There is extensive evidence that vertebrates of all classes have the ability to control the sexes of the offspring they produce. Despite dramatic differences in the mechanisms by which different taxa determine the initial sex of offspring, each group has found its own way of adjusting offspring sex ratios in response to social and environmental cues. For example, stress is a well-known modulator of offspring sex in members of all groups studied to date. Food availability, and limitation in particular, is another common cue that stimulates biases in offspring sex ratios in a wide variety of species. Offspring sex can be adjusted at the primary level, which occurs prior to conception, or at the secondary level, during embryonic development. While the mechanistic pathways that ultimately result in sex ratio biases and the developmental time-points sensitive to those mechanisms likely differ among taxa, the key involvement of steroid hormones in the process of sex ratio adjustment appears to be pervasive throughout. This book reviews the systems of sex determination at play in different vertebrate groups, summarizes the evidence that members of all vertebrate taxa can facultatively adjust offspring sex, and discusses when and how these adjustments can take place.

In this completely updated and revised edition of this international best-seller, Dr Shettles shows you how to raise the chances of having a child of the sex you want, from 50 per cent, if you do nothing at all, to at least 75 per cent, if you follow his methods.

"Lianyungang, a booming port city, has China's most extreme gender ratio for children under four: 163 boys for every 100 girls. These numbers don't seem terribly grim, but in ten years, the skewed sex ratio will pose a colossal challenge. By the time those children reach adulthood, their generation will have twenty-four million more men than women. The prognosis for China's neighbors is no less bleak: Asia now has 163 million females "missing" from its population. Gender imbalance reaches far beyond Asia, affecting Georgia, Eastern Europe, and cities in the U.S. where there are significant immigrant populations. The world, therefore, is becoming increasingly male, and this mismatch is likely to create profound social upheaval. Historically, eras in which there have been an excess of men have produced periods of violent conflict and instability. Mara Hvistendahl has written a stunning, impeccably-researched book that does not flinch from examining not only the consequences of the misbegotten policies of sex selection but Western complicity with them"--

Choosing Unsafe Sex focuses on the ways in which condom refusal and beliefs regarding HIV testing reflect women's hopes for their relationships and their desires to preserve status and self-esteem. Many of the inner-city women who participated in Dr. Sobo's research were seriously involved with one man, and they had heavy emotional and social investments in believing or maintaining that their partners were faithful to them. Uninvolved women had similarly heavy investments in their abilities to identify or choose potential partners who were HIV-negative. Women did not see themselves as being at risk for HIV infection, and so they saw no need for condoms. But they did recommend that other women, whom they saw as quite likely to be involved with sexually unfaithful men, use them.

The Arthur M. Sackler Colloquia of the National Academy of Sciences address scientific topics of broad and current interest, cutting across the boundaries of traditional disciplines. Each year, four or five such colloquia are scheduled, typically two days in length and international in scope. Colloquia are organized by a member of the Academy, often with the assistance of an organizing committee, and feature presentations by leading scientists in the field and discussions with a hundred or more researchers with an interest in the topic. Colloquia presentations are recorded and posted on the National Academy of Sciences Sackler colloquia website and published on CD-ROM. These Colloquia are made possible by a generous gift from Mrs. Jill Sackler, in memory of her husband, Arthur M. Sackler.

This practical guide shows readers a natural method of choosing the sex of a baby. It gives advice on health, diet, sperm count and ovulation in an easy-to-follow manner. The testimonies of numerous parents throughout the world reflects the success of the author's method.