I recently passed my final class for a Master's Degree in Education Policy, doing a project in the gap between scientific knowledge of cognition and how that knowledge is socially applied. As such, I touched on the Bell Curve a bit, and have a few comments to make on it.
First off, I would like to discuss a way that a certain group of people - people of African descent, are genetically and biologically inferior to another group of people, those not of African descent. A pretty strong statement, but what I have to say in this regard is scientifically and socially non-controversial. Some people of African descent have a change in single base pair that codes for a single amino acid in a gene that codes for a certain protein, namely hemoglobin, the protein that carries oxygen in the blood. Because a single amino acid is changed, the molecule, under certain conditions, will be pushed against other hemoglobin molecules because it is now hydrophobic. The result is the condition known as sickle cell anemia, which can be very dangerous or fatal. This disease only effects mostly those of obvious African phenotype, or, as we say on the streets, blacks.
If someone states that black people can be genetically inferior to white people in their ability to transport oxygen, why is suggesting that one race or group of people is genetically inferior to another in intellectual ability so much more controversial, scientifically and socially? Is it because people would take a genetic condition affecting their body as an external disability, but to suggest that they are stupid is a more personal matter? I think part of it is that, but my own annoyance and objection to theories such as these is that they have no clear science behind them.
I have read much of the controversy surrounding the Bell Curve, and much of it seems to focus on the fact that the author's were a bit too reductionistic in their science, that they did not totally take seriously how institutionalized racism and classism can affect people's lives, as well as the fact that cognitive abilities do not exist in a social vacuum. But my objections come from a different direction: that the authors were not reductionistic enough. What the authors do is connect a social phenomena (intelligence and its connection to what could be considered social success) to a biological explanation (genetics), without explaining what that actually means. They use genetics the way Stan Lee does: we can accept, in the pages of the X-Men, that a "mutant gene" can make someone shoot beams of light out of their eyes. But if someone is writing a book where they suggest that millions of people will never be able to enjoy all society has to offer because they are simply born stupid, they should come up with a better explanation.
So my problem with the Bell Curve is that it does not explain what the biological difference is between intelligent and non-intelligent people. If there is a genetic difference, it can be identified and tested for. We should be able to know exactly which proteins are different between the cognitive elite and the normal folks, we will know just which one of the thousands of proteins in the brain has a selenocysteine in place of a normal cysteine that lets us get into med school, and we will know which enzyme accidentally shunts tyrosine from its normal adrenalin metabolism into producing octopamine, which is what makes people go on benders and end up in prison. But in the hundreds of pages of The Bell Curve, not a single actual biological mechanism is proposed for intelligence. The authors, neither of whom are biologists, use "genetics" the way most lay people do: as a Canadian Girlfriend that can be mentioned as needed, without needing to mention any particulars.
If the authors wish to hypothesize that cognitive attitudes and abilities seem to be rather unchangeable by social intervention, that is a fine social science hypothesis. When they move into the realm of biology, however, they have an obligation to actually present some biological facts or reasoning, rather than using biology as a way to avoid the fact that they have no actual sociological evidence for their hypothesis.