Human Evolutionโ May Explain Higher Rates of Autism
A new study published inโค Molecular โbiology and Evolution suggests a link between the evolution ofโ the โคhuman brain andโค the prevalence of autism Spectrum โคDisorder (ASD).โ With approximately 3.2% of children in the US and roughly 1 in โ100 children globally identified with ASD, scientists have โlong wondered why these conditions appear to beโ largely unique to humans, rarely observedโ in othre primates.
Recent advances in single-cellโ RNA sequencingโ have โallowed researchers to map the diverse cell types โwithin the brain and identify genetic changes specific โtoโ Homo sapiens. This โnew research focused on comparing brain cell evolution across mammals,โค specifically examining โฃthe rate โคof change in different neuronโ types.
The โขstudy revealed that L2/3 โขIT neurons โ-โ the โฃmost abundant โtype of neuron in the outerโฃ layer of the brain – evolved โexceptionally quickly in humans compared toโ other โฃapes. โ Intriguingly, this rapid evolution coincided with important changesโ in genes also associated with ASD.Researchersโฃ believeโ this suggests natural selection favored these genes in human ancestors,though theโ reason why remainsโ a mystery.
While the exact benefits are unknown, the researchers speculate that these genes may โคbe linked to slower postnatal brain advancement, a characteristic uniqueโ to humans. This extended development period coudl have fostered more complex thinking. Additionally,โ 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 โof the same genetic changes โคthat 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 โฃthat drove human cognitive advancement may also โcontribute toโ the neurodiversity we see today.