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3) Creatures adapt by natural and artificial selection of pre-existing genetic information. I believe that God endowed the original creatures with a large enough amount of genetic information to allow them to adapt and form new species (species being defined as reproductive isolation). | Quote | Ayala, Francisco J., “The Mechanisms of Evolution,” Scientific American, vol. 239 (September 1978), pp. 56-69.
p. 58
“A mutation can be considered an error in the replication of DNA prior to its translation into protein.”
p. 59
“The forces that give rise to gene mutations operate at random in the sense that genetic mutations occur without reference to their future adaptiveness in the environment.”
p. 63
“It therefore seems clear that, contrary to Darwin’s conception, most of the genetic variation in populations arises not from new mutations at each generation but from the reshuffling of previously accumulated mutations by recombination. Although mutation is the ultimate source of all genetic variation, it is a relatively rare event, providing a mere trickle of new alleles into the much larger reservoir of stored genetic variation. Indeed recombination alone is sufficient to enable a population to expose its hidden variation for many generations without the need for new genetic input by mutation.”
p. 64
“In any case there can be no doubt that the staggering amount of genetic variation in natural populations provides ample opportunities for evolution to occur. Hence it is not surprising that whenever a new environmental challenge materializes—a change of climate, the introduction of a new predator or competitor, man-made pollution—populations are usually able to adapt to it.
“A dramatic recent example of such adaptation is the evolution by insect species of resistance to pesticides. Insect resistance to a pesticide was first reported in 1947 for the housefly (Musca domestica) with respect to DDT. Since then resistance to pesticides has been reported in at least 225 species of insects and other arthropods. The genetic variants required for resistance to the most diverse kinds of pesticides were apparently present in every one of the populations exposed to these man-made compounds.” |
However, the only kind of adaptation that I am aware of are small changes: i.e. changes in length or size of the organism, changes in body color, resistance to pesticide, changes in amount of hair, etc. In short, changes in DEGREE of pre-existing structures and functions. I am not aware of any organism that has "evolved" if this is to mean something like, for example, a legless worm growing legs, a whale whose flippers turn into legs, etc. |
I don't think scientists would disagree with any of the qutoes from this section, although they would draw different conclusions from them than you do. It appears to be an common misconception that people have that mutations occur in response to selective pressure, that when climate change, or introduction of a new predator, or introduction to a new resource occurs some lucky mutant will just so happen to get the right mutation at the right time. This is of course not how it works. Instead mutations are always occuring. They provide the raw materials for much evolution occurs. So the small set of descendants with a rare mutation are already in the population with the change occurs that takes a neutral mutation and turns it into a positive mutation. From there allele frequencies are changed over time (one of the common definitions of evolution), which causes this mutant to become a dominant gene.
You may think the odds of this happening are vanishingly low but let's look at a real world situations. The average human has around 100 point mutations per individual per generation. Their are roughly 6 billion humans, and the human genome is around 3 billion base pairs in size. So in the current human populace we have 600 billion mutations to the 3 billion base pairs. This leads us to believe that in all likelyhood every single base pair in the human genome is mutated in at least 1 human somewhere. This is on top of all the genetic variation existing in our ancestors, and all the small enclaves of previously mutated genes that exist. So even if 99.99% of all mutations are selectively neutral, and 99.99% of all non-neutral mutations are negative, we still have 6,000 positive mutations in the human genome right now. Not to mention the huge amount of neutral mutations that if a change to the environment were to occur could become positive.
Also, you are mostly correct in you assessment concerning "small" changed (most scientists wouldn't consider these small changes, they would consider them macroevolution). Evolution can only use the raw materials provided to it. This is why when you look at animals their "design" is haphazard. No engineer would build a machine this way. The closest thing that comes to mind for me is a Rube Goldberg device. Sure the little ball makes it all the way to the cup, but it takes the most improbable of paths to do so. Carnivores have 4 limbs and a tail, Aves have 4 limbs and a tail (though their forelimbs have become modified into wings, and their tail has become more useful for flight), Primates have 4 limbs an a tail (even the "tail-less" apes have the remnants of a tail that doesn't break the surface of the skin). Evolution uses existing parts and modified them to take advantage of new ecological niches. If you look at the Primates (feel free to exclude humans, i'm still fuzzy on how you would categorize those in your system), how different is a south american monkey, from an african great ape? Are Primates all of the same Kind? are the size change, and color differential of all modern primates just examples of microevolution under your system?
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4) Random mutation, as far as I can tell, does not create new features or functions such as eyes where ther were no eyes, legs where there were no legs, etc. Random mutation has been well known for a long time, however, to be mostly HARMFUL to organisms. | Quote | Wills, Christopher, “Genetic Load,” Scientific American, vol. 222 (March 1970), pp. 98-107.
“Some mutations are ‘beneficial,’ that is, the individual in whom they are expressed is better able to adapt to a given set of environmental circumstances. The large majority of mutations, however, are harmful or even lethal to the individual in whom they are expressed. Such mutations can be regarded as introducing a ‘load,’ or genetic burden, into the pool. The term ‘genetic load’ was first used by the late H. J. Muller, who recognized that the rate of mutations is increased by numerous agents man has introduced into his environment, notably ionizing radiation and mutagenic chemicals.” |
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Dave, there's a reason using 36 year old science data is dangerous. In 1970 when this article was published the Neutral Theory was brand new. Neutral Theory in a nutshell simply states that their are a large number of neutral mutations. After we had a better understanding of molecular evolution this became fairly self evident.
Codon's code for amino acids, but there is more than 1 codon that codes for each amino acid. For example UCU, UCC, UCA, and UCG all code for the amino acid Serine. CU* codes for Leucine, GU* codes for Valine, GC* codes for Alanine, etc. You'll notice a pattern here. The third nucleotide in a codon is often irrelevant. This means that any point mutations to that nucleotide will be silent (will have no phenotypic change to the organism). Furthermore many amino acides in a protein are interchangable (for example sometimes any hydrophobic amino acid will do). Other amino acids do not alter the way a protein is folded, and have no effect on the finished protein. After that, there are a large amount changes that could occur that are not positively or negatively selected via natural selection, they are simply different. That is what happens if the mutation lands in a coding region, but there are huge swaths of non-coding dna in our genome. There is junk in the form of long repeating sequence, there are pseudo-genes, and there are retrovirus remnants. If a mutation occurs in these areas it won't effect the organism at all. Adding all these together the Neutral Theory posits that the vast majority of mutations are selectively neutral.
The Wills quote above would still be correct if you added the words "easily visible" before mutations. Of the changes that are detectable at all negative changes are much more likely to be detected. Negative changes tend to be dramatic, often fatal. Those types of changes are immediately identified. Since the person's life may be in danger they are studied intently. On the other hand a positive mutation may occur in a human without anyone ever noticing. For example, there is a mutation in humans that causes tetrachormatic vision. Instead of having cones that detect 3 different wavelengths of light, they have 4, given them better color differentiation than other humans. A person could go through their whole life without realizing they have this mildly benefitical mutation.
[Note: I am a layment. Any person who actually studies this for a living feel free to correct anything I said above] |
