The morphology of the axillary border of the scapula with special reference to the Neandertal problem

Controversy· concern i ng· Neanderta� man·•s pl ace i n anatomi ca l ly modern man•s ancestry conti nues today , 1 20 years after the d i scovery of the fi rst Neandertal at Dusseldorf . The·major emphas i s of thi s controversy concerns the· cran i urn. In the· postcrani a· l materi a 1 , ·however , there are two areas wh4ch·eKh1bi t morphological · di fferences from modern man , al l other postcran i al features bei ng·with i n the ranges of vari a­ tion of modern man . These two·· different postcran i a l features are : the morphology of the· superior pubi c ramus of the i nnomi nate and the morphol ogy of the axi l l ary border of the scapul a . Th i s thes i s i s concerned wi th the l atter feature . Whi l e the axi l l ary borders of modern men common ly ·exhi bi t a ventral groove , . two-th i rds of the known Neandertal scapu l ae where the axi l l ary border i s preserved exh i bi t a dorsal groove . The rema i nder of those Neandertal scapu l ae where the axi l l ary border i s preserved exh i bi t a do ubl e sul cus , .or bi su l cate pattern . Thi s l atter type was fi rs t noted on the axi l l ary border of the Upper Pa l eol i th i c spec imen from Chancel ade . Th i s Chancel ade-type morpho l ogy occurs much more frequentl y i n Upper Pa l eol i th i c homi n i ds than i n modern popul ati ons . The ventra l or modern type i s· seen· i n· one Upper Pa l eol i thi c spec imen and has never been seen w· i th certa i nty among Neanderta 1 s . The purpo se of th i s thes i s i s to test hypotheses concern i ng.the changes on the axi l l ary borders of· scapul ae between· Neanderta l and modern man . Comparati ve materi al used i n thi s study was drawn from s kel e� tal materi a l of Ari kara Ameri can··I ndians.whjch -are ·housed i n the Osteol ogi. cal Laborator_y of .tbe Department of Anthropol ogy at the Un i vers.i ty of I Tennes see, Knoxvi l l e. i v v Correlations between various scapular axillary border morphologies with respect to age, sex and side were sought. Relationships between the various axillary border morphologies and .the angle of the glenoid fossa, . as well as· the.indeK,·of. ·.the-gleoo id fessa, .. were tested, but consistent correlations were not found. Positive correlations were found between· the robust· ic.;.ty· of· the· infraglenoid tubercles and . axillary border morphologies, as well as between border morphologies and associated humeral head indices and humeral head angles. · ·The results of this investigation suggest that the morphology of the axillary border of the scapula is a function of use. The . . . . . incidence of the Chancelade type is generally greater with advancing age and on the right side . This indicates ontogenetic causes for the f""'" varying . morphologies. Correlations between varying morphologies and. {/ humeral head indices and head/shaft angles indicate that�varying scapula­ humeral relationships influence the morphology of the axi· ·llary border of the scapula. In Neandertals,.the ba!'!! �:.��p��·�-�horax.app:����--� o {! have resulted in scapulohumeral musculoskeletal relati onships in (;I the . shoulder area which caul d have caused greater stress to be exerteci/ ( .! on the teres minor muscle, thus creating the dorsal groove on the axillary border of the scapula. It is suggested that the differences in morphological patterns on the axillary border of the scapula found between Neandertal and modern man can be functionally explained by (1) differences in the scapulohumeral relationship, and ( 2 ) greater biomechanical stress in the shoulder area of Neandertals than that of modern man due to the difference in cultural adaptations. 1