Genetic Changes in the Human Brain and Autism

Autism Spectrum Disorder (ASD) is a part of global health challenges, with studies indicating that approximately 3.2% of children in the United States are affected by this disorder. The World Health Organization estimates that one in every 100 children worldwide suffers from it. This disorder has sparked the interest of scientists aiming to understand its origins and development, especially given the belief that autism and schizophrenia might be unique to humans.

Genetic Changes in the Human Brain

With the advancement of single-cell RNA sequencing technologies, it has become possible to accurately identify different cell types in the brain. Studies have revealed an astonishing variety of neuronal cell types in the mammalian brain. Importantly, extensive research has uncovered large-scale genetic changes in the brain that are unique to humans, having evolved rapidly compared to other lineages.

Research has shown that some cell types have remained stable through evolution more than others, but the factors driving these differences in evolutionary speed remain unknown. To this end, researchers have analyzed RNA sequencing datasets from different regions of the mammalian brain.

Rapid Evolution of Specific Neuronal Types

Among the notable discoveries in this research is the rapid evolution of L2/3 IT neuron types in humans compared to other primates. Surprisingly, this rapid evolution was accompanied by dramatic changes in genes associated with autism, which appear to have been driven by natural selection specific to the human lineage.

Although the findings strongly suggest natural selection for autism-related genes, it is unclear why these genes were considered beneficial to human ancestors. One possibility is that these genes are linked to delayed development, which may have contributed to the slower postnatal brain development in humans compared to chimpanzees.

Language and the Evolution of the Human Brain

Interestingly, the ability to produce and understand language, a trait unique to humans, is often affected by autism and schizophrenia. These advanced linguistic capabilities may have been part of the factors that provided human ancestors with an evolutionary advantage. The rapid evolution of autism-related genes might have added the ability to develop language or slowed postnatal brain development, allowing for more complex thinking.

Thus, the slow brain development during early childhood may have contributed to the evolution of complex intellectual skills in humans.

Conclusion

Recent studies suggest that some genetic changes that make the human brain unique have also contributed to increased neural diversity in humans. Understanding these deep evolutionary processes can help clarify how intellectual and linguistic capabilities evolved in humans and why certain autism-related genes were naturally selected in our evolution. This research opens new avenues for a deeper understanding of the relationship between genetic evolution and humans’ unique mental capabilities.