What Is Intelligence? An Unprecedented Genetic Discovery

Few things appeal to scientific interest as much as intelligence, a difficult to define (yet intuitively grasped) concept that constitutes an intrinsic part of what it means to be human. The genetic and neurological breakthroughs in the 20th century have enabled scientists to investigate the roots of intelligence with unprecedented depth and details. But most efforts to decipher the genetics of intelligence have been unproductive given the complexity of the subject. The recent work from Dutch scientists has brought new light to the enormous genetic complexity behind intelligence. In this breakthrough, more than 50 genes—40 of which were previously unknown—have been associated with the development of the intelligence traits. The work is published in the journal Nature Genetics.

Much of the scientific and philosophical debate about intelligence is centered on how much of it is genetically inherited or environmentally induced. Scientific efforts have been largely inconclusive in this regard, and, until now, only a handful of genes had been implicated in the development of intelligence. Currently, the preliminary consensus based on statistical observation is that the aspect of intelligence defined as IQ is a genetically inherited potential stimulated by the environment. It is believed that the genetic factor of IQ gains weight as people age. The exact mechanisms behind this process remain poorly understood. An unprecedented discovery at the Vrije Universiteit Amsterdam, Netherlands, is a large step forward in the effort to understand the true nature of intelligence.

The massive meta-analysis revealed solid associations between several genetic markers, which could help scientists better understand how everything is intertwined at the genetic and neurological level. Researchers analyzed data from more than 70 thousand people of European descent, running statistical analysis and extensive genetic mapping. The meta-analysis revealed that most of the newly implicated genes have strong expression on brain tissue. Danielle Posthuma's team observed significant correlation between the genes implicated in intelligence and the genetic associations with education, height, intracranial volume, and even head circumference in childhood. Inversely, they found a negative correlation between intelligence and BMI, Alzheimer's disease, tobacco smoking and even waist-to-hip ratio.

Ironically, the main takeaway from this study is that intelligence is even more complex and difficult to reverse engineer than previously thought. Despite the large number of new genes discovered, and their solid associations with aspects of health and well-being, researchers affirm that these account for no more than 5% of the variation in human intelligence.

This is the largest research effort on this subject to date, and it undermines the increasingly common conjecture that the expression of intelligence is defined by only a handful or even a single gene. So the fears of future intelligence-guided eugenics may be put aside, at least for now.