The HAR1F RNA gene is expressed by Cajal-Retzius brain cells which regulate how the six layers of the cortex develop in the human embryo. The cortex is reponsible for many complex brain functions including language and information processing. The HAR1F gene switches on in the human fetus seven weeks after conception then shuts down at 19 weeks. This gene experienced an atypical 18 mutations in humans during the last few million years. Meanwhile, over the last 200 million years, other mammal genomes such as the chimpanzee, gorilla, orangutan, and macaque had no such mutations. Could this HAR1F gene be somehow connected to the Stoned Ape Theory?

The receptor that psychedelic drugs target (the Serotonin 2A receptor) helps regulate the production of a molecule called Brain-Derived Neurotrophic Factor (BDNF, for short). BDNF helps regulate neurogenesis and neuroplasticity. Using genetic techniques to increase BDNF expression can enhance neurogenesis in certain brain regions as well. Activate the receptor, and the brain secretes more BDNF. Psychedelic drugs can enhance learning and memory capabilities by, at least partially, increasing the amount of BDNF (and related growth-factors) in the brain through activation of the Serotonin 2A receptor. 

Neurogenesis in the hippocampus may be a key part of the acquisition of new behaviors and pattern recognition. The balance of evidence suggests that exposure to psychedelics can, in fact, enhance neurogenesis in this region.  

In 2016, the Beckley Foundation, working with scientists at the Sant Pau Institute for Biomedical Research in Spain announced findings that two of the key components in Ayahuasca, harmine and tetrahydroharmine stimulate the differentiation of stem cells into healthy neurons.

In 2013, a group of scientists published the results of their experimental brain research using psilocybin (PSOP). Their report was titled, "Effects of psilocybin on hippocampal neurogenesis and extinction of trace fear conditioning." In the abstract, they concluded -- "PSOP facilitates extinction of the classically conditioned fear response, and this, and similar agents, should be explored as potential treatments for post-traumatic stress disorder and related conditions." 
Full Report Available from: Researchgate