Book excerpt: Manning (biological sciences, University of Liverpool) argues that the relative lengths of the second and fourth fingers are genetically linked to hormone- and sex-related traits, and by extension with sperm counts, family size, musical genius, sporting prowess, autism, depression, homosexuality, heart problems, and breast cancer. He suggests that the study of the ratio between the lengths of the second and fourth finger can broaden our understanding of human ability, behavior, and health. Three photographs, 38 figures, and eight tables are included. Annotation copyrighted by Book News Inc., Portland, OR.