Are the Genes Associated with Human Cognitive Function Conserved Across Species that Exhibit Fluid Reasoning and Spatial Cognition, and What Does the Pattern of Conservation Reveal About the Evolution of Intelligence?

The study seeks to determine whether genes associated with human cognitive function have been conserved in other species, and what the pattern of conservation reveals about the evolution of intelligence. The study uses 350 genes obtained from the intersection of the Davies (2018) and Savage (2018) Genome-Wide Association Studies related to general cognitive function. It then tracks their orthologs across nine other species, spanning more than 600 million years of evolutionary divergence, and finds that human cognitive genes were significantly more conserved than the genome average in every species tested. The paper has tested whether the human cognitive genes overlap with independently compiled gene sets of the mouse, fruit fly, and mountain chickadee. This was conducted using hypergeometric tests against a background of 23,262 human protein-coding genes. The research has found that the human, mouse, and fly cognitive genes overlapped much more than the genome average. However, the chickadee gene set shared no genes with the other three sets and the absence of overlap was not statistically significant. The gene ontology enrichment analysis identified 56 pathways that were independently enriched across all three species, a convergence that permutation testing confirmed exceeds chance. However, functional annotation showed that only 6.2% of conserved mouse orthologs and 3.5% of conserved fly orthologs have documented cognitive roles, showcasing that sequence conservation does not necessarily imply functional conservation. The results of the study support the theory that an ancient molecular toolkit for learning and memory is shared across most animals. However, the selection for cognitive ability across different lineages can act on different genes.