Is IQ really related to fertility (or other things)?

Boutwell et al. (2013) examine the association between fertility rates and IQ on the county level in the United States. In doing so, they attempt to test Rushton's evolution-based "differential K theory", but ignore the fact that fertility rates have changed significantly even on the national level in recent decades (Wicherts et al. 2010). This suggests that they've been changing even more on the county level. They also ignore decades-old research suggesting that environmental factors can account for the race differences in fertility Rushton claims are due to genetic factors. As Weizmann et al. (1990, p. 6) noted, "Bean and Swicegood (1985) conclude that one can predict the birth rates of female minority group members from the educational attainments of their respective mothers (p. 21)." Zuckerman & Brody (1988) also noted that despite assumptions to the contrary by biological determinists, "there is no evidence that fertility itself is heritable."

Boutwell et al. (2013) state, in their introduction, that "IQ levels, for instance, correlate with gestation time during pregnancy (Rushton, 2004), disease rates (Templer & Rushton, 2011) and life expectancy (Lynn & Vanhanen, 2012)."

The first of these sources says NOTHING about IQ being associated with gestation period, and instead finds an association between an "r-k life history factor" that correlates with gestation period with a correlation coefficient of 0.86. What is most concerning is that this finding is based on "...a large data set of life-history variables on 234 mammalian species"--so it wasn't even based entirely, or even mostly, on humans!! Yet these "biosocial criminologists" are so desperate to make their point about IQ being the be-all and end-all in determining societal inequality, that they'll blatantly lie about what a source actually shows/says. 

So the Templer/Rushton source they cite for the "disease rates" thing did in fact report a positive correlation between a bunch of state-level variables, namely, "IQ, skin color, birth rate, infant mortality, life expectancy, HIV/AIDS, violent crime, and state income". Of course, as mentioned above, some of these variables have been changing a lot in recent decades, which casts doubt on evolutionary and/or IQ-based explanations thereof. As Wicherts et al. (2010) noted, "In much of the twentieth century, fertility and infant mortality rates have been much higher in China than in European countries. This is inconsistent with Rushton’s assertion that East-Asians are more K-prone than Europeans." 

As for the IQ-life expectancy relationship, the source they cite does indeed say that "All the correlations [between national IQs and health] are negative, showing that the populations of higher IQ nations are more healthy" (Lynn & Vanhanen 2012, p. 6). But the fact remains, this doesn't prove any kind of cause-and-effect relationship. As Wicherts et al. (2010b) noted, "Templer claims that the “potential of national IQs as explanatory variables” is demonstrated by correlations of national IQ with variables like GDP, adult literacy, and life expectancy. A glance at the correlation matrix in our primary paper shows that other variables associated with development have the same explanatory power as national IQ. For instance, the correlations reported by Templer (2008) are easily replicated by replacing national IQ with Proteins g/day/capita, child mortality rate, or secondary school attendance. This means that these variables have just as much explanatory power as does national IQ." There's also, of course, the potential for the ecological fallacy to affect any relationships found in this type of research (e.g. Ellison, 2007).

Addendum: Boutwell et al. (2015) claim that "Rushton's (1985a) application of life history theory to human differences has fared well at organizing the correlations of a host of human outcomes into a coherent evolutionary framework (Figueredo et al., 2006; Nettle, 2010; Rushton, 2000; Wang, Kruger, & Wilke, 2009)." Hoo boy, let's break this down. 

So Figueredo et al., 2006 does say that "A number of independent literatures consistently describe a positive manifold of correlations among many common human behavioral traits considered “social problems.” Theories derived from the Standard Social Science Model do not fully account for this positive manifold or cluster of “social problems,” but Life History Theory does because it instead construes such clusters to be coordinated arrays of contingently adaptive life-history traits." So that checks out, though this claim that you can't explain it without invoking evolutionary biology seems rather fishy--correlation is not causation, and these factors could certainly be related without any biological factors involved.

Nettle, 2010, however, doesn't even mention Rushton or his theory at all, nor does Wang, Kruger, & Wilke, 2009.

Rushton, 2000 is Rushton's own book, hardly a reliable or independent validation of his theory.

Later on, we see "Although our evolutionary history has placed us as a species on the K end of the life history spectrum, natural variation is expected to position some individuals further from K than others (Rushton, 2000). Individuals falling relatively further from K will exhibit faster maturation and lower levels of parental investment (Rushton, 1985a). Additionally, they will display greater mating output (i.e., more effort invested in mating, instead of raising children), higher rates of disease and shorter life spans (Rushton, 1985a, 2000, 2004)."

Truly, it is absurd that they keep citing Rushton's work uncritically without even mentioning any critiques of it.
Sources:
Boutwell et al. (2013): http://www.sciencedirect.com/science/article/pii/S019188691300189X
Boutwell et al. (2015): http://www.sciencedirect.com/science/article/pii/S1359178915001184
Ellison (2007): http://onlinelibrary.wiley.com/doi/10.1348/135910707X180972/full
Lynn & Vanhanen (2012): https://www.ttu.ee/public/m/mart-murdvee/EconPsy/2/Lynn_Vanhanen_2012_National_IQs_-_a_review.pdf
Templer & Rushton (2011): http://philipperushton.net/wp-content/uploads/2015/02/IQ-Skin-Color-Crime-HIV-AIDS-and-Income-in-50-U.S.-States-2011-by-Donald-I.-Templer-John-Philippe-Rushton.pdf
Weizmann et al. (1990): http://philipperushton.net/wp-content/uploads/2015/02/iq-race-brain-size-r-k-theory-rushton-weizmann-canadian-psychology-1-1990.pdf
Wicherts et al. (2010): http://www.sciencedirect.com/science/article/pii/S0191886909002475
Wicherts et al. (2010b): http://www.sciencedirect.com/science/article/pii/S0191886909003675
Zuckerman & Brody (1988): http://www.sciencedirect.com/science/article/pii/0191886988901365