This is an interesting paper, but I note it refers to European populations. It may not hold true of societies in which many children are the product of older men accumulating many younger wives.
PATERNAL AGE AS AN INDICATOR OF NEW MUTATIONS: CHILDREN OF OLDER FATHERS HAVE LOWER EVOLUTIONARY FITNESS, BUT NOT LOWER INTELLIGENCE
Ruben C. Arslan 1 , Kai P. Willführ 2 , Emma M. Frans 3 , Mikko Myrskyla 4 , Catarina Almqvist 3 & Lars Penke
1 Georg August University Göttingen, Germany, email@example.com.
2 MPI for Demographic Research, Rostock, Germany.
3 Karolinska Institut, Stockholm, Sweden.
4 MPI for Demographic Research, Rostock, Germany.
Paternal age at offspring conception seems to be the main driver of single nucleotide de novo mutations (Kong et al.., 2012). Different theories posit that intelligence is linked to mutation load as a fitness indicator or simply owing to its genetic complexity. Based on evolutionary genetic theory we predicted negative paternal age effects on offspring fitness and intelligence in the normal range. To investigate effects on fitness, we used church records from three pre-industrial Western populations and governmental data from 20th century Sweden. We used a sibling control design and accounted for confounds including maternal age, birth order and parental loss. Main analyses had an aggregate N > 1.3 million.
To investigate effects on intelligence, we compared siblings in the German Socio-Economic Panel (N = 1479). Furthermore we were the first to directly adjust for measured parental intelligence, the most obvious confound, in data from the Minnesota Twin Family Study (N = 1898 twin pairs). We found clear support for mutational paternal age effects on offspring survival, mating and reproductive success. Weaker effects were found in 20th century Sweden, possibly indicating a diminished strength of purifying selection. However, we found no mutational paternal age effect on offspring intelligence, which was corroborated further by a Swedish study of half a million men (D’Onofrio et al.., 2014).
Although paternal age effects seem to be an appropriate way to characterize the effect of de novo mutations on fitness, no effect was found on intelligence in the normal range. Genomic research supports this result. The inferred genetic architecture of intelligence does not seem to make it fragile and vulnerable to increases in paternal age-driven mutation or to decreases in purifying selection.