Although there are exceptions to the rule, taller people generally have a higher IQ. It's all in the genes, but both height and intelligence are highly complex traits, which aren't down to just single genes, but a whole raft in combination. So why are they linked? It's all to do with sex and your parents, although hopefully not both at the same time.
It's been hypothesised and statistically tested for a while, that the reason taller people are more intelligent is because both traits are attractive and therefore selected for in mating. Simply put, attractive intelligent people who are tall, pop sprogs with other people who are intelligent and tall, creating a self-reinforcing loop of tallness and intellect.
A new, more advanced study has shown that, while sexual selection certainly plays a part, the additive effects of genes associated with height and intelligence could also play a crucial role. By additive, I mean that some of the genes associated with a tall height will also play a role in intelligence, and visa versa. It's technically called pleiotrophy, where one gene affects multiple traits.
As both height and intelligence are highly heritable traits -- passed down from your parents to you and your siblings -- the genetic reinforcement of both pleiotrophy and sexual selection means that you'll likely have a similar height and intelligence to your parents, which is what you'd expect.
However, precisely how much pleiotrophy has an affect on your intelligence and height is unknown. More research is certainly required, probably through interrogation of large data sets using clever statistical methods, but at some point in the near future we might be able to pinpoint the genetic traits that make you both smart and tall. At that stage, we might even be able to select for them, which is both an amazing and scary thought -- what if we all ended up being monstrously tall and incredibly intelligent? [PLoS Genetics via Discover]
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