One of the biggest pet peeves of evolutionary biologists is when people try to find evolutionary explanations for every single human trait. Natural selection isn't 100% efficient, and many traits are there because of chance, because they're genetically linked to some other really desirable trait, or for myriad other reasons. That being said, wouldn't it be cool if baldness evolved to help men make more vitamin D from sunlight! (Spoiler alert: it didn't. But it does make men appear more dominant).
Does degree of baldness influence vitamin D status?
To determine the association, if any, between male-pattern hair loss (baldness) and serum 25-hydroxyvitamin D (25-OHD) levels.
DESIGN AND PARTICIPANTS:
A cross-sectional study of 296 healthy middle-aged and older men.
MAIN OUTCOME MEASURES:
Degree of baldness was independently assessed by two researchers using the Hamilton-Norwood scale and serum 25-OHD was measured in all men.
Classification of the degree of baldness by the two researchers showed a high level of agreement (kappa = 0.93). Forty-eight per cent of men had no hair loss or mild frontotemporal recession, 15% had predominant vertex loss, and 37% had significant scalp and vertex loss. After data were adjusted for potential confounding factors - including age, month of 25-OHD measurement, exercise levels, use of sunscreen, skin type and frequency of outdoor hat wearing - no significant differences in 25-OHD levels between these groups was detected (P = 0.60).
The degree of baldness does not appear to influence serum 25-OHD levels. The high prevalence of baldness in older men does not explain sex differences in 25-OHD levels. Other novel hypotheses are required to help determine whether baldness serves any physiological purpose."