2 published verifications about Sexual Selection Sexual Selection ×
“Physiological costs of expressing sexually selected traits (including elevated thermal loads) can oppose natural selection that would otherwise favor smaller or less ornamented phenotypes, especially under environmental stress.”
The evidence strongly supports stress-amplified costs of sexually selected traits, but the claim states the mechanism inaccurately. Physiological and thermal costs of ornaments usually strengthen natural selection for smaller or less ornamented phenotypes; it is sexual selection favoring exaggerated traits that opposes that pressure. Environmental stress often magnifies these costs, though some taxa show compensatory heat tolerance.
“Testosterone is the principal endocrine mechanism by which sexual selection translates into morphological sexual dimorphism.”
Testosterone is an important driver of many male-typical sexually selected traits, but the evidence does not support it as the general principal endocrine mechanism for morphological sexual dimorphism overall. Across taxa and traits, dimorphism also depends on estrogens, ovarian regulation, growth pathways, and sex-linked developmental effects. The claim overstates testosterone’s scope and exclusivity.