To be clear before we start, "deformed" isn't exactly how I'd describe os acromiale, which is the condition you're describing. Very briefly, what happened to longbowmen (and current competitive archers, etc) was that the growing point (growth plate) on the scapula does not fuse with the bone itself; appearance of that in the left side seems to indicate that arm was taking strains consistent with holding a bow.
There's an interesting chapter on this in Fury (ed) The Social History of English Seamen, 1485-1649, concerning the archaeology of the Mary Rose.
This whole thing about the “deformed” skeletons of English longbowmen is a much repeated factoid that comes from a serious misunderstanding of anatomy and work-related remodeling of human skeletons.
The original work is a paper by Rhodes and Knusel in the American Journal of Physical Anthropology, in which they reported their findings on skeletons from a couple of medieval cemeteries in Towton and Fishergate in England. These skeletons belonged to two populations – archers using longbows, and infantry using swords and shields. They simply reported that it was possible to distinguish these two populations from their skeletons alone.
Specifically, they reported that:
"Many of these individuals may have participated to some degree in weapon-related training during the key juvenile development period, when bone is most responsive to phenotypic plasticity, yet there does not appear to be a single signature to indicate such training. This may relate to changes in training or technology through time or simply individual preference in weapons."
"The men of the Towton population appear to have been engaged in a habitual activity that preferentially loaded the left humerus when compared with the right. This disparity is strongest in the distal humeral shaft. The loading pattern varies such that it creates significant differences between limbs in diaphyseal shape from the mid-distal to midproximal shaft. These changes may relate to a type of weapon requiring both hands, possibly a longbow."
“The Fishergate blade-injured men appear to have been engaged in a habitual movement pattern that created right-side dominance in cross-sectional geometric properties. This is carried through all slice parameters and may relate to weapon use, most likely a right-handed, unimanual weapon."
This relatively innocuous conclusion, that there are skeletal differences between people using a two-handed weapon (“possibly a longbow”) and a one-handed weapon such as a sword, has been repeated often and grown in the telling, so now you hear it as “wow, these English bowmen used such powerful bows that their skeletons are deformed!” No, their skeletons are not deformed, it’s just that certain bones have adapted to their task of increased weight bearing, which happens to everyone who does any kind of repetitive physical activity over a period of time.
And yes, we find skeletal changes related to occupation in all kinds of warriors, ancient and modern. For example, here’s a paper about archers living 7,000 years ago in Sub-Saharan Africa with similarly remodeled skeletons:
And here’s the longbowmen paper by Rhodes I mentioned above:
There are dozens of similar examples from different periods and different times. It would be surprising if this were not the case.
Some pacific islanders had massive buildup of their OSS at the base of the skull, due to stone working, and also where the biceps connect. I know the ancient Chamorros of Guam had this regularly, and I believe the Tongans had it as well.
The Spartans did not practice weapon proficiency, so their skeletons do not show any deformities due to repeated forceful motion of a particular kind. Their physical training consisted of generic athletic exercises like running, discus-throwing and the like (and apparently they liked ball games).
Famously, the remains of 13 or 14 Spartans who died during the fighting in Piraeus in 403 BC have been found in a marked grave monument in the Kerameikos at Athens. There is nothing remarkable about the skeletons except the fact that one of them had a spearhead logded between the ribs, and another had several arrowheads stuck in his leg.
