Sometimes an idea needs to be published twice so that a second generation can judge whether it makes sense. In 1958, almost three decades after the first edition, Fisher produced a second edition of The Genetical Theory of Natural Selection. This time it took root in the minds of a new, more mathematically skilled generation of young biologists such as John Maynard Smith and Peter O'Donald. They saw what Fisher was getting at: one could think seriously about the evolutionary origins of sexual preferences, and their evolutionary effects. Maynard Smith set about studying the courtship dances of fruit flies. He found that highly inbred, unfit males could not keep up with healthy females, so would be rejected as mates. The females seemed to be choosing for male fitness as evidenced by dancing ability. Maynard Smith also spent the next several decades wondering why sex evolved in the first place. O'Donald explored the mathematics of sexual selection throughout the 1960s and 1970s, trying to develop proofs of Fisher's intuitions.
A rivulet of interest in sexual selection started to flow through the minds of leading biologists. In his widely read Adaptation and Natural Selection of 1966, the young theorist George Williams used Fisher's sexual selection ideas to interrogate the concept of an evolved adaptation. Sexual selection was found not guilty of debauching evolution and making species degenerate. Williams put ornaments on an equal footing with other adaptations, giving sexual selection a status equal to that of selection for survival. In expanding and clarifying the definition of biological adaptation, Williams helped to overcome the machine aesthetic of the Modern Synthesis, and its emphasis on ornaments as species-recognition markers.
Finally, the reductionistic behaviorism of previous decades gave way to cognitive psychology in the 1970s, Once again it became respectable to talk about the mind. Cognition, choice, judgment, decsion-making, and planning became part of psychology once again. This laid the foundation for the modern understanding of mate choice in general.
An increased acceptance of the role of female choice may have also been due to social trends. The sexual revolution of the 1960s and the rise of feminism led to more women studying and contributing to biology, and to a new appreciation of female choice in human social, sexual, and political life. Married male biologists could no longer take for granted the obedient support of their wives. They faced a new world in which women made choices more consciously and took more control of their lives. Although evolutionary theory was still extremely male-dominated, individual males were feeling more pressure from female choice. Female biologists doing field-work also drew more attention to female choice among the animals they studied. This was especially important in primatology, as women such as Jane Goodall, Dian Fossey, Sarah Hrdy, Jeanne Altmann, Alison Jolly, and Barbara Smuts explored female social and sexual strategies. Dismissing the idea that female choice could influence the direction of evolution began to look both sexist and unscientific. By drawing attention to the evolution of social and sexual behavior in animals, the sociobiology of the 1970s did for the study of animal sexuality what feminism did for the study of human sexuality. It empowered thinkers to ask "Why does sex work like this, instead of some other way?"
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