Wednesday, March 7, 2012

Evolution of Fingers


Which appendages actually differentiate humans from other species? If I were to choose top three most important body parts of the human body, I would definitely choose fingers as one of them. We all know that fingers immensely widen our ability to use tools, perform acute tasks, communicate through sign and body languages, and many more functionalities. Not only do they aid us in daily activities, but also gives us enormous advantages in terms of minuscule and detailed controls.

The most fundamental question that we can ask ourselves is this: why are fingers important, except for the function of making others mad by flipping them? Human fingers are designed so that they are ideal for throwing and clubbing positions. Evolutionarily, the action of “throwing” and “gripping” would have been very important for survival, whether they were throwing spears or rocks, clubbing with wooden sticks, or even holding tools firmly when crafting weapons. These unique features can be found in baseball: pitchers can throw round balls, and batters can swing their bats, all due to our finger structures.



Fig 1. Standard baseball grip.




As we can see from the picture, we would not be able to throw a baseball without our firm thumb. These two types of grips, holding spherical objects or grabbing sticks, make us humans.


Fig 2. Different grips that human fingers can perform.




So do any other species have fingers? Yes! One of the prime examples of organisms with clear finger structures is chimpanzee. The biggest difference between chimpanzee fingers and human fingers is the length: while human thumbs are much longer, the other four fingers of chimpanzees are much longer. The chimpanzees’ elongated metacarpal bones can be explained by their knuckle-walking, where they require much more robust fingers.




Fig. 3 The hand located on the left side represents chimpanzee's hand; on the right represents human's hand. As we can clearly see, chimpanzees have longer fingers except for the thumb. 




These longer fingers help the function of “hook grips” as well, used when grabbing onto tree branches. The human thumb, however, is used when performing a “forward grip,” which is similar to when holding a kendo sword in front of you. Without a sturdy thumb, this motion would be impossible; without this motion, using weaponry that requires swinging clubs would be impossible.



Fig 4. Our friendly Pokemon #151, Mewtwo, with three fingers.


Why do we have five fingers? Why not three like our Pokemon friend, Mewtwo? No one really knows. The scientific term for having five digits is called pentadactyly. In nature, we can seldom find polydactyly, meaning more than 5 digits. The most popular example is the panda:

Fig 5. Panda's palm structure with 6 fingers.




Presently, no one can assuredly explain this natural phenomenon. Does having more digits create better support system for bigger, heavier animals, like panda? Does it spread out partial pressures along each finger? Does more fingers mean more claws to attack the prey? No one knows.

To sum up, fingers and dexterity give human beings the uniqueness and advantage. Let’s be grateful for our fingers, and stop using them for this:

Jk. 




Sources used:

1. Young, W. Richard. "Evolution of Human Hand: the Role of Throwing and Clubbing." Journal of Anatomy, 24 Jan 2003 <http://onlinelibrary.wiley.com/doi/10.1046/j.1469-7580.2003.00144.x/full>
2. "Fish with Fingers." Houston PBS. Evolution Home 2011 <http://www.pbs.org/wgbh/evolution/library/03/4/l_034_03.html>

Some blogs:
3. http://fishfeet2007.blogspot.com/2007/05/life-on-land-evolution-of-five-fingers.html
4. http://www.athro.com/evo/pthumb.html

3 comments:

  1. You mentioned that the longer fingers in chimpanzees allow them to to have a hook grip and that the human thumb allows us to have a forward grip. But can't chimpanzees also use a forward grip? Does the shorter thumb make it less useful?

    -Rebecca Searle

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  2. Hey Rebecca, thank you for your comment. Yes, the thumb allows us to tilt the item that we're grabbing forward, and to pull it back after striking downwards (or sideways). Chimpanzees' long fingers allow them to hook onto branches that gives them more surface area to wrap around the branches, but they do not have long, strong thumbs to support such forward grip motions.

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  3. The pictures are great, but everyone should at some point experience chimp hands close up. On a recent trip to the Houston Zoo, I was quite surprised to see how similar the chimp's hands look to mines, and this was with me standing about 2 feet away from the chimp having only a glass wall between us. It was quite a sight!

    --Rachael Morris

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