Tuesday, April 6, 2010
Man's origin
Many people scrutinize the idea that humans evolved from ancestors of apes. On pages 193-194 Coyne speaks of several scientists who were timid to share their findings with the world and contradict the social norm. Explain the evidence that gave these men, like Charles Darwin, the confidence to provoke the world. Explain how closely humans are related to apes, physical traits, behavior, etc. Predict what factors may have caused the ancestors of man and ape to evolve into humans. What different factors would have caused that ancestor to evolve into the present day ape?
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the main difference between humans and apes is the way they get around. the ancestors of humans began their divergence with the advent of the foot. the foot, and consequently the bipedal gait, freed up the hands for use in manipulation, carrying, and eventually toolmaking. the new opportunities available to these bipedal apes stimulated an increase in brain size. as behaviors increased in complexity, the brain matter necessary to support these behaviors increased. individuals with a larger brain were able to better execute these behaviors and therefore were more likely to survive. another difference, which stems from increased brain size and more complicated social behavior, is a more complicated voicebox. humans have evolved much more versatile vocal cords to better enhance their social interactions through language. a third difference between apes and humans is humans lack of hair. this comes from the environment into which humans migrated. our ancestors went from a jungle, where fur was an asset because it kept off harmful parasites, to the savannah, where hair only served to overheat an individual. because of this, humans lost their hair, except on the top of their heads, where, due to their bipedality, the sun hit most intensely.
ReplyDelete"Our Kind" by Marvin Harris
http://samrhine.com/
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ReplyDeleteWe share approximately 98% of our DNA with chimpanzees (http://www.wired.com/wiredscience/2008/11/exploring-the-g/), for starters, which, in itself, is not enough to conclude anything unless it has already been established that evolution is true, in which case the high percentage of shared DNA indicates a relatively recent common ancestor between us and chimpanzees. There are also physical similarities: Apes are, as indicated by the percentage of shared DNA, more similar to humans than they are dissimilar. The differences are small: brain size, posture, hair growth, etcetera. Even horses share much of their DNA with humans (http://www.newjerseynewsroom.com/science-updates/researchers-complete-international-horse-genome-project-with-dna-map). Though our attention may often be brought to differences rather than similarities, observations like how the basic arrangement of bones in vertebrate skeletons are extremely similar--especially if we look more specifically at a single class such as mammals--are hard to pass off.
ReplyDeleteOne thing Intelligent Design proponents would argue is that something like brain size is not the only change indicated by this difference, because an increase in brain size is simply a side effect of having more complex neural circuits, which even in apes are terribly complex. People who believe man has been specially created above other animals would say that attributes like creativity have been given only to humans, and that is what makes them greater than other animals. Some of these people might think that "ideas" come directly from God. It would follow that, if humans are special, they might be the only creatures with free will; all others are simply biological robots. Therefore, it would be illogical and possibly offensive to think of humans and apes as being so similar that they could have a common ancestor, much less a recent one.
I disagree with the idea that creativity is unique to man, because I see creativity as simply the ability to relate to things that you have already experienced. As Mr. Roys would put it, "A chimpanzee cannot imagine a spherical chicken." However, I believe this is simply because we have developed a stronger ability than chimpanzees to call upon known concepts. You have to know what both a sphere and a chicken are in order to imagine a spherical chicken. A human baby also cannot imagine a spherical chicken. Of course, there are some chimpanzees that have been taught rudimentary "language," in which cases it would be possible to teach them that "chicken" is a sound that represents the idea of a chicken, which you would show them, and likewise "sphere" represents a sphere. It is probably true that this chimpanzee would not be able to imagine a spherical chicken, but first of all, I would argue that this is just because it is beyond the scope of their capabilities, and that these capabilities are the same as ours but on a lesser scale (brains are so complex that I don't know if there is a good way to prove this without very extensive research if at all); and second, how could we know if there were an instance in which a chimp did imagine the spherical chicken? How could it let us know? We could ask it, "Are you able to imagine a spherical chicken?" and then we would have no way to tell whether what it says is true.
Also, to some extent apes do have creativity. There have been numerous studies that involved apes using tools to solve complicated man-made puzzles without human interference or prompting. This extends to other animals, too, such as crows figuring out that they need to bend a small piece of metal into a hook in order to obtain a treat that is stuck in a narrow graduated cylinder. Some birds have also learned not only a large number of words but the syntax needed to create sentences they have never heard before (http://en.wikipedia.org/wiki/African_Grey_Parrot#Mimicry_and_intelligence).
This of course is all in addition to looking at the wonderful primate fossil record.