A few days ago I went to the library in an effort to follow in my more philosophically-minded brother's footsteps and read The God Delusion. I am interested to see what he says, as I have heard him described, albeit hyperbolically, as the greatest thinker of our time. Unfortunately, the book was checked out, and so I settled instead for another book by Dawkins, entitled The Selfish Gene. I am probably about 3/4 of the way through it, and so far it is interesting and I have had almost no major disagreements with what he says. He focuses on evolution with respect to the genes of an individual (his catch phrase is the "survival machine", manufactured by the gene to facilitate its replication), and appears to be able to explain the theory pretty well as far as I can see. I do, however, have one big question about evolution which I have not found in his book thus far, which perhaps someone might be able to help me with. Natural selection is pretty much a universally accepted principle nowadays, and it seems perfectly sound to me - using Dawkins' language, genes which produce flawed bodies would fail to reproduce themselves and become less numerous in the gene pool, while genes producing fitter bodies would become more numerous. Eventually the unfit ones would die out completely and the species could be considered to have evolved.
The problem with this is the enormous complexity that we observe in the world. Evolution can explain species changing, but it does not seem to explain them growing more diverse. In fact, Dawkins himself points out that genes which fail to replicate themselves perfectly would become less numerous in the gene pool. Natural selection does not account for variation, it should actually eliminate it.
Suppose an animal's (say, a giraffe's) habitat is suddenly changed in such a way that only by having a long neck could it survive. We are inclined to say that the species develops and "evolves" a longer neck, but this is not how it happens. In reality, giraffes with short necks die off and giraffes with long necks live. This is the essence of natural selection. While we could say that the species "evolves" a longer neck, all that really happens is that the average neck length increased, because you killed off all the animals with short necks. The genetic makeup of a giraffe did not really evolve; that's like saying a school gets smarter when the stupid students drop out. No individual student will get smarter - it is only the average which increases. In the same way, a giraffe's neck could not get longer because giraffes with short necks died out. The giraffe could only have developed its long neck if there existed, prior to the need for a long neck, at least one individual of each sex within the population with the long neck that we see today. After the change, all the other giraffes would die and only these relatively few would be available to "rebuild" the species in their own image, namely, that long neck. But that neck would not, barring extremely fortuitous genetic mutation, be longer in the next generation than it was in the previous.
Natural selection can take advantage of an existing variation within a population to change the average genetic makeup of that population, but it cannot actually perform a feat of evolution as it is purported to have done. Proponents of evolution then seem to be left with random mutations to provide this variation which natural selection can then choose between. It is my understanding, however, before reading Dawkins' book, that mutations are incredibly rare and random occurrences which are overwhelmingly more likely to harm an animal than help it anyway, and in addition, Dawkins himself seems to say that gene mutation should decrease through evolution, as it is only genes which replicate themselves to the most reliable extent possible that persist through the ages.
Anyone care to explain this discrepancy to me? I may not have much respect for Dawkins, but too many other learned people are staunch supporters of evolution for me to dismiss it readily. I feel as though I must be missing something.
16 comments:
I happen to own The Selfish Gene. You were probably disappointed to find that it is not about whether God exists: it's pretty straight biology.
Evolution comes from two things: natural selection and random mutations. Mutations are actually very common, and when you think about how complicated most species are, that's not surprising. Most mutations are neutral, like my tiny pinky toes. They are passed along to offspring, and over time, helpful mutations become part of the gene pool while harmful mutations are "selected against". I suspect that over a large population without shoes, tiny pinky toes would probably be selected against because of the decreased ability to run from predators, but there's no way to know this.
"Selfish Gene" is not really a great title, because it seems to imply that the gene is looking ahead in time and planning to grow a longer neck, for example. In reality, it happens as you've described: animals with short necks die, leaving only animals with the long-neck gene to reproduce and pass their genes on. The gene has no ability to anticipate changes in the environment; it is simply passed along or not passed along.
Heh, no, I did know what it was about...I was amused though to note the somewhat ironic references to religion Dawkins made at scattered points - "What shall it profit a male if he shall gain the whole world, and lose his immortal genes?" comes to mind.
I was under the impression that mutations are very uncommon, and that something like your tiny pink toes are a result of the particular combination of existing alleles that you happen to possess. However if this is incorrect and mutations are actually everyday occurrences, then that would make the whole theory make a lot more sense.
"Everyday occurrences", relatively speaking. According to Wikipedia, there are 3 billion base pairs in the human genome, presumably virtually all of which would have to have mutated several times over at some point during the couple-billion-year history of replicator molecules (to put it simply; in actuality it would of course be far more complicated than a set of base pairs changing order randomly). Accounting for the number of creatures in existence and the length of a generation, we should be able to find a frequency threshold of the required mutations per replication. Without actually taking the time to do the math, I would guess that in order for everything we see to have arisen purely from mutations, that frequency would have to be relatively high.
All that would remain to verify is that the observed frequency of genetic mutation does in fact match (or exceed) this threshold. Which might be difficult, considering that genetics is a relatively new field of study in, well, genetic terms. But how long we would have to watch for mutations would depend on that frequency threshold we calculated. I'm sure someone has done it already...maybe I'll try to look it up later.
The problem is that we have never observed any new species being "evolved" even though, as you point out these mutations do have to be relatively high in frequency, so we don't really observe these changes at all. The existing biomass, where these changes are all taking place is far too large to monitor for developing species.
This is also, in part, the answer to your question on how frequently do these mutations occur? The mutations occur in individuals very rarely. However, when we talk about evolution we are using both a very large time frame and an entire species, so the probable occurrence of mutation goes up greatly.
Megan's example about the pinky toes may not be a true mutation at our stage in evolution. It may be a mutation that occurred to our great great grandmother and has been passed down from there. The sort muscle in my right eye is a perfect example of this. None of my siblings have this and neither do my parents, but I do have a uncle who does.
Natural Selection is easy to understand and observe, which is why it is accepted by nearly everyone. Evolution is very hard to understand and is potentially impossible to observe, which is why there is a great deal more controversy about it.
Evolution is not hard to understand and has been observed many times. There is NO CONTROVERSY except from people who think evolution means there is no god, and frankly I think those people would be better off burning Harry Potter books and trying to prove that the sun goes around the earth. Evolution has nothing to do with whether or not there is a god.
Research on mutation rates shows that they vary by species but are very common: about 175 per generation, of which an average of 3 are harmful and are quickly "selected against". Most are minor and easy to miss. Google "Nachman and Crowell" for more information way above my education level.
It is not true that there are no new species. You can find this out with a Google search. For example, bacteria have evolved the ability to digest nylon. People who claim there are no new species are generally hoping to see something like a cat giving birth to a unicorn. This would not be evolution, it would be creation. Good luck waiting for that to happen.
The ability to digest nylon is a evolved form only if the previous generation of bacteria were unable to do so. I would have to question your numbers though, 175 per generation of what? You have to have a specific control group to come up with numbers like that and it would be highly dependent on the number of creatures in the original generation. I will have to read your recommendations for more information on this. Evolution is not my area of expertise either but I agree absolutely; it has nothing to do with the existence of God on any level. But you just try and tell Dawkins that!
It is definitely an evolved form: Nylon is a man-made material and no bacteria could digest it until recently.
The fact that Nylon is man made does not prove anything. The capacity may have been in the original organism but was unusable (or used for something else) until Nylon was invented. I still have to read those articles you mentioned so this may actually be the case (I have no issue with there being a newly evolved form of bacteria) but they do have to be pretty strict about their measures.
175 per generation is definitely a lot more than I thought happened, thanks.
I've now finished this book and I must say, I thought it was pretty good. I am not nearly learned enough myself to verify any facts that he uses, but his approach seems quite sound.
The theory of Evolution got connected, very early, with the philosphical principle of materialism (better said, materialist monism: the belief that only matter is real). Unfortunately, the true debate - - which is philosophical - - gets confused with the biological theory. It's not just religious people who are confused about this; the worst culprits are probably prominent biologists, like Dawkins, who don't appear to be aware of the philosophical distinctions.
We live in - - perhaps - - the least philosphical culture in history.
hmmm....and yet the most dominant.
Nathan! What are you doing here? You should be over on Matthew's blog, answering his question (which, I must insist, you have neglected to do).
Then, please return and explain the significance of your statement. What does US dominance mean, in terms of our disinterest in philosophy? And do you expect US dominance to continue? (The Romans were not very philosphical either, and they dominated the world for a long long time!)
Well, it is a natural consequence...any culture primarily concerned will the material world would be predisposed to dominate the material world.
Ah, It was nothing but a jab, I know when I can't back something up...
Happy B day yo! (a little late I know)
What, are you suddenly too cool to blog?
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