A recent paper published in Molecular Biology and Evolution has drawn attention to something that many people will recognise on a deeper level, even if they have never come across the science before. The study looks at human-specific changes in the brain, particularly within the neocortex, and identifies a group of neurons that appear to have evolved unusually quickly compared to other species. Alongside this rapid development, the researchers found that a large number of genes linked to autism are also active within these same pathways, suggesting that the biological systems which supported the expansion of human intelligence are closely tied to those involved in neurodevelopmental variation.

What is being described is not a single gene or a simple cause, but a shift in how groups of genes are expressed during brain development. In evolutionary terms, this kind of change would have been highly advantageous. Increased cognitive capacity, enhanced pattern recognition, more complex language, and the ability to think abstractly would all have supported survival, social organisation, and the development of human culture. These are not small changes! They represent a significant leap in how the brain processes and integrates information.

However, what the research also suggests is that this increase in complexity comes with a cost. When systems become more intricate, they also become more sensitive to disruption. The same genetic pathways that support higher-order thinking appear to operate closer to a threshold, meaning that smaller variations in development, environment, or biological support can have a much greater impact on how those systems function. This is where we begin to see the overlap with autism and other neurodevelopmental patterns.

When you bring this into the detail of specific pathways, it becomes much clearer why this variability exists. Dopamine-related genes, such as COMT and DRD2, would have supported increased focus, motivation, and the ability to detect patterns and make connections, all of which are essential for complex thinking and problem solving. In some individuals, these traits remain highly advantageous, supporting deep concentration, creativity, and sustained engagement. In others, particularly where the system is under pressure, the same pathways can contribute to cognitive overload, difficulty disengaging, or fluctuations in attention and reward processing.

Serotonin-related genes, including SLC6A4, influence how the brain filters and processes emotional and sensory information. From an evolutionary perspective, increased sensitivity to the environment would have been beneficial, allowing for heightened awareness of social cues, danger, and changes in surroundings. However, when this sensitivity becomes too high, or when regulatory systems are not strong enough to manage it, it can lead to overwhelm, anxiety, or difficulty integrating sensory input.

GABA and glutamate pathways add another layer to this. The balance between excitation and inhibition is fundamental to how the brain regulates itself. Efficient GABA function allows the system to settle, filter, and prioritise information, while glutamate drives activity and signalling. Genes involved in this balance, such as GAD1, would have been critical in managing the increased neural activity that comes with a more complex brain. When this balance is disrupted, the system can become overactive and less able to regulate, leading to heightened reactivity, sleep disruption, and sensory sensitivity.

Methylation sits underneath all of these systems, influencing how effectively they function. Genes such as MTHFR, MTR, and MTRR are involved in processes that regulate neurotransmitter production, detoxification, and gene expression itself. In evolutionary terms, efficient methylation would have supported the increased demands of a more complex brain, ensuring that neurotransmitters are produced and cleared effectively and that the system remains stable under varying conditions. When methylation is less efficient, the entire system becomes more vulnerable, as the processes that maintain balance are not able to keep up with demand.

This is where the variation between individuals becomes particularly important. The same genetic changes that were advantageous at a population level do not express in the same way in every individual. In some people, the system is well-supported, both genetically and environmentally, and these traits manifest as strengths, such as intelligence, creativity, or heightened perception. In others, where there are additional pressures such as nutrient deficiencies, chronic stress, inflammation, or environmental load, the same underlying sensitivity can shift into dysregulation.

This is not about genes being good or bad. It is about how they are expressed within the context of the whole system. A highly sensitive, high-capacity system requires more support, more regulation, and more stability in order to function well. When that support is not in place, the system can move more quickly towards overwhelm.

This is something I have been working with for a long time. When I look at genetic reports, I am not looking for a diagnosis, I am looking for patterns across these pathways. Dopamine, serotonin, GABA, methylation, detoxification, and how they interact. I am looking at where the system is likely to be sensitive, where it may become overloaded, and what can be done to support it more effectively. When this is combined with an understanding of the nervous system and the individual’s lived experience, the picture becomes far clearer than any diagnostic label alone.

What this research offers is a framework that helps explain why these patterns exist. It supports the idea that neurodevelopmental differences are not separate from human development, but part of the same evolutionary trajectory. Increased complexity has brought increased capacity, but also increased variability and sensitivity. From a clinical perspective, this reinforces the importance of working with the system as a whole, supporting the underlying biology rather than focusing solely on the outward presentation.

For those of us who have been observing this in practice for many years, it is not a new concept, but it is a welcome shift to see it reflected in the research. It brings a level of coherence to what can often feel fragmented, and it opens the door to approaches that are better aligned with how the system actually functions.

Neurodiversity is a necessary and crucial piece of the puzzle of our evolution!