Science likes to present itself as empirical fact when in reality it is interpretation of those facts. As a result, many claims are made which do not resemble reality but serve a political agenda. This especially becomes popular in any topic concerning the equality of people.
As a subset of those topics, any science on the lack of a link between intelligence and genetics is suspect because the lack of that link is central to the Leftist idea that we are all equal. If intelligence is not genetic, they think, we can take a peasant of any race and indoctrinate him with the the right propaganda and memorized procedures and he becomes as wise as anyone else could be.
The scientific forays made against the notion of heritable intelligence usually follow a two-step cycle: first, a scientific paper makes broad claims, and then, newspapers and media expand on these claims to make them absurdly broad. We can see this cycle in evidence through a Leftist attack on IQ:
These studies typically assume that the similarity of twins’ shared environment is the same as that of regular siblings (highly unlikely) and that adoptive families are as diverse as families generally (in fact, parents that adopt tend to be better off and better educated). When these assumptions are relaxed, environmental factors start to loom larger. In this regard, consider a pair of French adoption studies that controlled for the socioeconomic status of birth and adoptive parents. They found that being raised by high-SES (socioeconomic status) parents led to an IQ boost of between 12 and 16 points – a huge improvement that testifies to the powerful influence that upbringing can have.
A study of twins by psychologist Eric Turkheimer and colleagues that similarly tracked parents’ education, occupation, and income yielded especially striking results. Specifically, they found that the “heritability” of IQ – the degree to which IQ variations can be explained by genes – varies dramatically by socioeconomic class. Heritability among high-SES (socioeconomic status) kids was 0.72; in other words, genetic factors accounted for 72 percent of the variations in IQ, while shared environment accounted for only 15 percent. For low-SES kids, on the other hand, the relative influence of genes and environment was inverted: Estimated heritability was only 0.10, while shared environment explained 58 percent of IQ variations.
…Among the strongest evidence that IQ tests are testing not just innate ability, but the extent to which that innate ability has been put to work developing specific skills, is the remarkable “Flynn effect”: In the United States and many other countries, raw IQ scores have been rising about three points a decade. This rise is far too rapid to have a genetic cause. The best explanation for what’s going on is that increasing social complexity is expanding the use of the cognitive skills in question – and thus improving the opportunities for honing those skills. The Flynn effect is acutely embarrassing to those who leap from IQ score differences to claims of genetic differences in intelligence.
Unfortunately, they do not list the “pair of French adoption studies” but we can look at Turkheimer. I left in the paragraph about the Flynn effect for a good reason as well. First we should look at the abstract of that study which tells us what it really found:
Results demonstrate that the proportions of IQ variance attributable to genes and environment vary nonlinearly with SES. The models suggest that in impoverished families, 60% of the variance in IQ is accounted for by the shared environment, and the contribution of genes is close to zero; in affluent families, the result is almost exactly the reverse.
These are unusual results because they illustrate the heritability of IQ except in certain circumstances, namely when someone is of low socioeconomic status (SES). These are twin studies, so you have one twin who is kept in their original family SES conditions, while another is raised by someone who is not.
What they found is that twins from affluent homes score the same on IQ tests regardless of where they are being raised, but that for kids from poor homes, their IQ scores also rise. Where have we seen something like this before… oh, right, the Flynn Effect, which claimed that world IQ scores were rising:
Generational IQ changes (the Flynn effect) have been shown to be predominantly positive but differentiated according to IQ domains and countries. However, evidence from recent studies points towards a decrease of the Flynn effect globally or even a reversal in some countries…Our results suggest saturation and diminishing returns of IQ increasing factors (e.g., life history speed) whilst negative associations of IQ changes with psychometric g may have led to the observed IQ score decrease in more recent years.
One suggested reason for this possible IQ increase is a temporary decrease in brain damage due to lead:
The dramatic decrease in U.S. blood lead levels (BLLs) since the 1970s has been documented-however, the anticipated societal impact on intelligence quotient (IQ) has not…The dramatic societal decreases in BLLs in the U.S. since the 1970s were associated with a 4-5-point increase in the mean IQs of Americans. This effect is consistent with researchersâ€™ predictions; however, other variables (e.g., medical advances) may have contributed to the IQ gains.
Perhaps lead is only one of many factors. The Flynn Effect corresponded to a rise in worldwide nutrition, better health through antibiotics, and greater alertness of the world outside of small isolated areas. If the affluents kids do not experience loss when their environment is changed, but the poorer kids do, then perhaps their IQ gains are not gains but a lack of damage caused by environmental factors.
Important to note is that their gains did not pull them up to the level of the affluent kids. This fits with a pattern of reversing damage which retards them instead of changing the heritability of IQ; it seems that how most impoverished people live, or the choices they make, have effects similar to those of lead.
In other words, this study does not damage the heritability of IQ at all, but strengthens it. However, you will not read that in The Atlantic, but the exact opposite. As with all things Leftist, invest zero trust in them because their behavior is pathological arising from the need to accept untrue ideas (“equality”) as the basis of their understanding of reality.