Sonia Doshi soniadoshi7@gmail.com
Saturday, April 2, 2011
A Knee-Slapper!
Shubin describes the human body as a "dressed-up" fish as compared to a "hot-rod Beetle" (185). The consequences of evolution are clear in looking at our own bodies. We have the capabilities of walking on two legs, talking, and incredible dexterity in our fingers and toes, but we are still susceptible to "everything from hemorrhoids to cancer" (185). As an example, Shubin brings up the "unhappy triad" in the knee because the three structures making up the knee (medial meniscus, medial colateral ligament, and anterior cruciate ligament), are very common to injury (185). In relation to structure and function, how could the knee be better-structured in order to become less common to injury? What are the barriers that are stopping us from becoming the "perfect mammal"? Even going into our vulnerability of different diseases, what are some causes of being infected by diseases, and what are our defense mechanisms as of now?
Subscribe to:
Post Comments (Atom)
Recently, there have been many theories on how the human knee could be better structured. Ideas such as using a pivot joint (like the elbow) and having the knee completely turned around like a horse leg have been mentioned. But what is the point of talking about “better knee designs” if there is no way for us to change them. Evolution happens over time as we all know (millions of years in fact) so there is really no argument as to what different knee designs there could be. Evolution will happen as it will and there is not much we humans can do to change it.
ReplyDeleteBut we could talk about it is how the knee came to be. There are two sides to this argument, both very obvious: creationism v. Darwinism. Creationism is pushing the irreducible mechanism “theory” which states that a mechanism is irreducible if it could not have evolved one characteristic at a time while always having a useful function. Even Darwin himself stated that if an irreducible mechanism was found, his theory would be non-existent in his book Origin of Species: “If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down”. Creationists believe that the knee is an irreducible mechanism. The knee has four main parts: two bones (femur and tibia) and two ligaments (posterior and anterior cruciate ligaments). The reason it is irreducible is because the knee cannot function without all 4 parts being present. Everyone has heard about a football player tearing/rupturing his ACL. When this happens, the player cannot not walk nor move his knee which exactly proves that Darwinism cannot exist because the knee is an irreducible mechanism.
(http://www.trueorigin.org/knee.asp)
Meanwhile, Darwinists counter this by insisting that there is a distinct flow chart of the evolution of the human knee:
Salamander -> Frog -> Alligator -> Opossum -> Cat -> Macaque -> Chimpanzee -> Human
Looking at pictures of the knees of these organisms (found at http://www.ejbjs.org/cgi/reprint/20/1/77.pdf), one can clearly draw connections from one organism to the next. These connections between organisms possibly prove once again that Darwinism is a distinct possibility.
(http://www.ejbjs.org/cgi/reprint/20/1/77.pdf)
Matt Micucci (coochqbk@sbcglobal.net)
As Matt said, evolution will happen as it may and there isn't really anything we can do to change it...consciously at least. However, we must also remember the principle of natural selection--the idea that over time, evolution will favor those traits that have been beneficial to the population. In simpler terms, the main pillars of this idea is that first, there is variation in the population in terms of traits, then there is inheritance of the traits as the population survives over time, next there is "differential survival and reproduction" (http://www.globalchange.umich.edu/globalchange1/current/lectures/selection/selection.html), which basically means that only particular traits that give the population an advantage will get passed on to the next generation. The theory of natural selection is a Darwinist theory, and thus I would have to disagree with Matt in that I don't think our body structure was created (creationist), but rather progressed over time as Darwin said, keeping traits that proved beneficial, and disregarding those that were not. Furthermore, I think this also shows that evolution is in no way random--though we may not know it, how we behave and utilize our body structure may have an effect on how it changes in the future because depending on how we use the characteristics, they may prove to be beneficial, or not.
ReplyDeleteI think that one way in which the knee might be improved in the future is that rather than having the three structures of "medial meniscus, the medial collateral ligament, [and] the anterior cruciate ligament" (Shubin 185), we might be able to have more than these three structures, which would be able to improve our range of motion, past what it is already. This relates to what Matt said about the pivot joint; having more ligaments would increase flexibility of the knee and possibly allow for a resistance to injury because there would be less of a possibility that the injured area would affect the function of the knee as a whole, unlike today, where a knee injury is a major hindrance to everyday movement and rigorous exercise.
There are many barriers that prevent us from being the "perfect mammal," as Sonia said, but in my opinion I think our main barrier is ourselves--we seem to have all the tools in our bodies to perform any function imaginable, but we take for granted what evolutionary history has created for us. As Shubin discusses in the book, we humans are becoming lazier and lazier...we've gone from hunter-gatherers to couch potatoes, and have begun ingesting substances that really don't belong in the body. This has made us prone to many diseases, the main one being heart disease. Heart attacks and strokes are caused by a blockage of the arteries as a result of accumulation and hardening of fats, called arteriosclerosis. Leukocytes take up lipids like cholesterol when the smooth lining of the arteries is damaged(Campbell & Reece 914), and this effect is increased when we allow ourselves to eat the unhealthy diets we do, high in LDL's and trans fats. Another effect of our lazier lifestyles is varicose veins. Our bodies are designed to be constantly active--when we move, blood is pumped more consistently through our body as the valves in our veins contract (Shubin 188). However, when we aren't active, the blood pools in our veins, causing the valves to malfunction and resulting in painful varicose veins that cause “swelling, fever, redness of the leg, [and] leg ulcers,” (http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002099/). Thus, I believe that we are only preventing ourselves from becoming a more "perfect mammal"--if we were to eat a healthier diet and to actually exercise like we were meant to, we would be able to fully utilize the carefully constructed bodies we have access to.
(continued...)
ReplyDeleteThe main way through which our body defends itself against disease is through the immune system. Our immune response is composed of two parts--innate immunity, and acquired immunity. Innate immunity is what we are "born with and [...] is nonspecific; all antigens are attacked pretty much equally" (http://uhaweb.hartford.edu/BUGL/immune.htm). An antigen is a substance that elicits an immune response, such as a virus. Two important examples of innate immunity are outside barriers, such as our skin, as well as our stomach. The acid pH in our stomach, combined with the protein-digesting enzymes present there, gives us the ability to "kill many pathogens" (http://uhaweb.hartford.edu/BUGL/immune.htm) present there. Acquired immunity is how our body adapts to repeated infections over time--it is the long-term version of our immune system. An example you might be able to relate to is chickenpox; after you've had the chickenpox once, the body's immune system will "produce specific antibodies against chickenpox" (http://medicalcenter.osu.edu/patientcare/healthcare_services/infectious_diseases/immunesystem/Pages/index.aspx) that will be released again if the same chickenpox disease is detected in the body. However, though we do have all these tools to fight disease, it's important to remember how we take them for granted--we have careless diets and lifestyle habits (like smoking), and in the future these mechanisms may not be enough to defend our bodies against ourselves.
Sources:
http://www.globalchange.umich.edu/globalchange1/current/lectures/selection/selection.html
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002099/
http://uhaweb.hartford.edu/BUGL/immune.htm
http://medicalcenter.osu.edu/patientcare/healthcare_services/infectious_diseases/immunesystem/Pages/index.aspx
Your Inner Fish
Campbell & Reece
Kathy Li, kathy2132@gmail.com