I haven't read the book by Murray and Hernstein. However, I read a ponderous, endless symposium on it in two issues of the Skeptic journal, v3 #3 and 4, 1995. I came to the conclusion that the debate has not changed since I read about it in the '70s. It may not have since the 1840s. So I can give my remembrances and be completely up to date.
At first, I thought all the namecalling was wrong. The anti-Bell Curve people call the pro, Nazis. The pro-Bell Curve people call the anti, Commies. Now I'm not so certain this isn't the real essence; and the statistics, studies and logic (such as it is), the lacunae of science, aren't a coverup. This is a matter of people's egos, and maybe a few ids. Of petty animosities, prejudices and conceits.
The anti-Bell Curve people attack the pro's position with the kitchen sink. They point out its logical fallacies, its factual errors, its political agenda. This hides the fact the anti-Bell Curve people have no position of their own. They cannot, it would be politically incorrect; this subject is taboo. All they can do is dance around it and hope no one notices.
The problem is that, scientifically speaking, if the antis take no position, the pros win by default. This is true no matter how sloppy the pros are. And the pros are slop city.
The pro-Bell Curve people are more interesting: they take a position. How you defend a position depends upon your purpose. The purpose here is to prove Whites are superior and Blacks inferior. All other facts are ignored or minimized.
For one thing, they never get into what IQ actually is. They describe it in glowing generalities and leave it at that. They would just as soon have it worshipped as a God. If not a golden calf, a paper calf. Certainly, its virtues are proven more by faith than reason.
As far as I can tell, the IQ is supposed to predict the amount of formal education you will receive. To some extent, good formal education: Harvard rather than East Podunk. To do this, it tests the skills needed. Put in these terms, people will say that IQ doesn't mean anything. An average person often shows far more common sense than those eggheads. Even the eggheads will equivocate.
Also, the pro-Bell Curve people try to minimize environmental influences, like education and income. They love to average differences out. They are more people of the 50th percentile or the 25th than of the 10th percentile or the 5th. They certainly would never compare a first grade education with a high school or college education. Or the IQ of a family living in a hovel on potatoes and one living in a mansion on caviar.
When push comes to shove, the pro will admit that if you tutor kids or even train them in the skills needed, their IQ will increase dramatically. They admit Head Start enrichment increased IQs. They admit one Wisconsin study increased the IQs of minority children from 85 to 110.
They usually argue that the IQs do not stay changed. If the regimen is not kept up, IQs will drop. They are very right, but isn't that the idea behind education? That you have to give people a certain number of years of education, at least when you're young. A person who only has a First Grade education would not be considered educated. Nor would one with only an Eighth Grade education.
And supposing a person with a high IQ in adulthood went from Corporate Vice President to hod carrier and there was not much need for reading and writing, would his IQ remain high? Supposing a physician loses his license and becomes a delicatessen owner; would he still be considered medically knowledgeable after a while? On this, the pro people are mute.
There is another objection to tutoring kids. It is very expensive. One writer, Eyesenck, the psychologist and professional iconoclast, said that it cost a $100,000 per pupil. Of course, tutoring is what millions of Middle Class parents do with their kids. I know schools in my Gold Coast/Blue Ribbon county demand it of parents.
Then there is the matter of different racial/ethic groups. Most pro-Bell Curve people would like to ignore these facts. Poles in America tested low IQs during World War I but normal IQs during World War II. Catholics have low IQs in Northern Ireland but not in America, and the Japanese Burakumin have a low IQ in Japan but not Hawaii. The facts are the same for Blacks, only in reverse. There is no proof Blacks in Africa have lower IQs than Whites.
The writer Eyesenck, alone among hereditarians, has tried to explain the last fact. He suggested intelligent Blacks were systematically killed off in the Old South. I know of no documentation for that. In fact, Blacks who could become blacksmiths or carpenters were worth more to their masters. Of course, I suppose slaves rarely were allowed to read Cicero or Shakespeare.
I have a simpler explanation: groups not college, or academically, bound do not acquire academic skills. When you will be forced to spend your life as a tanner or a sharecropper, there is little reason to bone up on your differential calculus. There is not very much even if the only problem is years of being called white, oreo or zebra. And we know the problem is more than that.
One last point. Some of the people in the Skeptic seminar claimed that there was a correlation between races with large brain size and high IQ. And this showed heredity was the cause. One even suggested that there was an inverse correlation between penis size and IQ. We get into less than quaint Victorian notions about reason, emotion and race. Probably the best explanation is the liberal one, coincidence: as far as I can tell, only three races were ever examined.
There may be another explanation: recent findings have shown that the brain size expands with use. This only works with the brain; an expert assures me, despite folklore, penis size does not expand with use.
In sum, nobody has actually tried to approach the IQ scientifically; both sides have been faking it. So, I will accuse anyone who is pro-Bell Curve of being a Nazi. And they are entitled to call me a Commie. Also, I invite them for a drink to discuss the matter. (Given the state of my health, I'll stick to Diet Sprite.)