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The second and third editions of the Dungeons and Dragons role-playing game featured a humanoid race (named an Arcane in 2nd edition and a Mercane in later editions) with a particular anatomical quirk, namely the fingers on their hands each had an extra joint- that is to say unlike humans their thumbs each had three joints and each of the other fingers had four.
Are there any obvious benefits or drawbacks to this anatomical arraignment that come to mind?
One of the weaknesses of our hands is that the fingers are short for heavy gripping tasks. We can't wrap our hands around a branch over a certain diameter without our body weight tearing our fingers open. Longer fingers would allow us to grasp higher diameter objects and lift them or ourselves. We currently cannot bring our whole strength to bear on some gripped objects over a couple of inches diameter.
So a strongman back in the day made a dumbbell no one except he could lift until recently. So far only 2 people have managed it in 100 years. The handle was too fat and although the weight was fine for most strongmen, they just couldn't grasp it and hold on while lifting.
If your extra joint also increases the length it may have the same effect which would translate into increased dexterity with many objects that require grip strength like weapons etc,.
They wouldn't be (as) affected by the pullup bar scam.
Besides being able to wrap around handles that are too fat, the extra joint also allows you to hold on better when things rotate or spin after being gripped.
Note that an extra joint probably also implies much more flexibility in the wrist joint - otherwise you just end up breaking your wrist more frequently.
