Hi. I have very straight thumbs. I've also not seen anyone else with such straight thumbs, until you! I've read that bendy thumbs, in which the last segment bends backwards ("Hitchhiker's Thumb"), is a recessive trait & about 1/3 of people show it (have thumbs that bend backwards). But I haven't found anything about the genetics of thumbs like ours—the usual thumb appears to curve a little bit backwards at the end. Even odder, I have joint hypermobility (and EDS—a disorder of weak collagen that affects the whole body), yet my thumbs are super non-bendy. Is is something to do with way the joint is constructed that limits backwards motion?