Conclusion
Here, we provide mechanistic evidence that gelada chest redness is
linked to increased blood flow near the surface of the skin,
specifically through increased blood vessel branching in the chest skin
in males. Although we did not detect a sex difference in chest skin gene
expression related to androgen and estrogen regulation, future research
into the correlation between fluctuations in fecal testosterone
metabolites and chest redness within males will help determine whether
another aspect of hormonal regulation is involved in chest redness
signaling. Going forward, we hope to better understand whether increased
angiogenesis creates a current-condition signal for males in the cold,
high-altitude environment of the Ethiopian highlands by leveraging
biomarkers of energy balance or heat loss.