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I need to clarify something here.  Creationists do not just claim the above; they also claim that harmful mutations are more common than other kinds of mutations.  It is this that I am primarily objecting to, ...

Then take your objection up with the scientists who are saying it.  To be honest Jaimehlers you are tiring me - I actually don't have time to engage in a piss-ant debate with you, I have urgent and productive things to do right now.

I've explained my case and brought you evidence as I promised - so here are some quotes for you to digest:

From protozoans to mammals, evolution has created more and more complex structures and better-adapted organisms. This is all the more astonishing as most genetic mutations are deleterious.
The great majority of mutations are deleterious. "Due to selection individuals with more favourable genes reproduce more successfully and deleterious mutations disappear again," explains the population geneticist Richard Neher, leader of an independent Max Planck research group at the Max Planck Institute for Developmental Biology in Tübingen, Germany.

Mutation is the ultimate source of all the genetic variation on which selection may act; it is therefore essential to evolution. Mutations carry a large cost, though; almost all are deleterious, reducing the fitness of the organisms in which they occur

"Most mutations are harmful," said UNM Associate Professor Vaishali Katju, who is the grant's principal investigator. "They are the ultimate cause of most of our heritable diseases and yet, they also provide the genetic fodder for the origin of the wonderful diversity of life we observe all around us. Without mutations, there is no evolution.

Previous site-directed mutagenesis studies have shown that most random nucleotide substitutions are strongly deleterious in animal and plant ssRNA viruses. .... After performing similar experiments with phage Q?, we confirm that ssRNA viruses are extremely sensitive to mutation in general. Roughly speaking, the probability that a random single nucleotide substitution is lethal for an ssRNA virus is one third or higher, while viable mutations reduce fitness by 10–13% on average. .... Concerning the shape of the distribution, viable mutations of small effect are more abundant that those of large effect.

This work represents a study of the distribution of mutational effects on fitness for an RNA virus using explicit single-nucleotide substitutions. On average, mutations were deleterious even when lethals were ignored. 

Because deleterious mutations are much more common than beneficial ones, evolution under this relaxed selection will inevitably lead to a decline in the mean fitness of the population

Most Mutations in the Human Genome are Recent and Probably Harmful
Fast population growth has littered our genomes with five times as many rare gene variants as would be expected.
Using several techniques to gauge the effects of these mutations, which are the most common type of variant in the human genome, Akey estimated that more than 80 percent are probably harmful to us.

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