>> Is this settled science, one person's hypothesis, or something in between?
> 3. Something in-between
Much appreciated (all of your answers). If someone has knowledge of where this falls on the continuum of #3, it would help those of us outside the field understand how much credibility we should give to this article.
I can't speak for the GCTA method, but the five main findings discussed in the review have all been known within the field for years: this is a review, rather than a research article.
If these findings are surprising to you, it is because there is probably no greater gap between lay and expert opinion than on the subject of intelligence. The psychological study of intelligence has a poor reputation among the lay public primarily due to the perception that it might support unsavory political conclusions. Hence, psychometric research must be intrinsically flawed crackpottery. In truth, the correlations between IQ and various life outcomes exceed practically any other effect observed in social science. Further, we have as much reason as we ever could have in social science--from a variety of sources all pointing in the same direction--to suspect that the causal arrow points from intelligence to good outcomes.
I encourage you to look into the issue for yourself, but my synopsis is that the picture one gets from the literature is unrecognizably different from the picture one gets from non-specialist media.
> 3. Something in-between
Much appreciated (all of your answers). If someone has knowledge of where this falls on the continuum of #3, it would help those of us outside the field understand how much credibility we should give to this article.