Nope, it is not an issue of something being good or bad by some universal forces. You see our DNA is very finely tuned "machine" where genes cooperate with each other. In this case any changes in this machine will be mostly negative. Imagine an old fashion watch. Open it and look at all the gears nicely working inside. Now try to do a random modification to any of these gears. Add more teeth to some gears, make square gears, o much bigger, and I assure you that the watch will stop working. Only in rare situation little modification of fine tuned watch will be positive. Like a modification making all gears physically stronger, or all proportionally bigger. Of course, if environment rewards such change.
It is a similar situation with our DNA. Most changes are distractive, varying from very destructive to mildly negative to neutral, and only microscopic amount of changes are truly positive.
Very nice job of explaining the science in simple language for those of our posters who haven't kept up with the scientific literature.
Those who have already know that the science seems to show that de novo mutations in the vast majority of cases are not beneficial.
I don't know how it can get much clearer than this statement in the above cited source:
"De novo mutations tend to be more deleterious than inherited variation because they haven’t undergone the same level of evolutionary selection.
Just as a general proposition: "Beneficial mutations are rare."
http://rstb.royalsocietypublishing.org/content/365/1544/1153
"
One of the earliest theoretical studies of the distribution of fitness effects was done by Motoo Kimura, an influential theoretical population geneticist. His neutral theory of molecular evolution proposes that most novel mutations will be highly deleterious, with a small fraction being neutral.[61][62] Hiroshi Akashi more recently proposed a bimodalmodel for the DFE, with modes centered around highly deleterious and neutral mutations.[63] Both theories agree that the vast majority of novel mutations are neutral or deleterious and that advantageous mutations are rare, which has been supported by experimental results. One example is a study done on the DFE of random mutations in vesicular stomatitis virus.[50] Out of all mutations, 39.6% were lethal, 31.2% were non-lethal deleterious, and 27.1% were neutral. Another example comes from a high throughput mutagenesis experiment with yeast.[55] In this experiment it was shown that the overall DFE is bimodal, with a cluster of neutral mutations, and a broad distribution of deleterious mutations."
https://en.wikipedia.org/wiki/Mutation#Distribution_of_fitness_effects
Now, I'm done. This is like arguing the shape of the earth with flat earthers, or evolution with Creationists.
As to IQ, the intelligence quotient is a very particular term and measuring it can only be done by means of the kind of hours long testing done one on one by educational psychologists which measure memory, speed of processing, visual-spatial ability, pattern recognition and on and on. Pen and ink mass produced tests, and even worse, tests like the SAT do indeed measure what is learned, not what one is capable of learning quickly.
That innate IQ is highly heritable, and relatively stable if the testing is of the kind I described.
Ed. You're absolutely right about the very high number of spontaneous abortions, and I'm not just talking about what are popularly called "miscarriages". Those are the situations where a woman knows she's two or three or four months pregnant and the fetus aborts or dies in utero and has to be removed, which is even more of a horror.
The fact is that often, when a woman is "late" or "skips" a period, she is often pregnant, but the fetus aborts because of mutational abnormalities.
Also, some people seem to be unaware of the number of children today born with less serious mutational abnormalities, or what are sometimes called birth defects. Parents just get their child the proper medical care. In prior eras, these children were still born or died shortly after birth.
