There are any numbers of scientific theories that ought to bite the dust; that's what happens when you work at the frontiers of human ignorance. But most of them are at worst minor distractions or intellectual detours that barely escape the cloisters of academe. A scientific misconception that truly deserves a bullet in the back of its head would be one that has escaped into the real world to do real damage there. Perhaps the best current example is the notion of nature versus nurture.
It is a beguiling concept: highly intuitive and expressible through an alliterative, almost poetic moniker. Francis Galton, who was the founder of eugenics, a polymath and the cousin of Charles Darwin, coined the term. Unfortunately, like Galton's other monumentally bad idea, "nature versus nurture" creates a corrosive blend of conceptual falsehood and political potency.
The most elementary error that people make in interpreting the effects of genes versus those of the environment is to assume that you can truly separate one from the other. Donald Hebb, the brilliant Canadian neuropsychologist, when asked whether nature or nurture contribute more to human personality, reportedly said, "Which contributes more to the area of a rectangle, its length or its width?"
This was a clever reply, but unfortunately only reinforced the highly misleading idea that genetics and environment are orthogonal concepts, like Newtonian space and time. In fact they're more like Einsteinian spacetime: deeply intertwined and with complex interactions that can give rise to counterintuitive results.
Of course, the experts already know this. They realise, for example, that most children inherit from their parents not only genes but also their environment. Hence studies of separated monozygotic twins (who share most of their genes but not their environments). In addition, the idea of the extended phenotype—in which organisms, driven by their genes, act to modify their environments—has been well understood for over 30 years. And the science of epigenetics, though still very much in progress, has already demonstrated a wide variety of ways in which a gene's effects can be altered by factors other than its nucleotide sequence, and shown that these are determined in large part by the gene's environment (which, of course, consists in part of other genes, both in the same organism and beyond).
Unfortunately most of this is lost on the people, such as journalists and politicians, who seek to shape our society. Almost all of them seem to retain a naive 'Newtonian' view of nature and nurture, and this leads them into all sorts of intellectual fallacies.
A case in point is the brouhaha that accompanied the release in October 2013 of a lengthy screed on education policy written by Dominic Cummings, then advisor to the UK's centre-right education minister. Among other things, he pointed out (correctly) that academic performance is highly heritable. This led many commentators, especially on the left, to equate his statement with the belief that education doesn't matter. In their 'Newtonian' nature-versus-nurture universes, the heritability of a trait is an immutable law that can leave people—worse still, children—as prisoners of their genes.
This is nonsense. Inheritability is not the inverse of mutability, and to say that the heritability of a trait is high is not to say that the environment has no effect because heritability scores are themselves affected by the environment. Take the case of height. In the rich world, the heritability of height is something like 80 per cent. But this is only because our nutrition is universally quite good. In places where malnutrition or starvation are common, environmental factors predominate and the heritability of height is much lower.
Similarly, a high heritability of academic performance is not necessarily a sign that education matters little. On the contrary, it is at least in part a product of modern universal schooling. Indeed, if every child received an identical education then the heritability of academic performance would necessarily rise to 100 per cent (because any differences could only be explained by genes). Looked at in this way, a high heritability of academic performance is not a right-wing belief but rather a left-wing aim. But try explaining that to a newspaper columnist on a deadline or a politician with an axe to grind. Ironically, a central thrust of Cummings' paper was to argue that the British education system has produced an inept political elite and commentariat that is oblivious to such technical subtleties. In criticising his comments they have merely proved him right.
Thus the misguided concept of 'nature versus nurture' causes apparently intelligent people to confuse egalitarianism for fascism, to misunderstand the consequences of their own policies, and hence to arrive at unfounded beliefs regarding the education of our children. The only form of evolutionary manipulation that makes sense here is a concerted effort to eliminate this outdated and misleading idea from the meme pool.