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I noticed that in my hand the index and middle finger are aligned in one direction and the next two fingers somewhat in the opposite direction. My question is, why are our fingers aligned in that way? Moreover, is it of any evolutionary significance?

For clarity, I am posting a picture of my hand.hand

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    $\begingroup$ I think (and only think) its more about physics than biology. Fingers are thick at bottom and thin at top, so all fingers make an angle with others when joined together. Also, if you have a look at anatomy of hand, you might get your answer (like i1.wp.com/scghed.com/wp-content/uploads/2013/12/… or visualdictionaryonline.com/images/human-being/anatomy/skeleton/…) $\endgroup$ – another 'Homo sapien' Mar 25 '16 at 10:31
  • $\begingroup$ @another'Homosapien' Even if you separate all the fingers, they still seem to bend in one direction(try it). So, I don't think it has anything to do with the angle between the fingers. Also, the images too don't explain much about the orientation even as they show that the fingers ARE oriented. $\endgroup$ – ajitanshu singh Mar 25 '16 at 10:36
  • $\begingroup$ Please elaborate what you mean by 'bend in one direction'. I don't think that I really did get you on this. $\endgroup$ – another 'Homo sapien' Mar 25 '16 at 10:44
  • $\begingroup$ @another'Homosapien' What I mean is, when the fingers are separated i.e. kept at some distance from each other the apex of the index and middle finger seems to be slightly bent in the left direction as seen in the image. $\endgroup$ – ajitanshu singh Mar 25 '16 at 10:49
  • $\begingroup$ Okay, this doesn't seem to have evolutionary advantage. I mean, just think of a work which a person with "index and middle finger slightly bent in the left direction" can do better than person without it, and which would provide substantial benefit to person with "index and middle finger slightly bent in the left direction" ;) $\endgroup$ – another 'Homo sapien' Mar 25 '16 at 10:53
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This is normal, and the effect is accentuated dramatically if you pretend to be holding an imaginary round object (somewhat smaller than a baseball, for instance.) The fingertips will all approximately point towards the very end of the thumb.

enter image description here

(See upper right image.) If the stone were smaller, the effect would be more visible.)

This orientation of the fingers makes the hand and fingers extremely versatile, being able to grasp and manipulate objects of a wide variety of shapes.

It also allows fine manipulation of thumb and fingers. Touching each fingertip to the tip of the thumb quickly shows the same effect - the fingertips approximately align with the thumb. If they didn't align this way, we would lose some of our very fine (as in requiring great precision, not as in quality) motor skills.

I'm not going to hypothesize on why the hand evolved the way it did; it's very efficient and that seems reason enough.

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    $\begingroup$ Is it always the case? Do all people have this kind of hand structure? Are there any studies that say so? $\endgroup$ – WYSIWYG Mar 26 '16 at 13:27
  • $\begingroup$ @WYSIWYG - This is, as I said, "normal". I'm sure it's in an anatomy textbook someplace. Does it sound wrong to you? $\endgroup$ – anongoodnurse Mar 26 '16 at 14:21
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    $\begingroup$ No. The theory sounds quite plausible but I haven't come across any text that actually pinpoints the morphology in this fine detail. I could find these two articles: 1 and 2, when I searched but I cannot find either of them specifying this. Can you please cite a reference as this does to seem quite obvious to me (and probably other readers)? $\endgroup$ – WYSIWYG Mar 26 '16 at 14:36
  • $\begingroup$ @WYSIWYG - I haven't had a good anatomy textbook since mine was stolen on one of my surgery rotations. I was taught this by surgeons (including orthopedists) who work with their hands for a living. They were probably wrong, because they didn't cite a source for me, either. So feel free to remove for lack of a source. $\endgroup$ – anongoodnurse Mar 26 '16 at 21:42
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Observation: The bend in the fingers gives the straight hand a more compact appearance so that we can actually tightly close the gaps between the fingers.

Hypothesis: Without the bend small gaps would remain between the tip and the first joint of the fingers unless we press the fingers together with force. Not having this gap could protect the fingers from injury while walking or running through tight underbrush because the likelyhood of entangling the fingers in some vine or branch is lower. Also, being able to compact the hand may help us to easier scoop up water with our hands.

(yes my hand show the same slight bend in the fingers)

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  • $\begingroup$ Could you elaborate on the part 'not having this gap.....likelihood of entangling the fingers in some vine or branch is lower' ? $\endgroup$ – ajitanshu singh Mar 26 '16 at 1:29
  • $\begingroup$ well, its like the difference between running a comb and a ruler through your hair, which is more likely to get entangled? $\endgroup$ – Thawn Mar 27 '16 at 13:43

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