An electromyographic study of the pectoralis major in Atelines and Hylobates , with special reference to the Evolution of a pars clavicularis

Bibliographic Data

ID8315985
AuthorsJack T Stern (State University of New York), James P Wells (State University of New York), William L Jungers (0000-0002-8092-1429, State University of New York), Andrea K Vangor (State University of New York), J G Fleagle (0000-0003-3162-808X, State University of New York)
Year1980
Volume52
Issue1
Pages13-25
Publication date1980-01-01
Peer ReviewedYes
Open AccessYes
TypeARTICLE
VenueAmerican Journal of Physical Anthropology (JOURNAL)
Journal identifiersISSN: 0002-9483 • E-ISSN: 1096-8644
PublisherWiley (PUBLISHER • GB)
DOI10.1002/ajpa.1330520104
PMID6768302
OpenAlexW2075254491
LanguageEN
Citations received35
References cited10

Among primates there is striking variation in the extent of the origin of pectoralis major from the clavicle. A significant clavicular attachment (pars clavicularis) occurs only in Alouatta, Lagothrix, Hylobates, Pan (troglodytes, paniscus and gorilla ), and Homo . Interpreting this trait in nonhuman primates as an adaptation to frequent use of a mobile forelimb in climbing and suspension is contraindicated by the absence of a clavicular origin in Ateles and Pongo . We have undertaken a telemetered electromyographic study to determine any special role of the most cranial part of the pectoralis major in comparison to its caudal part, and to the deltoid, during vertical climbing, pronograde quadrupedalism, and armswinging in Ateles, Lagothrix, Alouatta , and Hylobates . The results show that the cranial pectoralis major possesses a role not shared by the caudal fibers: initiation of the recovery phase of the locomotor cycle . When ability to execute rapid or powerful recovery of the adducted forelimb is required in an animal with a shoulder joint lying on a plane cranial to that of the manubrium, the movement will be facilitated if the origin of the pectoralis major is extended onto the clavicle. Such is the case in nonhuman primates possessing this trait. The absence of a clavicular origin in Ateles and Pongo may be related to diminished selective pressures to perfect locomotor modes such as pronograde quadrupedalism, armswinging, or climbing thick vertical trunks, that demand rapid or powerful recovery of the adducted forelimb. If the arboreal ancestor of humans had evolved a clavicular origin of pectoralis major, this animal would be preadapted for certain uses of the forelimb in its bipedal descendant

Arboreal locomotion · Biology · Clavicle · Forelimb · Gorilla · Humerus · Hylobates · Pan paniscus · Pongo pygmaeus · Postcrania · Quadrupedalism · Scapula · Zoology · Anatomy · Animal Vocal Communication and Behavior · Hemispheric Asymmetry in Neuroscience · Primate Behavior and Ecology

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