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Re: Ch. 2 - Evolution
The only point I thought really worth mentioning in this chapter was the definition Scott provided for a species. I have no doubt that she's representing the common, contemporary scientific definition of species; still it raises all sorts of question. I'll quote:
"A species is composed of all the individuals that can exchange genes with one another." (p. 41)
Later in the same section, Scott mentions mules. But what species would a mule (or a liger) belong to? By definition, they can't be their own species: they're sterile, so they can't exchange genes with anything. So how do you determine whether they belong to the species of horse or the species of donkey? Or do they have no species at all? Is hybrid distinct from species? Am I just being naive here?
Actually, I'm a little curious as to why science retains a concept of species at all. As early as Darwin it looked as though evolutionary theory threatened to dissolve the category of species, but at some point unknown to me someone apparantly found a reason and a way (definitional, it would seem) to retain the categorization. It makes me wonder how artifical our notion of species might be.
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Re: Ch. 2 - Evolution
Quite a good overview of evolution, in my opinion, considering the rather short length of the chapter. Here are some points of interest I found:
1. The definition of "life". Life is generally characterised as the ability to reproduce and use energy. Of course, then we are left with all kinds of problems concerning things which we do not normally think of as alive but which nonetheless seem to have these qualities.
For instance, is fire alive? It certainly replicates itself (ever seen a fire spread?), and it also seems to acquire and use energy, grow, and even move. Could we consider fire a living thing? I think that perhaps fire can give us an idea of what "life" could be like for non carbon-based or non DNA-based lifeforms that may exist elsewhere in the universe.
Then there is Scott's own example of a virus. It seems to be non-life until it becomes parasitic upon something already alive. Is it non-life up until it attaches to a living cell and replicates, or is it somehow in-between, or what?
As with Mad's discussion of the concept of "species", I think the boundary between life and non-life is arguably quite arbitrary. Because life almost certainly arose from non-life, we have the same sort of gradation that we see in speciation. With species it becomes nearly impossible to determine when speciation occurs--you can only tell at the extreme boundaries of a lineage. For example, the genetic differences between a parent and its offspring are minimal--but the differences between a parent and its great-great-great-great-great-great-great-great offspring are much--I don't mean to be redundant--greater. Scott discusses how clay may have had a part in the creation of life, and this can be seen as non-living semi-life, then we get viruses and simple protein chains, and then we get DNA-based organisms--and it seems incredibly difficult and arbitrary to just decide that at one of these points life occurs whereas everything before it is not alive.
In the end, such distinctions are purely for conceptual value, and aren't really important. It doesn't matter how we define species or life, so long as we recognize that the reality shows a gradation of different characteristics. It seems similar to the problem Wittgenstein noted when trying to determine the essential characteristic of the word "game"--it seems there isn't one, but there appear to be "family resemblances", meaning there are a cluster of basic characteristics and any thing that has a particular number of these may be described as a "game".
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Re: Ch. 2 - Evolution
I think that perhaps the most interesting part of this chapter was Scott's distinction between marks of "tinkering" and marks of "design". And even though she does not make this point herself, I think that this distinction is actually very helpful in making a strong probabilistic case against God's existence.
Now, when we observe biological lifeforms, we typically see that their anatomical structures are often inefficient and could feasibly be remedied. A common example given is the human blind spot. Evolution explains why we have such a blind spot--because our eye evolved gradually from parts which once had nothing to do with sight, and as a result some of the parts where not optimal for the best design, but evolution produced the best sight-giver out of these spare parts...and it happened to leave a blind-spot that it couldn't "evolve away". Evolution, unlike design, predicts such inadequate and opportunistic tinkering.
Here's where we can start arguing against God's existence. Let's say the Abrahamic theologians are right, and God is best defined as an omnipotent, morally perfect creator of the universe who has a special interest in humanity. The problem, then, is that humans seem to be "tinkered" rather than designed. Why would an omnipotent creator interested in the well-being of humanity give them a bone structure that wasn't optimal for bi-pedal motion? Why would he give women birth canals that are more optimal for four-legged creatures than bipeds? Why would we have an appendix and other seemingly useless parts, like junk DNA? Why would our bodies be like ecosystems, dependent on various forms of bacteria for our very survival? It seems to me that a designer would not incorporate such flaws in his favorite designs. Why wouldn't he make us better bipedal creatures, without hernias and birth problems? Why wouldn't he rid us of tonsils, wisdom teeth, and the appendix, which can be very dangerous to us and which often need to be removed? Why wouldn't he make our bodies self-subsistent, or give us high-powered chloroplasts so we could be like hybrid cars--eating energy as well as producing it from the sun? Even a child can think of numerous improvements that can be made to the human form, so why couldn't an omnipotent designer with our interests in mind think of it?
This doesn't constitute a full-out disproof of this type of God, to be sure. An omnipotent God can do anything it pleases, including create bad designs. And a morally perfect God, while you wouldn't think it would give us useless teeth that often get infected and even kill people if not properly treated, could easily be reconciled with the seeming "evils" of our suffering bodies by citing some unknown reason that makes all these evils worth it, or arguing that these bads give us "character" or help us appreciate good better.
However, it doesn't seem very probable that a morally perfect and omnipotent being that cared about us would give us such inadequate bodies, and the fact that evolution seems to explain these facts much better (it specifically predicts such signs of "tinkering"), we seem to have reason to disbelieve in such a God.
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Re: Ch. 2 - Evolution
Saint Gasoline: In the end, such distinctions are purely for conceptual value, and aren't really important.
They may not be all that important for biology, but they have ramifications in other areas. For example, speciation may have some importance in moral concern -- if there's no hard and fast line between species, then our notions of murder and cannibalism become somewhat nebulous and fuzzy. I think that's one of the problems that contributes to the controversy between evolution and creationism -- conceptions that don't have much solid import in one can seem to have radical implications in the other. Creationists, I think, feel a vested interest in defending ideas that don't have much importance in a strictly biological view of the world. And the fact is, very few of us have a strictly biological view of life.
Saint Gasoline: Why would an omnipotent creator interested in the well-being of humanity give them a bone structure that wasn't optimal for bi-pedal motion?
Again, these are problems that existed before anyone gave any serious consideration to evolution, and I don't see that neo-Darwinian thought really adds anything to these problems but the varnish of some additional details. Is less than optimal bone structure really as damaging to the idea of an omnipotent, benevolent creator-God as the existence of suffering? So why should the notion of "tinkered evolution" be any more troubling to theists than the problem of pain, a problem that has been noted and expressed at least as early as the Book of Job?
...and the fact that evolution seems to explain these facts much better (it specifically predicts such signs of "tinkering"), we seem to have reason to disbelieve in such a God.
I don't think the explanatory power of evolution has anything to do with the question of whether or not there is a God. That's one of the problems of this whole controversy, as far as I'm concerned -- people seem to have a vested interest in making evolution some sort of answer to theology, when it really need have nothing to do with it.
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Re: Ch. 2 - Evolution
My final point of interest is in regards to speciation. I think the problem that creationists have with claims of speciation in evolution involves their misunderstanding of what a species is. Given Scott's examples of speciation--fruit flies that become reproductively isolated over many generations, island species that show characteristics of the nearest mainland counterparts but which can't reproduce with them--a creationist could simply respond that these aren't evidence of "speciation". They would say, "Show me a turtle giving birth to a duck." Of course, evolution would never predict such an absurd thing to occur. Evolutionary change is very slow and we wouldn't expect such a huge leap in design space to occur in one generation, as is the case with a turtle birthing a duck. However, the basic point is that the evidence for speciation is tied up with a definition of species as reproductively isolated. A creationist sees the definition of species differently. Two hummingbirds that cannot reproduce with each other are nonetheless two of the same "species" or "kinds". For a creationist, "species" is a labelling concerned with physiological differences, not reproductive abilities.
In essence, this explains why creationists are often not convinced when given evolutionary explanations. It all boils down to the fact that they do not see testable theories as better than non-testable inferences or conjectures. Their sole criterion seems to be logical coherence. Because "design" coheres with all the evidence, it is a good idea, according to the creationist. (Nevermind that it would cohere with any evidence whatsoever, even if things suddenly changed into their opposites overnight.) A creationist doesn't care about testability, so they have no reason to see evolution as a superior theory. Evolution specifically predicts homologous parts, vestigial organs, a progression from simplicity to complexity, and a characteristic distribution of species? So what, they say. Design can account for this, too.
Speciation isn't evidence of evolution because a "species" is defined by a creationist to be more than the production of reproductively isolated groups. Transitional fossils aren't evidence, either, because they just show that there are THREE "kinds" or "species" (reptiles, reptile-mammals, mammals) rather than the gradual progression of reptiles into mammals. Essentially, creationists have figured out that science is a game of "truth without certainty" and they exploit the uncertainty, showing that because nonfalsifiable ideas like design can also explain the evidence, scientific theories are always questionable. Their mistake, however, is that they think their ideas are plausible merely because they show that scientific theories are underdetermined.
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