Political policies are not ideas existing in a vacuum. They are based on descriptive beliefs or assumptions about the nature or natures of humanity and the explanations for differences among human beings and population groups. They are also based on fundamental prescriptive beliefs about how humanity ought to be governed.

There used to be a nature-nurture debate or, if you prefer a heredity-environment debate about the extent to which observed differences between individuals and between population groups – races if you like – were attributable to heredity or environment, culture or upbringing.

There is now a nurture-nurture consensus based on an assumption – a false assumption – that all observed differences between individuals are attributable to upbringing and experience and that differences between population groups are attributable to culture or environment.

If these assumptions were based on soundly-conducted empirical research, all would be well. However, when such research was permitted, all the evidence suggested most of the observed differences were attributable to hereditary differences rather than to differences in environment, culture or upbringing.

Now the opposite nurturist assumption is made and attempts to question that assumption by scientific research are forbidden. Any academics found to be questioning that false assumption are demonised and persecuted professionally and personally, with dismissal being the ultimate weapon.

Now all academic institutions, the media, business and commerce, as well as political parties and pressure groups adhere to the same nurturist falsehood. How did this absurd situation arise?

It seems that responsibility lies with two identifiable individuals, in particular: Franz Boas (1858-1942) and his acolyte Margaret Mead ((1901- 1978 ). They styled themselves as social or cultural anthropologists , to distinguish themselves from true anthropologists who recognised the role of heredity in distinguishing different branches of humanity.

Margaret Mead noticed the enormous differences in behaviour between different population groups and drew the conclusion that the differences must be cultural. This was based on the unexamined assumption that hereditary differences could be discounted.

Why is all of this relevant to public policy?

Well the main area is in the areas of immigration and emigration but particularly immigration. Since the Second World War, several European countries have persuaded themselves that they were suffering from labour shortages. These alleged labour shortages were met with large numbers of immigrants from the Caribbean and the Indian sub-continent.

Later from the late 1960s improved birth control methods have resulted in birthrates that have fallen to below replacement rates, resulting in falling populations or ageing populations. They have sought a remedy to this by importing large numbers of people from the Third World.

If these replacement populations had indeed been identical substitutes for the unborn indigenous populations, all might have been well. However, levels of intellectual ability and behaviour are not superficial and cultural but deep-rooted and inborn. If you bring in populations from the Third World you do not turn the immigrants into substitute Britons or other Europeans. You turn parts of our country and other European countries, into the Third World.

However, there are other areas of public policy in which the predominant influence of heredity over environment is relevant.

Education is an obvious one. If all children had equal potential, it would be quite reasonable to subject all children to an identical form of education and you might expect to witness similar levels of success.

However, all children do not have similar potential levels of ability, so we have witnessed widespread failure and unnecessary debt but booming educational institutions and vice chancellors living lives of luxury and reward.

In the area of law and justice, we might expect all people to be born with an equal potential for leading law-abiding or criminal lives. If we believe that falsehood, we might conclude that all we need do is to remove the influences that produce criminality and we succeed in eradicating crime.

However, reality does not work like that. You can take the offender out of the allegedly harmful influences but you cannot take criminality out of the repeat offender.

Clever people look for causes of the epidemic of gun and knife crime and they develop hypotheses that are as ingenious as they are implausible. However, demographic change is the one hypothesis that is avoided. If theorists find themselves drawn to that conclusion they exercise the device that Orwell called crime-stop and move their thinking into a more acceptable and a safer direction.

When a particularly brutal or senseless crime has been committed theorists agonise and ask, “What could have turned the perpetrator into a heartless killer?” If they fear that the interviewer might make a heretical suggestion, our theorists will answer a question that has not been asked. “People are not born killers,” they say. However, our theorists have nothing to fear. Interviewers have been trained far too well to ask heretical and intelligent questions.