3 published verifications about Thermal Stress Thermal Stress ×
“In males living in the Kalahari environment, elevated circulating testosterone indicates that a sexual-selection-related physiological axis remains active in the population despite thermal stressors.”
The claim is not supported by the cited evidence. The only directly relevant study of desert-dwelling human males does not show elevated testosterone, and the broader heat-stress literature mostly points in the opposite direction: thermal stress tends to suppress testosterone and impair reproductive physiology. The inference to an active sexual-selection-related axis in Kalahari males is therefore unproven.
“Sexual dimorphism is energetically costly to produce and maintain, and these costs are expected to increase as environments become more thermally stressful.”
The central claim is supported, but it is broader than the strongest evidence. Many sexually dimorphic traits do carry energetic costs, and thermal stress generally increases metabolic strain in ways that can raise those costs. Still, the evidence is strongest for specific traits and species, and some studies show warming can reduce dimorphism through energy reallocation rather than only increasing trait-maintenance costs.
“Under thermal stress, elevated cortisol can reduce testosterone levels, affecting sexually dimorphic traits.”
The evidence supports the claim in broad terms. Heat or thermal stress can be associated with higher cortisol and lower testosterone, and glucocorticoids are well documented to suppress testosterone production. The main caveat is that heat can also lower testosterone through other pathways, so cortisol is a plausible mechanism, not always the sole or primary one; effects on sexually dimorphic traits are better supported for sustained hormone changes than for short-term stress.