Charles Darwin's explanation for the adornment of males in fancy-male species was that females select for mates highly adorned males on the basis of a human-like aesthetic sense -- beauty for the sake of beauty.

Darwin made few, if any, observations of the behavior of animals in the wilds. His observations of birds, for example, were mainly through the sight of a gun. Had Darwin observed animals in the wilds, he would have discovered that the colors of males are employed in territorial spacing.

In the mating season, what appears to be choice of mates on the basis of appearance of the males largely represents choice of reproductive territory on the part of the females, as well as the males. I became aware of this in field observations of dragonflies in the 1950s.

This discovery was later extended to include other insects and birds. Out of these observations came a view that food in the territories of the males determines male mating success, as the females are attracted to the specific foods found in the territories of the males. The males of some birds, such as bowerbirds, actually place foods of specific colors (red, green, or blue, depending on the species of the bird) in their mating courts.

Among many birds, males feed their specific foods to potential mates during courtship. This leads to segregation of males and their mates from other males and their mates in the mating system. This system leads to genetic segregation and species formation, as individuals of specific tastes and physiologies meet mates of similar genotypic characteristics. I call this the food-courtship theory of speciation.

It is pointed out that even pictures of foods, such as flowers and fruits, as represented on the plumage of the male, may specifically attract a female to a male. This food-courtship theory is one of the main contributions of the book. It suggests that mating systems of wild animals are based on plain, old-fashioned home economics, rather than abstract art.

In the book, I also question whether wild animals experience consciousness of beauty, for the sake of beauty, as humans do. This is particularly treated in Chapter 7 (Natural Ingenuity and the Origin of Consciousness). This chapter also deals with implications of sexual selection in human populations, as related to humanity's place in nature.