Intelligence can be attributed to the overall effect of a multitude of genes passed down from parents, as well as the socio-economic environment in which one grows up.

Genetic research indicates that about half of the differences in intelligence can be attributed to differences in our genetics, but intelligence is also dependent on external factors. The environment, socio-economic, and health conditions can play a big role in our intelligence.

The genetics of intelligence is a complicated topic. Scientists still do not fully understand it. In a 2017 study conducted in the UK on over 78,000 individuals, 40 new genes were identified to be associated with intelligence. Similarly, there might be thousands of gene variants responsible for one’s intelligence, which are passed down by both parents. Scientists continue to study and gather updated information about this complex system.

Older, outdated research found important intelligence genes on the X-chromosome. Females have two ‘X’ chromosomes (XX) and males have an X and a Y chromosome(XY). While the X-chromosome has been shown to be linked to brain development, that does not equate to intelligence. No recent studies have found key intelligence genes on the X-chromosome explicitly.

For a few years now, some social media articles have been claiming that “intelligence genes” are inherited only from the mother.  This claim may be based on the misinterpretation of a study conducted more than a decade ago. Moreover, the study was conducted to understand a different topic altogether: it measured the effect of maternal intelligence, through breastfeeding, on the intelligence of children. The father’s intelligence was not part of the study. 

Another study used to substantiate this misleading claim includes an experiment conducted on mice in the 1990s and does not translate well as evidence in humans. Importantly, not all mice experiments translate into human behavior and may not be enough evidence to substantiate human psychology.