Foreword to the English Translation of the 4th EditionForeword to the 1st German EditionIntroductionWomen and some Men against NaturalnessHistory and Topicality: Simone de Beauvoir and Judith ButlerWhy considering »Naturalness«?Contra »Naturalness« - Emancipatory Arguing for the Education of WomenDifferences as the Product of Society:The Human Being as a Social OnePoverty and Limiting Recent Gender Research to the Privileged ClassesThe Human Being as a Social OneEvolutionary Thinking and its Potential for Social ChangeHistorical Biological Theories of Sex - Theories of Two or More SexesToo Simplistic: The Current State of Research in Gender StudiesConcerning the Biological Theories of the SexesAntiquity - The »One-Sex« and »Two-Sex« ModelsThe Middle-Ages - Not Just Reducing but CreativeHumorism and the Theory of the TemperamentsTheories of Preformation in the Seventeenth Century - Describing Differences of the SexesThe Transition to the Developmental Concept (Epigenesis) - Descriptions of Sameness May Tie In Analogy and Sameness, as Tied in With Developmental TheoriesHuman Beings are Paired in Themselves - Being Adult »Female-Males« and »Male-Females«»Activity«, »Advancement«, »Lag« - Descriptions of the Differences of the Sexes Which Tie in with Developmental TheoriesDetailed Descriptions of Differences»Newer« Evolutionary Theories After Charles Dawin - Differences of the Sexes and Emancipatory »Romanticizing Darwin«ConclusionsCurrent Biological Theories of the SexesThe Sexes between Brain, Muscles, and Microscopic ParticlesProcreation as a Characteristic of the Species - and the Individual Form of Human GenitaliaThe Formation of the Genitalia in the Development of the EmbryoGonads, Germ Cells and Eventually Chromosomes and Genes: Do They Prove Sexual Binarity?Development and Differentiation: The Transition to Process Orientation in Current Theories of the Development of the SexesConclusionsClosingQuoted and Recommended (*) Literature