Genital evolution: why are females still understudied?

Area of Science:

• Evolutionary biology
• Sexual selection
• Comparative anatomy

Background:

• Research on animal genitalia evolution has increased, but with a significant male bias.
• This bias has worsened since 2000, with historical focus on male genitalia over female counterparts.
• Previous critiques noted the oversight of female genitalia and physiology in evolutionary studies.

Purpose of the Study:

• To analyze the trend and extent of male bias in animal genitalia research.
• To investigate factors contributing to this bias across different subdisciplines and taxonomic groups.
• To highlight the impact of this bias on understanding genital evolution and coevolutionary dynamics.

Main Methods:

• Literature analysis of studies on animal genitalia evolution.
• Categorization of studies by subdiscipline (e.g., lock-and-key hypothesis, cryptic female choice) and taxonomic group.
• Assessment of bias trends over time and correlation with study accessibility.

Main Results:

• A persistent and worsening male bias in the study of animal genitalia evolution was confirmed.
• The degree of bias varied, with 'lock-and-key' studies showing the highest male focus and 'cryptic female choice' studies including both sexes.
• Bias did not correlate with the ease of studying male versus female genital characteristics.

Conclusions:

• The male bias in genitalia evolution research is not solely due to anatomical accessibility but reflects outdated assumptions about sexual roles.
• Recent research demonstrates rapid evolution of female genital traits and complex male-female coevolutionary dynamics.
• Overcoming this single-sex bias is crucial for a comprehensive understanding of genital evolution.