What are the risks facing the children of older fathers?
Older fatherhood has typically been associated with bad news, in spite of the benefits perhaps of wisdom. Regardless, advanced paternal age (APA) is associated with higher risk for autistic spectrum disorders and schizophrenia, notably. In my experience, older parents are sometimes more concerned with longevity and being less energetic or hip than their younger parent peers.
So it wasn't surprising that I found "Advanced developmental outcomes of advancing paternal age" in the journal Translational Psychiatry (Janecka et al., 2017) of note. These researchers analyzed data on over 12,000 twins in over 6,000 families in the TEDS (Twins Early Development Study) sample, seeking to understand whether advanced parental age conveyed any benefits. They developed a validated measure called the "Geek Index," and hypothesized that advancing paternal age is associated with a higher GI.
Why is this an important question? For one thing, there are the aforementioned oft-cited statistical downsides to older paternal age. Autism is more and more common, and represents parenting challenges as well as rewards (read Harmony, a revealing fictionalized account the ups and downs of raising a child with autism). There is the issue with mortality and wanting live longer and more energetically to be around for one's kids and grandkids, as well as to enjoy life in other ways. Many older parents, for example, express guilt about being older—and I've come across critical statements about people who have children when they are older, in addition to less judgemental perspectives highlighting the many advantages of being an older parent.
The benefits of waiting to have children
But younger parental age is also associated with negative outcomes, attributed to, on average, having less education and less money and resources in general. Their children have been shown, again on average, to be at greater risk for low achievement, criminal activity, drug and alcohol abuse and health issues. Older parents, on the other hand, may be more "fit" (in the evolutionary sense), given the tendency toward accomplishing more before having children. In terms of evolution, what is fit today is very different from what was fit even a few hundred years ago—especially given the dominance of technology and science in our world—let alone millions of years ago.
The "Geek Index" and achievement
Because there is so little research in the area, it made sense to look at whether older age fathering conveys advantages, and if so how much is environmental and how much genetic. The study authors developed the Geek Index, correlated it with educational achievement between assessments at ages 12 and 16, and analyzed the relative contributions of environment and heredity.
The Geek Index is a derivation from measures of non-verbal intelligence, restrictive and repetitive behaviors, and social aloofness. The measures used to make up the GI are subscales from standard assessments used in the TEDS sample. These traits tend to overlap with autistic traits, but the study controlled for the presence of actual autistic spectrum conditions.
Educational outcome measures were taken from results on the GCSEs (General Certificate of Secondary Education), standardized national exams used in the UK. Researchers looked at subjects in the STEM (science, technology, engineering and mathematics) domains as well as in the arts and humanities so that they could tell whether there was a differential effect in different subjects by looking at performance as well as number and category of examinations taken within the GCSE. High STEM scores have been shown to predict future income and superior school performance, and are associated with long-term professional success.
Given the direction our culture is heading, there is ever-growing opportunity for people who are good with tech and science, in all its lucrative and transformative incarnations. We may worry our kids are too tech-focused, and we may want them to be more well-rounded and socially-oriented, but we also want them to make enough money when they grow up so they can feel safe and secure, free from worry about insufficient resources. Of course, there is more to success than money and more to a well-lived life than worldly success, but in the face of an uncertain future, we want kids to have the edge.
In terms of their findings, first they showed that the Geek Index is valid, correlating well with academic performance at age 16. Furthermore, the GI positively correlated with the specific subscales on the GCSE tied to higher future income. Having all three of the GI traits together (non-verbal cognitive measures, repetitive restrictive behaviors, social aloofness) correlated with higher IQs among teens taking more STEM examinations but not those taking more Arts exams. This was only true when all three traits were present, but not for combinations of two traits, or only one. This last finding tells us that the GI predicts greater STEM achievement if and only if the traits cluster together, lending further support for the utility of the GI.
Do the children of older fathers benefit?
In terms of the big question—are there geeky positives to older age fathers—the answer, according to this study, is yes. But only for sons. This sex difference was a very robust finding, particularly because it was a twin study, powered to study differences between identical and fraternal twins. However, it does not mean that there aren't any girl geeks (or other sexed geeks)—just that some of that geek goodness is passed from father to son. In addition, there was no significant correlation with maternal age on GI outcomes.
When they looked at nature-nurture balance, they found on average a 57 percent genetic inheritance and a 43 percent environmental loading. (They did not examine epigenetic effects, but that would be cool to include in future studies now that the GI is validated.) Even more fascinating, the data showed that the older the fathers were, the greater was the genetic variance correlating with GI—but not environment. This is interesting because we know that the rate of mutation is higher with older fathers, and associates with greater geekiness. On the other hand, somewhat counterintuitively given the "more experienced parent is better" hypothesis, environmental factors stayed the same for older and older fathers.
These are important findings because they support the notion that in addition to the risks of higher autistic spectrum traits, the same traits in less severe form are nowadays evolutionarily adaptive. And previous studies have showed that such traits are higher in professional groups including academics, musicians and engineers, and that common variants of autism are associated with higher IQ. The authors point out that the benefits of having a high GI are "likely to be specific to the modern knowledge-based environment, without necessarily having such advantageous effects historically... and the offspring of older fathers are not [therefore] inherently biologically 'fit.'"
This is a ground-breaking study on many levels. First, it introduces the Geek Index, which just sounds cool. There's certainly a lot more to the puzzle, and other relevant research on other parent-child interactions we haven't looked at here, in addition to clarifying the effect of gender. Having a tool to study geek effects is useful, and hopefully will bear fruit, possibly helping to elucidate gender differences by furthering the understanding of both heredity and environment.
Second, the study clearly shows that there are benefits to having older fathers, which appear related to context-dependent evolutionary fit. No doubt, there was that odd caveman who was good at tool-making, but stereotypically speaking he was in the minority compared to the brawny types who ran around hunting and gathering. Surely those hearty and hale fellows were grateful to have a sharper spearhead, or a better fishnet, and other ways to make life in general, and procuring food in particular, more efficient.
And fire... don't forget fire, the control of which was a primal technological advance, crucially in terms of how much faster it is to eat cooked food. So, was Prometheus a Geek God? Are "dad jokes" a good thing, after all? Intelligence trumped brawn because making obtaining and consuming food easier saved a lot of time and paved the way for further brain development, which in turn created more time and brain power to further fuel soaring technological development, and so on. Movies such as Revenge of the Nerds and The Croods poke at this evolutionary divide between wimps and jocks, and the prominence of powerful corporate geeks in recent history cannot be ignored.
Recognizing such age-related effects on offspring will help us better understand the impact that our rapidly changing world is having on our own evolution, and will contribute to understanding and refining our educational systems, especially when it comes to designing the best environment for children with high GIs.
Janecka M, Rijsdijk F, Rai D, Modabbernia A and Reichenberg A. (2017). Advantageous developmental outcomes of advancing paternal age. Translational Psychiatry 7, e1156; doi:10.1038/tp.2017.125