Alternatively, suppose that the male himself will assist in feeding and protecting the young, and in hunting cooperatively with the female. Then the female and the male must assess each other's parenting and hunting skills and the quality of their relationship. All these things are hard enough to assess, but it is even harder for the female to assess a male when he provides nothing but sperm and genes, as is the case with male bowerbirds. How on earth is an animal to assess a prospective mate's 8£nes, and what have blue fruits to do with good genes?
Animals do not have the time to produce ten offspring with each of many prospective mates, and to compare the outcomes (the eventual number of surviving offspring). Instead, they have to resort to shortcuts by relying on mating signals such as songs or ritualized displays. As I shall discuss at more length in Chapter Eleven, it is now a hotly contested problem in animal behaviour to understand why, or even whether, those mating signals serve as veiled indicators of good genes. We have only to reflect on our own difficulties in selecting mates and in assessing the true wealth, parenting skills, and genetic quality of our various prospective partners.
In this light, reflect what it means when a female bowerbird finds a male with a good bower. She knows at once that that male is strong, since the bower he assembled weighs hundreds of times his own weight, and since he had to drag some individual decorations half his weight from dozens of yards distant. She knows that the male has the mechanical dexterity needed to weave hundreds of sticks into a hut, tower, or walls. He must have a good brain, to carry out the complex design correctly. He must have good vision and memory to search out the required hundreds of decorations in the jungle. He must be good at coping with life, to have survived to the age of perfecting all those skills. He must also be dominant over other males—since males spend much of their leisure time trying to wreck and steal from each other's bowers, only the best males end up with intact bowers and many decorations.
Thus, bower-building provides a comprehensive test of male genes. It is as if women put each of their suitors in sequence through a weight-lifting contest, sewing contest, chess tournament, eye test, and boxing tournament, and finally went to bed with the winner. By comparison with bowerbirds, our efforts to identify mates with good genes are pathetic. We grasp at external bagatelles like facial features and ear lobe lengths (Chapter Five), or like sex appeal and Porsche ownership, which tell nothing about intrinsic genetic worth. Think of all the human suffering caused by the sad truth that beautiful sexy women or handsome Porsche-owning men often prove to have miserable genes for other traits. It is.-no wonder that so many marriages end in divorce, as we belatedly realize how badly we chose and how flimsy our criteria were. How did bowerbirds evolve to use art so cleverly for such important purposes? Most male birds woo females by advertising their colourful bodies, songs, displays, or offerings of food, as dim indicators of good genes. Males of two groups of birds of paradise in New Guinea go one step further by clearing areas on the jungle floor, as bowerbirds do, to enhance their displays and show off their fancy plumage. Males of one of those birds of paradise have gone still further by decorating their cleared areas with objects useful to a nesting female: pieces of snakeskin to line her nest, pieces of chalk or mammal faeces to eat for their minerals, and fruits to eat for their calories. Finally, bowerbirds have learned that decorative objects useless in themselves may nevertheless be useful indicators of good genes, if the objects are ones that were difficult to acquire and keep.
We can easily relate to that concept. Just think of all those advertisements showing a handsome man presenting a diamond ring to a seemingly fertile young woman. You cannot eat a diamond ring, but a woman knows that the gift of such a ring tells far more about the resources that her suitor commands (and might devote to her offspring and herself) than a gift of a box of chocolates would tell. Yes, chocolates provide a few useful calories, but they are quickly gone and any idiot can afford to buy them. In contrast, the man who can afford that inedible diamond ring has money to support the woman and her kids, and also has whatever genes (for intelligence, persistence, energy, etc.) that it took to acquire or hold on to the money.
Comparisons of different bowerbird species and their bowers show that male bowerbirds achieve through bowers what other birds achieve through bright plumage. Bowerbird species differ in the conspicuousness of adult male plumage. For example, males of the five species that build towers or huts sport brilliant yellow-orange crests, whose lengths vary among the species from 4 inches to nothing at all. The shorter the crest, the bigger the bower, and the more numerous and diverse its decorations. It makes sense that a male whose manly ornament is reduced to a runty 2 inches should go to great lengths to compensate in other ways.
Thus, in the course of bowerbird evolution the less resplendent males have lured the female's attention from ornaments that are permanent parts of the male's body to ornaments that the male gathers. Whereas sexual selection in most species has produced differences between males and females in their bodily ornaments (Chapter Six), in bowerbirds it has shifted towards causing males to emphasize collected ornaments separate from their bodies. From this perspective, bowerbirds are rather human. We, too, rarely court (or at least rarely initiate courtship) by displaying the beauties of our unadorned naked bodies. Instead, we swathe ourselves in coloured cloths, spray or daub ourselves with perfumes and paints and powders, and augment our beauty with decorations ranging from jewels to sports cars. The parallel between bowerbirds and humans may be even closer if, as friends of mine who are into sports cars assure me, duller young men tend to decorate themselves with fancier sports cars.
Now let's re-examine, in the light of bowerbirds, those three criteria supposedly separating human art from any animal production. Both bower styles and our art styles are learned rather than inherited, so that there is no difference by the third criterion. As for the second criterion (doing it for aesthetic pleasure), it is unanswerable. We cannot ask bowerbirds whether they get pleasure out of their art, and I suspect that many humans who claim to do so arejust putting on cultural affectations. That leaves only the first criterion: Oscar Wilde's assertion that art is useless, in a narrow biological sense. His statement is definitely untrue of bower art, which serves a sexual function. But it is absurd to pretend any longer that our own art lacks biological functions. Instead, there are several ways in which art helps us to survive and to pass on our genes.
Firstly, art often brings direct sexual benefits to its owner. It is not just a joke that men bent on seduction invite a woman to view their etchings. In real life, dance and music and poetry are common preludes to sex.
Secondly, and much more importantly, art brings indirect benefits to its owner. Art is a quick indicator of status, which—in human as in animal societies—is a key to acquiring food, land, and sexual partners. Yes, bowerbirds get the credit for discovering the principle that ornaments separate from one's body are more flexible status symbols than ornaments that one has to grow, but we still get credit for running away with that principle. Cro-Magnons decorated their bodies with bracelets, pendants, and ochre; New Guinea villagers today decorate theirs with shells, fur, and bird-of-paradise plumes. In addition to these art forms for bodily adornment, both Cro-Magnons and New Guinea villagers produced larger art (carvings and paintings) of world quality. We know that New Guinea art signals superiority and wealth, because birds of paradise are hard to hunt, beautiful statues take talent to make, and both are very expensive to buy. These badges of distinction are essential for marital sex in New Guinea: brides are bought, and part of the price consists of luxury art. Elsewhere as well, art is often viewed as a signal of talent, money, or both. In a world where art is a coin of sex, it is only a small further step for some artists to be able to convert art into food. There are whole societies that support themselves by making art for trade to food-producing groups. For example, the Siassi islanders, who lived on tiny islets with little room for gardens, survived by carving beautiful bowls that other tribes coveted for bride payments and paid for in food.