The book is all about why cultures vary in their consumption of food, shelter and clothing. Most of the cultural differences in consumption are due to climate differences (Arctic, Temperate, and Tropical).
For example, there are sharp differences in diet, clothing and shelter between Northern Europe and Southern Europe. This is due to genes adapting to what local resources are available for food, shelter and clothing.
The book also provides an explanation of the cultural differences between the North and the South regarding punctuality, individualism, social distance or territorialism (turf), and the role of women in society.