Human Evolution May Explain Higher Rates of Autism
A new study published in Molecular biology and Evolution suggests a link between the evolution of the human brain and the prevalence of autism Spectrum Disorder (ASD). With approximately 3.2% of children in the US and roughly 1 in 100 children globally identified with ASD, scientists have long wondered why these conditions appear to be largely unique to humans, rarely observed in othre primates.
Recent advances in single-cell RNA sequencing have allowed researchers to map the diverse cell types within the brain and identify genetic changes specific to Homo sapiens. This new research focused on comparing brain cell evolution across mammals, specifically examining the rate of change in different neuron types.
The study revealed that L2/3 IT neurons - the most abundant type of neuron in the outer layer of the brain – evolved exceptionally quickly in humans compared to other apes. Intriguingly, this rapid evolution coincided with important changes in genes also associated with ASD.Researchers believe this suggests natural selection favored these genes in human ancestors,though the reason why remains a mystery.
While the exact benefits are unknown, the researchers speculate that these genes may be linked to slower postnatal brain advancement, a characteristic unique to humans. This extended development period coudl have fostered more complex thinking. Additionally, many of the genes involved are also connected to speech production and comprehension – abilities uniquely developed in humans and often impacted by ASD and schizophrenia.
“Our results suggest that some of the same genetic changes that make the human brain unique also made humans more neurodiverse,” explains lead author Alexander L. Starr. This research highlights the possibility that the very traits that drove human cognitive advancement may also contribute to the neurodiversity we see today.
