Unique compared with recent and prehistoric Homo sapiens,
Neandertal humeri are characterised by a pronounced right-
dominant bilateral strength asymmetry and an anteroposteriorly
strengthened diaphyseal shape. Remodeling in response to
asymmetric forces imposed during regular underhanded spear
thrusting is the most influential explanatory hypothesis. The
core tenet of the “Spear Thrusting Hypothesis”, that underhand
thrusting requires greater muscle activity on the right side of
the body compared to the left, remains untested. It is unclear
whether alternative subsistence behaviours, such as hide
processing, might better explain this morphology. To test this,
electromyography was used to measure muscle activity at the
primary movers of the humerus (pectoralis major (PM), anterior
(AD) and posterior deltoid (PD)) during three distinct spear-
thrusting tasks and four separate scraping tasks. Contrary to
predictions, maximum muscle activity (MAX) and total muscle
activity (TOT) were significantly higher (all valu