Isabel Wilkerson's The Warmth of Other Suns is truly a labor of love. It took 15 years to research and write, as she interviewed over 1,200 people. Wilkerson tracked down her subjects at churches, quilting clubs, funerals, family reunions, and others. After preliminary rounds of interviews, she narrowed her search down to 30 people, and then chose the three main subjects who appear in the book.
Guns, Germs, and Steel: The Fates of Human Societies, is his attempt to answer not just Yali's question, but the whole question of why some peoples in some parts of the world developed technological advances before others, and why some of them were then able to conquer other peoples using those advances.