Sex estimation from skeletal remains is crucial in forensic anthropology, with growing interest in the microscopic differences in bone structure between sexes. This study compared the Haversian canal (Osteonic canal) diameter (Diameter.Hc) and Haversian system (Osteon) diameter (Diameter.Hs) in the humerus, radius, and ulna of adult males and females in a Thai population. Transverse sections from the midshaft of each bone were obtained from 20 cadavers (10 males, 10 females), processed histologically, and stained with hematoxylin and eosin. Results showed no significant differences in Diameter.Hc and Diameter.Hs between sexes or among the three bones within each sex (p > 0.05). However, both parameters were larger in humans compared to Assamese macaques, highlighting interspecific variations in bone microstructure. These findings suggest that Haversian canal and system diameters may not be reliable sex indicators in the Thai population. Nonetheless, the observed differences between humans and non-human primates underscore the importance of further research into interspecific variation in bone microstructure and its potential applications in forensic anthropology and comparative anatomy.

KEY WORDS: Haversian system; Sexual dimorphism; Histomorphometry; Upper limb bones.