Intelligence: a mishmash of genetic ingredients

Like father like son. We have all heard it one time or another. The layman explanation to hereditary characters. Whether the cause is genetic inheritance or the effect of growing up in a certain environment, is quite something else. When talking about the origin of intelligence, there are always discussions. Even though there is undoubtedly an environmental component (socioeconomic factors, culture, language, family interactions…) it is widely acknowledged that intelligence is a strongly influenced genetic trait. Despite having a complex inheritance pattern, since there is no single intelligence gene, a recent meta-analysis ¹ on more than 78.000 people has been used to characterize better the genetic landscape of intelligence.

By means of genome-wide association studies (GWAS) on intelligence, the researchers compiled a list of genetic variations that correlated with intelligence levels. In spite of the wealth of intelligence tests available, the authors employed Spearman’s g, a measure of general intelligence independent of the specific test used to characterize it.

As a result of their meta analysis, they identified more than 300 SNPs (single nucleotide polymorphism, that is genetic variations within a gene of only one letter. For example, C to G, or A to T) in 18 genomic locations, about the half of those SNPs are located within a gene (in up to 22 genes), which might lead to protein changes. Moreover, they got to identify 29 new genes implicated in intelligence.

Of all those new genes, the majority were found to be expressed in brain tissue, while functionally many of those genes would be implied in cell development regulation. On the other hand, they could show a significant genetic association with certain neuropsychiatric (negative association to Alzheimer’s and depression/anxiety of schizophrenia; positive with autism) and metabolic disorders (negative association to waist-to-hip ratio; positive with intracranial volume)

In conclusion, this work represents a step forward in mapping and understanding the molecular signatures behind human intelligence. However, even considering this huge step forward in the genetic characterization of intelligence, we are far from being able to create a super brain. Sorry, Scarlett Johansson, your character in Lucy is still a dream…or a fake?