Osteology Everywhere: Head for the hills

Last week I was exploring central England with the brilliant Jess Beck, an archaeology PhD student at the University of Michigan. Both of us avid (nay, rabid) connoisseurs of everything skeletal, we espied the likes of a specific human bone in the scenic landscape of the the Cotswolds. Check out JB’s blog, Bone Broke, for her take on this geographical/geological/skeletal formation (as well as for lots of killer osteology and bioarchaeology tips and tricks). Do it now! NOW!

After you’ve checked out her site, behold this sight – what bone is lurking in the landscape?

osteourrywhere Cotswolds

As with Rorschach inkblots, probably lots of bones could be seen in this image. But what Jess & I saw was a hamate, the greener hue hewn into the hills, whose sizeable hamulus runs from the bottom right to join the rest of the carpal around the center of the image. Here’s what a real hamate looks like:

hamate

Top: Human hamate from Human Osteology (White, Black & Folkens, 2012). Bottom: rough anatomical position of the hamate in the human wrist.

The hamulus of the hamate is an attachment point for the flexor retinaculum, the band of fascia stretching across your wrist to hold your extrinsic digital flexor muscles (or rather, their tendons) in place; you could think of it as the bridge covering the carpal tunnel. Now, comparing the grassy hamulus with an actual human one, you’ll spot two important differences: first, the grassy one isn’t blunt like the humans’, but ends in a long point. Oops! Just pretend it’s rounded off. Second, the grassy hamulus is huge relative to the overall size of the bone (or valley) compared with the human form. The size of the hamulus partially reflects the size of the carpal tunnel: chimpanzees, with powerful wrists and forearms, have long hamuli.

A huge nerd, I didn’t just see any hamate in this Cotswold vale. I also immediately thought of KNM-WT 22944, an Australopithecus afarensis hamate from the 3.5 million year old site of South Turkwel in Kenya (Ward et al., 1997):

WT 22944-Ward &al 1997

From Ward et al., 1999. Sorry it’s not in the same orientation as the above image. Hamulus is the projection pointing to the bottom left corner of the “medial” image.

An absolutely and relatively massive hamulus in WT 22944 suggests whoever this bone belonged to had some powerful gripping capabilities, while a geologically younger A. afarensis hamate from Hadar (AL 333-50) had a smaller, more human-like hamulus. Maybe (some) A. afarensis were still using their arms a lot for tree-climbing, in spite of being more than capable bipeds (I’ve talked about this before here)….

One final thought: People do like the way she says, “hamate.”

Ward et al., 1999. South Turkwel: a new pliocene hominid site in Kenya. Journal of Human Evolution 36: 69-95. link

White et al., 2012. Human Osteology 3rd Edition. link

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