This study aims to provide an overview of the distribution of the Spanish scientific workforce focusing on differences in authorship position by gender, academic age, number of authors, and research field. The results show some degree of parity in younger age cohorts and areas such as biomedicine, but little participation of females in the oldest age cohort and areas such as mathematics. In addition, the presence of women undergoes significant changes in certain areas and decreases in oldest age cohorts. This circumstance leads to a low probability of finding women or junior researchers in relevant authorship positions. Policymakers should know that inequalities in the scientific workforce must be considered when addressing/proposing scientific evaluation criteria.