> Ten years from now we’ll have tests that come within a narrow margin of error of predicting IQ from spitting in a test tube. Modulo malnutrition and serious physical abuse but the first at least is not common in the developed world.

Malnutrition and serious physical abuse aren't the only environmental factors with a known significant impact on intelligence, and nutrition (particularly childhood nutrition) patterns with a serious adverse effect on IQ have been identified in research focussed on first world areas of study; they certainly aren't rate enough to be insignificant sources of variation in the first world.