I’ve been telling you, Charles Murray is an ignorant hack. I can’t stand listening to this know-nothing pontificating on genetics when he’s so full of shit on the topic, which doesn’t stop him from being arrogantly confident about it.

Anyway, here’s a good critique of The Bell Curve — it’s hard to believe we still have to argue about it.

Understandably, these arguments provoked the ire of progressively minded scientists and commentators. However, the sweeping and reflexive manner in which opponents of the hereditarian arguments advanced their objections to The Bell Curve often led these critics to adopt counterproductive conclusions. Unhelpfully, they conflated two distinct issues. The first is the question of what it means to claim that something is genetic, and the second is the inevitability of certain life outcomes based on the biology of a particular organism.

Properly speaking, genetics concerns some characteristic of an organism varying across individuals in a group in a given context. It is, by definition, not an explanation of the behavior or development of a given individual in a given instance. Conflating the issue of the causes of differences with that of the inevitability of the development of a particular organism is an important part of the hereditarian rhetorical strategy deployed by the likes of Herrnstein and Murray. To the extent that their arguments have managed to gain some traction in the world, it has been because they have managed to convince their critics to commit the error for them.

Whoa there — the heart of my criticisms of Murray has always been that genetics is not as determinative as the naive people who learned about Punnett squares in fourth grade think. But do go on, this is an important definitional issue and bears repeating.

But the confusion in Murray and Herrnstein’s thinking doesn’t just stop at their pessimism about the kind of practical responses to differences purportedly caused by genetics — it goes all the way down to their understanding of what genetics is. Let’s start by clarifying what we mean by “genetic” and outline why that which is genetic is not necessarily inevitable. For one, genetics deals with groups of organisms rather than the life outcomes of individual organisms. All organisms have genes, but it takes groups of organisms to have genetics because genetics is ultimately about how variation is structured within a group.

Take a single tomato plant in isolation. It has a genome that is between one-fourth and one-third the size of that of a human’s in terms of the raw amount of DNA. Inside its genome are a few tens of thousands of genes, which, in this case, are stretches of the genome that form a chemical template for the cellular production of the proteins and other biochemicals that are vital for the structure and function of organisms. However, since we are dealing with a single plant at a single point in time, there is no comparative context that would allow us to identify the differences among organisms that characterize the rich diversity of life.

Exactly! This is also why it’s important that students actually do real crosses with real organisms. The abstractions of theory might tell you that oh, one quarter of the progeny will have a particular phenotype, but when you sit down and have to closely examine a thousand flies, you get to see all the variation you did not predict and you learn that it’s never as simple as the models tell you it is. The variation is also interesting.

But yes, genetics is fundamentally probabilistic. You can’t use it to predict individual destiny. It’s also the case that genetics has significant interplay with the environment.

But even having many organisms to compare is not sufficient for a biological system to display genetics in the proper sense of the term. Genetics in the sense that matters is ultimately about variation that arises from genetic differences. To see this, think again about tomatoes. They can be cloned with ease by taking cuttings from a single plant and growing them in their own allotments of soil. Genetically, the different newly individualized plants will be identical to one another, with the exception of a very few mutations — spontaneous changes to DNA that can occur during cellular replication.

If we were to compare a large number of these cloned tomato plants, we would find many differences among them. The shape and sizes of leaves would differ, as would the coloration of the fruits and the pattern of branching along the stalks. Since, on account of being clones, the plants are all genetically identical, these differences could not be attributable to genetics. While each of the plants has genes and we have a group of plants to form the basis for comparison needed to establish that there is variation, there are no genetic differences among the plants that could account for any of that variation. That is, while our tomato plants have genes, they display no genetic differences among one another despite having physiological differences.

Yes, that’s always been obvious if you actually look at populations. I had tanks of zebrafish that were about as genetically uniform as you can get, highly inbred for over a century — yet I could recognize individuals in a tank and see differences in behavior. I’ve only been inbreeding spiders for a half dozen generations, but I don’t see variation diminishing, at least not yet.

How do people take Murray seriously when his fundamental understanding of biology is so wrong?