That was one of my thoughts too.
I would guess that these may be palm wood, or even peeled moon-&-star seeds. (As from a Buddhist mala.)
However, if they are much harder than a woody seed, the material might be fossilized palm wood (or similar)—such as was exploited for making pumtek beads.
Nevertheless, I would not rule-out bone as a possible material. I can see some evidence of a crust on one bead that suggests bone—but could also be the remaining surface of a seed.
JDA.
