Summary
Neurodivergent traits — including those associated with autism and ADHD — are not modern anomalies. Emerging genomic evidence shows that the genetic variants underlying these traits have deep evolutionary roots, stretching back to archaic human populations including Neanderthals. This does not mean autism or ADHD are “caused by” Neanderthal DNA in a simple sense. It means the neural architectures that produce neurodivergent cognition are part of the long evolutionary history of the human brain, shaped by hundreds of thousands of years of selection, introgression, and genetic drift.
This page collects what is currently known about the evolutionary dimension of neurodivergence. It is a new area for this wiki, expanding beyond the wiki’s original focus on sensory processing to place that knowledge within a deeper biological context.
What the evidence shows
Neanderthal DNA contributes to autistic neurobiology
Pauly et al. 2024 — Neanderthal polymorphisms enriched in autistic probands analysed the SPARK cohort and found that rare Neanderthal-derived single nucleotide polymorphisms (SNPs) are significantly enriched in autistic probands compared to race-matched controls. Twenty-five specific SNPs were identified, some with clinical associations to intellectual disability, epilepsy, and language regression.
The enrichment is not random. Prior work has shown that Neanderthal DNA enrichment is associated with enhanced connectivity within visual processing systems and decreased connectivity within the default mode (social) network — a neural signature that closely resembles the connectivity patterns observed in autistic brains. The chain runs: archaic introgression → altered neural development → altered connectivity → the sensory and social phenotype we recognise as autism.
Neanderthal DNA shapes brain morphology
Gunz et al. 2019 — Neanderthal introgression and brain shape showed that modern humans with more Neanderthal-derived DNA in specific genomic regions have measurably less globular (more elongated) brain-case shapes. The variants involved are near genes for neurogenesis (UBR4) and myelination (PHLPP1) — these are developmental, not cosmetic, effects. The uniquely globular brain shape of modern humans, which evolved after the split from Neanderthals, may itself be a precondition for the specific cognitive profile that characterises modern human typicality. Deviations from that template — carried by archaic DNA — may contribute to the neural architectures underlying neurodivergence.
ADHD-associated alleles have an ancient trajectory
Esteller-Cucala et al. 2020 — ADHD evolutionary genomics traced ADHD-associated allele frequencies from Neanderthals through Palaeolithic, Mesolithic, and Neolithic human populations to the present. The alleles have been steadily declining — they were more common in ancient populations than they are today. Neanderthal-introgressed alleles are enriched in ADHD risk variants. The finding supports the mismatch theory (traits adaptive in one environment become costly in another) but pushes the relevant timescale back far earlier than the agricultural revolution.
The mismatch theory
The mismatch theory proposes that traits which were adaptive in ancestral environments become maladaptive when those environments change. For ADHD, the standard narrative has been: traits like impulsivity, novelty-seeking, and distractibility were useful for Palaeolithic hunter-gatherers but became problematic once humans settled into agricultural (Neolithic) life with its demands for patience, routine, and deferred reward.
The Esteller-Cucala evidence complicates this by showing the selective pressure is much older than the Neolithic transition. If ADHD-associated alleles were already declining in Palaeolithic populations, then the environmental mismatch is not simply “hunter-gatherer versus farmer.” It may reflect something more fundamental about the trajectory of human social complexity.
For autism, the mismatch theory is less developed but the Pauly et al. findings are suggestive. If Neanderthal-derived variants that affect visual-processing connectivity and reduce default-mode-network connectivity are enriched in autistic people, then the autistic cognitive profile — strong on sensory detail, different on social processing — may reflect a neural architecture that was more common in archaic populations. The modern environment, with its social density and sensory overload, may be the mismatch.
Why this matters
It deepens the “difference, not deficit” position
The position that sensory processing differences are differences rather than deficits gets stronger with evolutionary evidence: these traits are not errors in the genetic code. They are part of the deep structure of human cognitive variation, carried forward through 50,000+ years of introgression and surviving despite ongoing selective pressure. A trait that persists at these timescales is not a bug.
It connects sensory processing to larger biology
The Neanderthal connectivity findings (enhanced visual processing, reduced DMN connectivity) map directly onto the sensory-processing patterns documented in practice. The person who sees more detail, hears more nuance, and finds social inference harder is not just experiencing the world differently for psychological reasons — they may be running a neural architecture with ancient roots. This does not change the practical recommendations (build individual profiles, maintain prikkelbalans) but it changes the story behind those recommendations.
It connects autism and ADHD through shared deep history
ADHD co-occurs with autism at high rates (see the “Social/behavioral” class in Litman, Sauerwald et al. 2025 — Genetic programs underlying autism phenotypic heterogeneity). Understanding the evolutionary trajectory of ADHD-associated variants situates both conditions within the same deep history of human cognitive variation. The overlap problem (see The overlap problem) looks different when you see the shared genetic architecture not as diagnostic confusion but as a reflection of how human neurodevelopmental variation has been shaped over tens of thousands of years.
Open questions
- Does the mismatch theory apply to sensory processing specifically? The ADHD evidence is about behavioural traits (impulsivity, attention). Whether sensory processing differences — hypo- and hyperresponsivity — were ever adaptive in their own right is unstudied. One could speculate: heightened sensory detail processing might be advantageous for tracking, foraging, or predator detection. But this is speculation, not evidence.
- How does this interact with the genetic heterogeneity picture? The Litman/Sauerwald four-class model identifies distinct genetic programs. Do the Neanderthal-derived variants cluster in one class or cut across all four? Nobody has yet overlaid the two analyses.
- What about non-European populations? Most archaic introgression research focuses on Eurasian-derived populations because that is where Neanderthal DNA is most prevalent. African populations have less Neanderthal DNA but are not free of archaic introgression (Denisovan and other archaic human contributions exist). The evolutionary picture of neurodivergence in non-European populations is essentially unstudied.
Key sources
- Pauly et al. 2024 — Neanderthal polymorphisms enriched in autistic probands
- Gunz et al. 2019 — Neanderthal introgression and brain shape
- Esteller-Cucala et al. 2020 — ADHD evolutionary genomics
- Sherwood, C.C., & Bradley, B.J. (2018). “Brain Evolution: Mapping the Inner Neandertal.” Current Biology, 28(24), R1441–R1443. (Commentary on Gunz et al.)