How do narrow and broad definitions of IQ heritability differ?

How do narrow and broad definitions of IQ heritability differ?

How has our improved understanding of genetics affected the nature debate about intelligence?

  

  Richard J. Hernstein and Charles Murray, the authors of The Bell Curve, belief that our genetic make-up predominates over environmental factors when it comes to our intelligence. According to them intelligence is uniform, quantifiable and measurable across different cultures and environments and regardless of history. Furthermore, they describe intelligence and even group intelligence as being largely hereditary and intractable. Apart from the scientific controversy that these statements provoked, the political implications emerging from such a narrow definition of IQ heritability are also extremely problematic.

If success and failure in a society is believed to be a matter of the genes that individuals inherit there is no sense in trying to ameliorate the situation of socially disadvantaged people. Not only social phenomenon’s like poverty and unemployment can then be interpreted as natural situations people with a lower IQ find themselves in but also measures for the improvement of social injustices would be ineffective, that is to say fruitless.

Fortunately, the improved understanding of genetics helps to develop a broader and less deterministic definition of IQ and IQ heritability. By less deterministic I mean that the IQ neither determines the fate of an individual nor is it stable over time or within a social group. While a broader definition of IQ heritability acknowledges the fact that genes influence the endowments which distinguishes individuals from each other it also takes into account that genes can change over time and that the gene pool within a group is even more diverse than between members of different groups.