Recent studies have produced a variety of advances in the investigation of genetic similarities and differences among human populations. In this reprinted article, originally published in Human Biology in 2011 (vol. 83, no. 6, pp. 659–684), I pose a series of questions about human population-genetic similarities and differences, and I then answer these questions by numerical computation with a single shared population-genetic data set. The collection of answers obtained provides an introductory perspective for understanding key results on the features of worldwide human genetic variation. A new foreword discusses the original article in light of the research that has followed.