Isabel Scott and colleagues conducted a study of masculinity in men's faces across 12 populations varying in degree of economic development. They found that preferences for sex-specific facial traits only occurred in highly developed urban environments. Similarly, a study by Arslan Zaidi and colleagues found that while facial masculinity is correlated with adult height and growth, it is not correlated with immune gene diversity. Together, these results
A) provide evidence that women primarily choose males in order to gain indirect genetic benefits.
B) indicate that natural selection is stronger in urban environments than in rural environments.
C) support the hypothesis that masculine male facial traits are preferred by women because they indicate genetic quality.
D) challenge the idea that male facial traits have been under natural or sexual selection for a long time.