right, and in a few weeks, the rock cracks open, revealing a bouncing dwarven baby."