In development, timing is of the utmost importance, and the timing of developmental processes often changes as organisms evolve. In human evolution, developmental retardation, or neoteny, has been proposed as a possible mechanism that contributed to the rise of many human-specific features, including an increase in brain size and the emergence of human-specific cognitive traits. We analyzed mRNA expression in the prefrontal cortex of humans, chimpanzees, and rhesus macaques to determine whether human-specific neotenic changes are present at the gene expression level. We show that the brain transcriptome is dramatically remodeled during postnatal development and that developmental changes in the human brain are indeed delayed relative to other primates. This delay is not uniform across the human transcriptome but affects a specific subset of genes that play a potential role in neural development.
Here are the 4 classes of gene expression trajectories they’re focusing on: They found that there was a relative enrichment of genes which exhibited human neoteny, with delayed expression: Finally:
We analyzed the genes affected by the neotenic shift in the human prefrontal cortex with respect to their histological location, function, regulation, and expression timing. First, with respect to their histological location, we used published gene expression data from human gray and white matter…and found that, in both brain regions, human neotenic genes are significantly overrepresented among genes expressed specifically in gray matter…but not among genes expressed in white matter….
They found that there was a relative enrichment of genes which exhibited human neoteny, with delayed expression: