Digit Ratio: A Pointer to Fertility, Behavior, and Health (A volume in the Rutgers Series in Human Evolution, edited by Robert Trivers.)

Could the length of your fingers indicate a predisposition to breast cancer? Or musical genius? Or homosexuality? In Digit Ratio, John T. Manning posits that relative lengths of the second and fourth digits in humans (2D:4D ratio) does provide such a window into hormone- and sex-related traits.It has been known for more than a century that men and women tend to differ in the relative lengths of their index (2D) and ring (4D) fingers, which upon casual observation seem fairly symmetrical. Men on average have fourth digits longer than their second digits, while women typically have the opposite. Digit ratios are unique in that they are fixed before birth, while other sexually dimorphic variables are fixed after puberty, and the same genes that control for finger length also control the development of the sex organs. The 2D:4D ratio is the only prenatal sexually dimorphic trait that measurably explains conditions linking testosterone, estrogen, and human development; the study of the ratio broadens our view of human ability, talent, behavior, disposition, health, and fertility. In this book, Manning presents evidence for how 2D:4D correlates with traits ranging from sperm counts, family size, musical genius, and sporting prowess, to autism, depression, homosexuality, heart attacks, and breast cancer, traits that are all linked with early exposure to sex hormones. This new series presents innovative titles pertaining to human origins, evolution, and behavior from a multi-disciplinary perspective. Subject areas include but are not limited to biological and physical anthropology, prehistoric archaeology, evolutionary psychology, behavioral ecology, and evolutionary biology. The series volumes will be of interest primarily to students and scholars in these fields.Could the length of your fingers predict a predisposition to breast cancer? Or musical genius? Or homosexuality? In Digit Ratio, John T. Manning posits that relative lengths of the second and fourth digits in humans (2D:4D ratio) does provide such a window into fertility-and sex-related traits.It has been known for more than a century that men and women tend to differ in the relative lengths of their index and ring fingers, which upon casual observation seem fairly symmetrical. Men on average have fourth digits longer than their second digits, while women typically have the opposite. Digit ratios are unique in that they are fixed before birth, while other sexually dimorphic variables are fixed after puberty, and the same genes that control for finger length also control the development of the sex organs. The 2D:4D ratio is the only prenatal sexually dimorphic trait that measurably explains conditions linking testosterone, estrogen, and human development; the study of the ratio broadens our view of human ability, talent, behavior, disposition, health, and fertility. In this book, Manning presents evidence for how 2D:4D correlates with genetic traits ranging from sperm counts, the likelihood of having male versus female offspring, musical genius, and sporting prowess, to autism,depression, homosexuality, heart attacks, or breast cancer, traits that are all linked to sex hormones.

Could the length of your fingers indicate a predisposition to breast cancer? Or musical genius? Or homosexuality? In Digit Ratio, John T. Manning posits that relative lengths of the second and fourth digits in humans (2D:4D ratio) does provide such a window into hormone- and sex-related traits.

It has been known for more than a century that men and women tend to differ in the relative lengths of their index (2D) and ring (4D) fingers, which upon casual observation seem fairly symmetrical. Men on average have fourth digits longer than their second digits, while women typically have the opposite. Digit ratios are unique in that they are fixed before birth, while other sexually dimorphic variables are fixed after puberty, and the same genes that control for finger length also control the development of the sex organs. The 2D:4D ratio is the only prenatal sexually dimorphic trait that measurably explains conditions linking testosterone, estrogen, and human development; the study of the ratio broadens our view of human ability, talent, behavior, disposition, health, and fertility. In this book, Manning presents evidence for how 2D:4D correlates with traits ranging from sperm counts, family size, musical genius, and sporting prowess, to autism, depression, homosexuality, heart attacks, and breast cancer, traits that are all linked with early exposure to sex hormones.

Could the length of your fingers indicate a predisposition to breast cancer? Or musical genius? Or homosexuality? In Digit Ratio, John T. Manning posits that relative lengths of the second and fourth digits in humans (2 ratio) does provide such a window into hormone- and sex-related traits. It has been known for more than a century that men and women tend to differ in the relative lengths of their index (2D) and ring (4D) fingers, which upon casual observation seem fairly symmetrical. Men on average have fourth digits longer than their second digits, while women typically have the opposite. Digit ratios are unique in that they are fixed before birth, while other sexually dimorphic variables are fixed after puberty, and the same genes that control for finger length also control the development of the sex organs. The 2 ratio is the only prenatal sexually dimorphic trait that measurably explains conditions linking testosterone, estrogen, and human development; the study of the ratio broadens our view of human ability, talent, behavior, disposition, health, and fertility. In this book, Manning presents evidence for how 2 correlates with traits ranging from sperm counts, family size, musical genius, and sporting prowess, to autism, depression, homosexuality, heart attacks, and breast cancer, traits that are all linked with early exposure to sex hormones. Figures......Page 10 Preface and Acknowledgments......Page 14 Tables......Page 12 CHAPTER 1 Sex and Population Differences......Page 20 CHAPTER 2 Associations with Testosterone and Estrogen......Page 43 CHAPTER 3 Assertiveness, Status, Aggression, Attractiveness, and the Wearing of Rings......Page 60 CHAPTER 4 Reproductive Success and Sexually Antagonistic Genes......Page 72 CHAPTER 5 Hand Preference, Verbal Fluency, Autism, and Depression......Page 81 CHAPTER 6 Birth Weight, Heart Attack, Breast Cancer, and Sex-Dependent Diseases......Page 95 CHAPTER 7 Male and Female Homosexuality......Page 119 CHAPTER 8 Music, Musicians, and Mate Choice......Page 134 CHAPTER 9 Sporting Ability, Running Speed, Spatial Perception, Football Players, and Male Competition......Page 145 CHAPTER 10 2nd to 4th Digit Ratio and Future Research......Page 160 Bibliography......Page 166 Index......Page 184 Sex And Population Differences -- Associations With Testosterone And Estrogen -- Assertiveness, Status, Aggression, Attractiveness, And The Wearing Of Rings -- Reproductive Success And Sexually Antagonistic Genes -- Hand Preference, Verbal Fluency, Autism, And Depression -- Birth Weight, Heart Attack, Breast Cancer, And Sex-dependent Diseases -- Male And Female Homosexuality -- Music, Musicians, And Mate Choice -- Sporting Ability, Running Speed, Spatial Perception, Football Players, And Male Competition -- 2nd To 4th Digit Ratio And Future Research. John T. Manning. Includes Bibliographical References (p. 147-164) And Index. Could the length of your fingers predict a predisposition to breast cancer? Or musical genius? The author posits that relative lengths of the second and fourth digits in humans provides a window into fertility- and sex-related traits