Read Online Why is Sex Fun?: the evolution of human sexuality by Jared Mason Diamond - Free Book Online

copulation, secure in the knowledge that his deserted female sex partner will be able to handle all the ensuing work of promoting the survival of his genes. Human infants virtually need biparental care, especially in traditional societies. While we shall see in chapter 5 that activities represented as male parental care may actually have more complex functions than meet the eye, many or most men in traditional societies do undoubtedly provide services to their children and spouse. Those services include: acquiring and delivering food; offering protection, not only against predators but also against other men who are sexually interested in a mother and regard her offspring (their potential stepchildren) as a competing genetic nuisance; owning land and making its produce available; building a house, clearing a garden, and performing other useful labor; and educating children, especially sons, so as to increase the children's chances of survival.
    Sex differences in the genetic value of parental care to the parent provide a biological basis for the all-too-familiar differing attitudes of men and women toward extramarital sex. Because a human child virtually required paternal care in traditional human societies, extramarital sex is most profitable for a man if it is with a married woman whose husband will unknowingly rear the resulting child. Casual sex between a man and a married woman tends to increase the man's output of children, but not the woman's. That decisive difference is reflected in men's and women's differing motivations. Attitude surveys in a wide variety of human societies around the world have shown that men tend to be more interested than women in sexual variety, including casual sex and brief relationships. That attitude is readily understandable because it tends to maximize transmission of the genes of a man but not of a woman. In contrast, the motivation of a woman participating in extramarital sex is more often self-reported as marital dissatisfaction. Such a woman tends to be searching for a new lasting relationship: either a new marriage or a lengthy extramarital relationship with a man better able than her husband to provide resources or good genes.

body { margin-right: 8pt; } h1,h2,h3,h4,h5,h6 { text-align:center; page-break-after: avoid; page-break-inside: avoid; } .section_image { page-break-inside: avoid; display:block; text-align:center; } .body_image { page-break-inside: avoid; display:block; text-align:center; } .epigraph { font-style: italic; page-break-inside:avoid; margin: 0.5em 0px; margin-bottom: 1em; font-size:0.9em; } .epigraph_author { margin-left: 1em; font-size:0.85em; margin: 0.6em 0px; margin-left: 2em; } body.cover { margin: 0px; padding: 0px; } svg.cover-svg { height: 100%; width: 100%; } img { max-width: 95%; } div.img { padding: 3px; text-align: center; } div.title1 { page-break-after: avoid; page-break-inside: avoid; font-weight: bold; margin: 1em 0px 0.5em 0px; font-size: 1.4em; text-align: center; } p.title-p { margin: 0px 0px 0.5em 0px; } div.title2 { page-break-after: avoid; page-break-inside: avoid; font-weight: bold; margin: 1em 0px 0.5em 1.5625em; font-size: 1.1em; } div.title3 { page-break-after: avoid; page-break-inside: avoid; font-weight: bold; margin: 1em 0px 0.5em 1.923em; font-size: 1.0em; } p { margin: 0px; margin-top:0; margin-bottom:0; text-indent: 1.5em; text-align: justify; } p.subtitle { font-style: italic; page-break-after: avoid; page-break-inside: avoid; font-weight: bold; text-indent: 0px; margin: 0.5em 2em; text-align: center; } p.empty-line { height: 1em; margin: 0px; } a { vertical-align: super; line-height: 0.1; font-size: 0.7em; } div.annotation { font-style: italic; margin: 0em 0px 0em 0em; text-indent: 0px; font-size:smaller; } div.citation { font-style: italic; margin: 1em 0px 1em 2em; text-indent: 0px; } div.poem { margin: 0.5em 15% 0.5em 15%; text-align: center; } div.stanza { page-break-inside: avoid; margin: 0.5em 0px; justify: left; } p.v {