It's not Tylenol: Researchers discovered that autism's prevalence may be linked to human brain evolution.

Researchers discovered that autism’s prevalence may be linked to human brain evolution. Specific neurons in the outer brain evolved rapidly, and autism-linked genes changed under natural selection. These shifts may have slowed brain development in children while boosting language and cognition. The findings suggest autism is part of the trade-off that made humans so cognitively advanced.

A new paper in Molecular Biology and Evolution, published by Oxford University Press, finds that the relatively high rate of Autism-spectrum disorders in humans is likely due to how humans evolved in the past.

About one in 31 (3.2%) children in the United States has been identified with Autism Spectrum Disorder. Globally, the World Health Organization estimates that around one in 100 children have autism. From an evolutionary perspective, many scientist believe that autism and schizophrenia may be unique to humans. It is very rare to find behaviors associated with the disorders in non-human primates. In addition, behaviors associated with those disorders generally involve cognitive traits like speech production and comprehension that are either unique to or much more sophisticated in humans.

With the development of single cell RNA-sequencing, it became possible to define specific cell types across the brain. As investigators published more large-scale datasets, it became clear that the mammalian brain contains a staggering array of neuronal cell types. In addition, large-scale sequencing studies have identified extensive genetic changes in the brain unique to Homo sapiens -- genomic elements that did not change much in mammalian evolution in general but evolved rapidly in humans.

https://www.sciencedaily.com/releases/2025/09/250927031224.htm