How much of intelligence is inherited?
December 9, 2016 Neuroscience, Podcast 2 Comments

Episode 158

How much of your intelligence is inherited?  Which is more important: nature or nurture?  Smoking during pregnancy results in dumb babies…  right?

We answer all these questions and more in Episode 158.  Geoff Der, Senior Research Fellow at the University of Glasgow, joins Jesse to talk about the genetic link between parental intelligence and children’s cognitive development.

Nature vs Nurture

It’s an old debate, and one that won’t be entirely settled here.  But Der’s research can shed some light.

Probably the most striking finding from crunching huge amounts of data (we’re talking millions of data points here) is that many of the maternal behaviors we thought caused decreased intelligence, don’t.  Instead, it’s the mother’s own intelligence (or lack thereof) that is passed on to her offspring.

Example:  women who smoke while pregnant have children with impaired cognitive ability. But is it the smoking that causes this drop?  Or are less intelligent women more likely to smoke, and then pass on those genes to their kids?

We’re about to turn conventional wisdom on its head.  After crunching the numbers, it turns out that at least half of the variation in cognitive outcome is due to the mother’s own intelligence, not the smoking.  What’s more:  maternal education level completely accounts for the relationship between smoking during pregnancy and the child’s cognitive ability.  Once you take education level into account, there is no statistical significance between maternal smoking and cognitive ability.

The same thing applies to birth weight — two-thirds of the correlation between birth weight and later intelligence is explained by the mother’s own level of intelligence.

And again to breastfeeding.  When researchers looked at sets of twins where one twin was breast fed and the other wasn’t, there was basically no connection between breastfeeding and intelligence.  Of course, this is assuming non-breastfed babies are getting high-quality, sterile formula.

What About Dad?

Unfortunately, we don’t have much data on the paternal intelligence connection.  Partially this is because researchers haven’t collected as much data, and partially because it’s more difficult to be certain that a given guy is the biological father who contributed genetic material.

Live Long and Prosper

Another interesting connection in the data is that between early life intelligence and a longer life.  It’s more or less an upward-trending linear line: the smarter you are, the more likely you are to live a long life.  You’re both less  likely to die of external causes of death (murder, car accidents, etc.) and internal causes of death (cardiovascular disease, etc.).

Interestingly, there’s only one internal cause of death where the correlation does not apply, and that’s cancer.  There is one exception to this exception:  lung cancer.

PS:  It’s too late to be born to a smarter mom, but it’s not too late to make the most of what you were born with by signing up for our newsletter.

Written by Hannah Sabih
Hannah believes there's nothing 8 hours of sleep and some kale can't cure (yes, she's from California). She's an avid runner, reader, and traveler, who brings you the latest and greatest in neuroscience via our social media channels.
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