title: Supernumerary heads to biceps brachii muscle and Asian population history.
abstract: Supernumerary heads of biceps brachii are one of the most common anatomic variants in the muscular system and appear to develop under genetic control and vary in prevalence among populations. Variation in prevalence and morphology therefore has the potential to contribute to understanding of human population history. Until now, there has been no publication of the prevalence of the variant in Southeast Asian populations. The aim of this research is to document the prevalence and morphology of the variant in a sample of Thai cadavers and to consider the significance of the findings. The method used was dissection of arms of 162 donated cadavers at Khon Kaen University, Thailand. The sample showed high prevalence of third heads of biceps brachii in 35% of cadavers, compared with the prevalence of up to 25% reported in large samples worldwide. The sample also showed equal prevalence in males and females and one-third present bilaterally. This pattern is similar to that found in East Asia, and very different from the low prevalence found in South Asia. The morphology of the supernumerary heads does not appear to be different from elsewhere in the world based on the minimal comparable data available in the literature. The Southeast-East Asian pattern of prevalence is consistent with current theories of population history in the region and suggests anatomical variation of the postcranial soft tissues may ultimately contribute to understanding of past human migrations.
authors.affiliation: Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand. Electronic address: nawtec@kku.ac.th.
authors.forename: N
authors.initials: N
authors.lastname: Techataweewan
authors.affiliation: Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.
authors.forename: Y
authors.initials: Y
authors.lastname: Toomsan
authors.affiliation: College of Medicine and Public Health, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand.
authors.forename: C
authors.initials: C
authors.lastname: Maneenin
authors.affiliation: Department of Epidemiology, Faculty of Public Health, Khon Kaen University, Khon Kaen 40002, Thailand.
authors.forename: N
authors.initials: N
authors.lastname: Tungsrithong
authors.affiliation: Department of Anatomy, Otago School of Medical Sciences, University of Otago, Dunedin 9054, New Zealand.
authors.forename: N
authors.initials: N
authors.lastname: Tayles
mesh_terms: D000328:Adult; D001132:Arm; D044466:Asian People; D002102:Cadaver; D005260:Female; D063426:Human Migration; D006801:Humans; D006811:Humerus / Q000033:anatomy & histology; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000294:innervation; D013785:Thailand
keywords: Asian migration; Cadaver dissection; Muscular variants; Thailand