Furthermore, I'd like to point out that even among those who consider IQ a valid measure and seek to use better methodology in measuring it, scholars are still unsure on how to interpret the cause and effects.
There are quite a few studies that show that IQ changing - eg. actually increasing over time: "We found [China's] FIQ increased by 6.19 points, PIQ by 6.55 points, and VIQ by 1.91 points." "In Japan, Lynn and Hampson (1986) reported an average gain of 7.7 IQ points per decade for samples born from 1940 to 1965."
https://www.sciencedirect.com/science/article/pii/S0160289613000901
Assuming they had a decent methodology, good sample size, and accounted for the huge ethnic and genetic variation in China (idk if they did or not), China basically went from average IQ/slightly below average IQ in the 1980s to above average IQ in the 2000s.
A 90s French study of 5000 children showed that IQ can greatly change over time. It included a study of 65 neglected children with an average IQ of 77 (borderline retardation) and showed that being adopted into better low socioeconomic families boosted their IQ to 85 when tested a few years later. The ones that got adopted into higher socioeconomic families boosted their IQ to 98.
"From 5,003 files of adopted children, 65 deprived children, defined as abused and/or neglected during infancy, were strictly selected with particular reference to two criteria: (
I) They were adopted between 4 and 6 years of age, and (
ii) they had an IQ <86 (mean = 77, SD = 6.3) before adoption. The average IQs of adopted children in lower and higher socioeconomic status (SES) families were 85 (SD = 17) and 98 (SD = 14.6), respectively, at adolescence (mean age = 13.5 years). The results show (
I) a significant gain in IQ dependent on the SES of the adoptive families (mean = 7.7 and mean = 19.5 IQ points in low and high SES, respectively), (
ii) IQs after adoption are significantly correlated with IQs before adoption, and (
iii) during adolescence, verbal IQs are significantly lower than performance IQs."
https://www.pnas.org/content/96/15/8790
"The French study, published Thursday in the journal Nature, found that children who were either born to, or raised by, parents of high socioeconomic status had IQs 12 to 15 points higher than children born to, or raised by, parents of low status. ..... "It really is nature and nurture," she said. Pierre Roubertoux, director of the University of Paris genetics lab where researchers Christiane Capron and Michel Duyme did their study, said the research is the first to show that children born to high-status parents but adopted by low-status parents have lower IQs than similar children adopted by high-status parents. That is one of the strongest pieces of evidence for an environmental effect, he said. "This has never been shown before..."
"While the study looked at only 38 adopted children, researchers in the field said its design allowed it to pick up a larger environmental effect on IQ than earlier studies. The children's average age was 14... Capron and Duyme found that adopted children who had been born to high-status parents had an average IQ nearly 12 points higher than children born to low-status parents, regardless of the status of the adoptive parents. This showed that biology plays a role in intelligence. But the study indicates that upbringing plays an important role as well. The researchers found that children adopted by high-status families had an average IQ more than 15 points higher than children adopted by low-status parents -- regardless of the status of their birth parents."
https://www.washingtonpost.com/arch...dy-says/59ed01e3-2489-4600-b405-18ba4dd71919/
I don't know how valid these tests are either...but it just goes to show that the academic community doesn't have a consensus on many many issues regarding IQs. If these studies are at least somewhat credible, then it supports the fact that IQ scores are influenced by genes but also heavily influenced by the environment. Which goes back into some of the criticism of how IQ is even calculated (many scientists are skeptical of the g value and its calculation) and how it is often misused to make the claim of "better genes."