We are almost sure that genetics (and perhaps nutrition) are the main determinants of IQ. We won't have a complete answer until most of the genes that affect intelligence are found. With regard to your specific question of if educational attainment is the main factor in causing IQ to increase, that would mean that everyone at high-school would have the same IQ because they all have the same educational attainment (inasmuch as what "educational attainment" means in this paper). Wealth of one's parents is a harder problem. I believe that it is not a significant contributing factor beyond not being malnourished. This is based on the fact that the average IQ of some poor countries is higher than the average IQ of some richer countries. But like I said a complete solution to this problem, or – more boldly – an answer that blank-slatists would have no choice but to accept, would involve a more complete understanding of the genetic component including most genes as well as relevant ncDNA sequences.
Even if genetics is the "main determinant" what does that mean? Is it the the plurality of determinants? 51% correlation? 99%? Depending on the number, there's lots of room there for other factors.
I think you're oversimplifying with your example regarding educational attainment. The results say it's not a 1:1, so not all high school students would be marked the same, but it would mean that if you finished your post doc you're likely to score higher than someone who didn't complete grade 9. Would we argue that graduating high school or going on to do graduate work is simply as a matter of intelligence and not a more complex web of economic, social, and cultural factors?
I think you missed my point re. educational attainment. My point is that if education attainment only exists as a difference after high-school (for the most part). Therefore if "IQ follows educational attainment" IQ would be the same until after high-school. I do think wealth, nutrition and education have some effect on IQ. I do not know to what extent. You had asked if we are sure that IQ follows those other factors. To answer completely, IQ follows genetics as well as other factors, mainly genetics. I truly believe that this is a scientific question that can be answered with observation. I think in twenty years or less we will have cataloged most of the genes that affect intelligence and the nature vs. nurture argument will have a direct answer. (or, at least, the nature side of the equation will be mostly solved.) Currently the hardware to collect this data is expensive (Illumina machines are $1M last I checked) and the methods of analyzing the data are somewhat crude (eg. GWAS). As these two fronts advance more and more genes will be found until most of it is known.
My subjective impression from the correlation studies that I have seen is that the remainder largely is a long list of purely negative factors - i.e. in the "nurture" stage there are many ways to screw up the development of children with a large impact, but limited ways to meaningfully improve it over the genetic 'baseline'.
I.e. the correlation of nutrition in IQ is mostly driven by malnutrition, not by differences between great nutrition and mediocre nutrition; the impact of parenting is heavily driven by the outlier cases of severe abuse or deprivation, not the differences between great parenting and mediocre parenting, the impact of peer groups is largely set by the minority of cases that result in severe addiction or gang membership, not the difference between lousy friends and great friends, etc - that's the pattern that I seem to see there.
Do you have a source for that claim? Might you be misquoting a different popular statistic that g accounts for roughly have of intelligence between individuals? Or perhaps the figure that intelligence is about 50% heritable?[0] It is important to note that heritability of a trait and the extent to which a trait is genetically caused are not the same. It is possible for a trait to be eg. 80% caused by genetics and only 60% heritable, even on the average. This can be the case where the trait is defined by multiple genes (and non-coding DNA) where the proportion of the different genes matters and where specific combinations of genes are necessary. Also heritability of intelligence has been reported as higher than 75%.
The article may be conflating genetics with other types of biological hereditability, (such as epigenetics?) however I think that is generally pretty common and fine in every lay conversations.
If you control for socioeconomic status of the parents (which does have a big impact and definitely has to be controlled for, and is controlled for in every reasonable study), the socioeconomic status and educational attainment of the kids is still correlated with their IQ.
