Autism spectrum disorder (ASD) now affects about one in 31 children, or 3.2%, in the U.S.—up from just 0.6% in the early 1990s. Our new study, published in the journal Molecular Biology and Evolution, revealed that their fears were unfounded. It provides new clues to the potential biological factors that might explain this striking prevalence. Led by Alexander L. Starr and his colleagues, the research focuses on the evolution of neurons and identifies a specific neuron type that has accelerated in humans, which may be linked to increased rates of autism.
We leveraged cross-species single-nucleus RNA sequencing datasets. These datasets were derived from three very different areas of the mammalian brain, which likely contributed to our findings. By taking these datasets and comparing them, the researchers hoped to gain a greater understanding of how neuronal evolution may play a role in neurodiversity, especially in humans.
Uncovering Neuronal Evolution
The research introduces a new radical concept of neuronal evolution. More importantly, it underscores the ways in which particular genetic mutations have distinguished the human brain from that of all other mammals. As social scientists and practicing clinicians, we believe that this differentiation contributes to the underdiagnosis of neurodevelopmental conditions. The classic example of this kind of condition is autism.
Starr emphasized the significance of their findings, stating, “Our results suggest that some of the same genetic changes that make the human brain unique made humans more neurodiverse.”
The research underscores the complexity of autism, illustrating that it is not solely a disorder but rather part of the broader spectrum of human neurodiversity. The study explores the development of the various types of neurons. Here, 14 years later, it offers a new way of looking at how these developments might have influenced the traits associated with autism.
Methodology of the Study
Starr and his team used the latest RNA sequencing methods to assess single nuclei from multiple brain regions. To reach these conclusions, they zeroed in on specific species across the mammalian tree. The datasets were intentionally chosen to best showcase evolutionary differences and similarities between complex and simple neuronal structures.
This strategy helped the researchers to pin down particular types of neurons. These neurons have evolved greatly in humans as compared to other mammals. Knowing these evolutionary adaptations will be key. In doing so, it advances our knowledge of the biological underpinnings of autism and the ways it presents in human populations.
Starr et al. produced a remarkable analysis that greatly enriches our understanding of neuronal evolution. Their findings open new doors for understanding genetic factors that underlie the development of autism more broadly. The possible implications from this study could result in greater awareness and understanding of neurodevelopmental disorders, as well as their rising prevalence.
Implications for Understanding Autism
The results from this study should open doors for novel pathways to be explored in the study of autism and other related disorders. By pinpointing a human-accelerated neuron type, researchers can investigate the genetic mechanisms that lie at the heart of ASD. The research underlines the need for further investigation into evolution’s role. Its evolutionary interactions have allowed it to not only mold brain structure but behavioral diversity as well.
As ASD goes on to impact more and more people, especially children, knowing where it all started is more important than ever. The unexpected relationship between neuron evolution and autism prevalence provides a novel framework to understand the impact of genetic changes on human neurodevelopment.
The research paper titled “A General Principle of Neuronal Evolution Reveals a Human-Accelerated Neuron Type Potentially Underlying the High Prevalence of Autism in Humans” is available for access online, including its DOI, 10.1093/molbev/msaf189.