PURPOSE To identify anatomical differences in the deltoid tuberosity of Homo sapiens and Pan troglodytes, potentially relating to the different uses of the forelimb in these two phylogenetically related species. BASIC PROCEDURES We have used three-dimensional geometric morphometrics (3D GM) to analyze the deltoid tuberosity of scanned humeri from 30 H. sapiens and 27 P. troglodytes. We also used the 3D scans of the humeri to calculate the surface area of the deltoid tuberosity. Finally, we dissected the deltoid muscles of three H. sapiens and three P. troglodytes to determine the relative mass and the physiological cross-sectional area (PCSA) of each part of the muscle. MAIN FINDINGS The 3D GM analysis of the deltoid tuberosity identified an anteroposterior enlargement of the P. troglodytes tuberosity, with a lateral displacement of the middle segment, whereas in H. sapiens, there was a distal displacement of the middle segment. Muscle architecture analysis indicated higher normalized values of the PCSA of the clavicular and acromial deltoid in P. troglodytes. PRINCIPAL CONCLUSIONS The anatomical features observed in our P. troglodytes specimens serve to strengthen the three parts of the deltoid muscle. This fact can be related to the use of the forelimb in locomotion, both arboreal and knuckle-walking, in this species. Humans use the forelimb mainly in manipulative tasks, so they do not develop - as do chimpanzees - the anatomical features that increase the deltoid force. Our findings have shown that the different uses of the forelimb in modern humans and common chimpanzees can affect both muscle architecture and bone morphology, either jointly or separately.

中文翻译：

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现代人（智人）和黑猩猩（盘尾猿）的三角肌结节的定量形状分析。

目的鉴定智人和盘状穴居人的三角肌结节的解剖学差异，这可能与这两个系统发育相关物种中前肢的不同用途有关。基本程序我们已使用三维几何形态计量学（3D GM）分析了来自30个智人和27个穴居人的腐殖质的三角肌结节。我们还使用了肱骨的3D扫描来计算三角肌结节的表面积。最后，我们解剖了三个智人和三个穴居人的三角肌，以确定肌肉各部分的相对质量和生理截面积（PCSA）。主要发现三角肌结节的3D GM分析确定了穴居假单胞菌结节的前后扩大，中间段有侧向移位，而在智人中，中间段有远侧移位。肌肉结构分析表明，穴居假单胞菌的锁骨和肩峰三角肌PCSA的标准化值较高。主要结论在我们的穴居人标本中观察到的解剖学特征有助于加强三角肌的三个部分。这个事实可能与在该物种的树木运动和指关节行走中使用前肢有关。人类主要在操纵任务中使用前肢，因此他们不会像黑猩猩那样发育会增加三角肌力量的解剖特征。我们的发现表明，在现代人类和常见的黑猩猩中，前肢的不同用法会影响肌肉的结构和骨骼的形态，