Autism almost certainly existed long before anyone had a name for it. The genes most strongly linked to autism risk are not recent mutations; many trace back hundreds of millions of years to some of the earliest vertebrates. What changed over the last century was not the appearance of autism itself but the development of language, diagnostic frameworks, and cultural awareness to recognize it. That distinction matters, because the dramatic rise in autism diagnoses since the 1990s has fueled a persistent misconception that autism is a modern phenomenon, when the evidence points in the opposite direction.
Autism Risk Genes Are Older Than Mammals
One of the strongest arguments that autism has deep roots comes from genetics. Researchers studying the evolutionary origins of autism-associated genes have found that these genes are significantly older than the average gene in the human genome. Many of them radiated during the Cambrian period, when early vertebrates were undergoing whole genome duplication events that shaped the foundations of nervous system development. These genes are also tightly conserved across the animal kingdom, meaning evolution has kept them largely intact across species for a very long time, a sign they play critical roles in brain function that natural selection protects rather than discards.1PubMed. Ancient roots: A Cambrian explosion of autism susceptibility genes
A separate analysis confirmed that autism risk genes are more ancient compared to other genes in the genome and tend to be unusually long, with complex regulatory sequences that help control when and how they are expressed during development.2PubMed Central. Autism risk genes are evolutionarily ancient and maintain a unique feature landscape that echoes their function The fact that these genes have persisted across hundreds of millions of years of evolution suggests they are not harmful accidents. They appear to be deeply embedded in the biological machinery that builds brains.
This raises an obvious question: if these genes are so old and so well-conserved, why haven’t they been weeded out? One explanation is that many of the genes involved in autism susceptibility also contribute to traits that are advantageous, such as aspects of cognition and intelligence. Because autism involves many genes rather than just one, the same genetic variants that increase autism risk in certain combinations may, in other combinations, support cognitive abilities that improve reproductive success.3PubMed Central. Evolutionary approaches to autism- an overview and integration This is not a fringe idea in evolutionary biology. Traits that persist at stable rates across populations despite apparent costs almost always turn out to have some compensating benefit, either directly or through related genes.
Descriptions That Predate the Diagnosis
The word “autism” entered clinical vocabulary in the 1940s, but detailed descriptions of people who would likely meet today’s diagnostic criteria appeared much earlier. The clearest pre-Kanner account came from Grunya Efimovna Sukhareva, a Soviet child psychiatrist who published a paper in a German scientific journal in 1926, almost two decades before Leo Kanner’s landmark 1943 paper. Sukhareva described a group of children whose clinical presentation closely resembles autism according to current criteria.4PubMed. Revisiting the history of autism before Kanner and Asperger: a tribute to Grunya Sukhareva Her work was published in German and Russian but remained largely unknown in the English-speaking world for decades, a historical accident that delayed recognition of how long clinicians had been observing this pattern.
Going further back, historical literature contains accounts of individuals whose described behaviors are consistent with what we now understand as autism. Myths and legends across cultures include figures with traits that map onto the autism spectrum, though interpreting these retroactively requires caution. The history of ideas about autism stretches across myths, legends, accounts of specific individuals in historical literature, and the eventual search for identifiable clinical subgroups, long before the current view of a wide spectrum emerged.5Autism. The History of Ideas on Autism
The picture that emerges is not of a condition suddenly appearing in the twentieth century but of observers across centuries noticing unusual patterns of behavior and social interaction without having a unifying framework to connect them.
How Getting a Name Changed Everything
When Leo Kanner described “infantile autism” in 1943, and Hans Asperger published his own observations around the same time, they gave the medical world a category to organize something that had always existed but had never been consistently labeled. Still, it took decades for that label to become an official diagnostic category. Autism was not included in the Diagnostic and Statistical Manual of Mental Disorders until its third edition, DSM-III, published in 1980. That inclusion fundamentally changed both clinical practice and research, because having an official category meant that clinicians had shared criteria to apply and researchers had a defined population to study.6PubMed Central. The Diagnosis of Autism: From Kanner to DSM-III to DSM-5 and Beyond
Each subsequent revision of the DSM broadened the definition. DSM-IV in 1994 added Asperger’s disorder and pervasive developmental disorder not otherwise specified, capturing people who would have been excluded under the narrower 1980 criteria. DSM-5 in 2013 folded everything into the single umbrella of autism spectrum disorder. Each broadening pulled more people into the diagnosis who had always been autistic but did not previously meet the formal threshold. The category expanded, not the condition.
Why Diagnoses Have Risen So Sharply
The most common version of the “is autism new?” question is really about the numbers. Reported autism prevalence has climbed steeply over the past three decades. A systematic review of global prevalence data found that the measured increase reflects the combined effects of greater community awareness, improved case identification, evolving diagnostic definitions, and expanded public health capacity to screen and diagnose.7PubMed Central. Global prevalence of autism: A systematic review update In other words, we got better at finding something that was already there.
One concrete mechanism behind the rise is diagnostic substitution, where individuals who would previously have received a different diagnosis are reclassified as autistic under updated criteria. A study of California’s developmental services data estimated that roughly 26% of the increased autism caseload between 1992 and 2005 was attributable to diagnostic change through a single pathway: individuals who had previously been diagnosed only with intellectual disability later received an autism diagnosis instead.8PubMed Central. Diagnostic change and the increased prevalence of autism And that was just one pathway. Other forms of reclassification, along with increased screening in populations that were previously overlooked entirely, account for additional portions of the rise.
None of this proves that no part of the increase is “real” in the sense of more people actually being autistic today than in the past. Environmental factors, including parental age trends, prenatal exposures, and other influences are actively studied and likely play some role.9PubMed Central. Environmental factors influencing the risk of autism But the bulk of the documented rise is accounted for by changes in how we define, detect, and record autism rather than by a genuine surge in the underlying condition.
The Problem with Diagnosing the Dead
Lists of “famous people who were probably autistic” circulate widely, with names like Einstein, Newton, Mozart, and others appearing regularly. These retrospective diagnoses serve an understandable purpose: they normalize autism and suggest that autistic people have always made major contributions to society. But they sit on shaky ground scientifically.
The core challenge is that you cannot clinically assess someone who is not alive. A 2003 claim by autism researcher Simon Baron-Cohen that Einstein had Asperger’s syndrome drew sharp criticism from historians of science, who argued that reconstructing diagnoses from scant biographical evidence is unreliable and amounts to myth-making.10arXiv. Retrospectively Diagnosing Einstein with Asperger’s Syndrome and the Dismal Failure of Debunking Myths The philosophical objections go deeper than just “we can’t be sure.” Retrospective diagnosis faces an ontological problem (did the disease as currently defined even exist as the same entity in a different historical period?) and an epistemic problem (we cannot access the kind of direct observation that diagnosis requires).11PubMed Central. Retrospective diagnosis of a famous historical figure: ontological, epistemic, and ethical considerations
That said, these attempts do illuminate something genuine. The biographical accounts of many historical figures include patterns of behavior, intense narrow interests, social difficulties, and sensory sensitivities that are recognizable to anyone familiar with the autism spectrum. Even if we cannot confirm individual diagnoses, the sheer number of plausible candidates throughout history supports the broader claim that autistic people have always been part of human populations.
Culture Shapes How Autism Appears
If autism has always existed everywhere, you might expect its signs to look the same across cultures. They do not, at least not entirely, which has complicated both historical recognition and current global screening efforts.
In Western diagnostic frameworks, limited eye contact is a hallmark sign of social communication difficulty. But in Chinese culture, children are taught that making direct eye contact with adults is impolite, so the “lack of eye contact” criterion does not work the same way. Researchers have noted that in Chinese contexts, autism-related communication difficulties may show up as atypical eye contact rather than absent eye contact, a subtle but important distinction that Western-designed screening tools can miss.12PubMed Central. A conceptual framework for understanding the cultural and contextual factors on autism across the globe Similarly, in Ethiopia, highly ritualized social greetings are culturally important, and caregivers of autistic children sometimes report that their child greets people well, interpreting as a strength what might otherwise be flagged as rigid, repetitive behavior.
A cross-cultural comparison of autism screening items across India, Japan, and the United Kingdom found that while the strongest indicators for predicting an autism diagnosis largely overlapped across all three countries, several items showed meaningful cultural variation. At least four items were highly effective at identifying autism in one or two cultures but performed poorly in the third.13PubMed Central. A cross-cultural study of autistic traits across India, Japan and the UK The core features of autism appear to be universal, but the surface expression is filtered through cultural norms in ways that have historically made it harder to recognize in non-Western settings.
This cultural filtering almost certainly contributed to autism being “invisible” in many societies for much of history. If the dominant culture interprets a trait as shyness, rudeness, spiritual difference, or intellectual disability rather than as a manifestation of a neurodevelopmental condition, the condition does not get recognized as a distinct pattern, even though the individuals are right there.
Why Women Were Overlooked for Decades
Gender is another lens through which autism was historically hidden in plain sight. Kanner’s original case series, and much of the early research that followed, skewed heavily male. For decades the assumption was that autism was simply far more common in boys, with ratios of four-to-one or higher commonly cited. The reality is more complicated.
Research into the “leaky pipeline” between community diagnosis and research participation has found that using standardized diagnostic instruments like the ADOS as a confirmatory measure resulted in the exclusion of autistic females at a rate over 2.5 times higher than that of autistic males. When studies relied on community diagnosis rather than these confirmatory assessments, the sex ratios were significantly more equal.14PubMed Central. Exclusion of females in autism research: Empirical evidence for a “leaky” recruitment-to-research pipeline In other words, the tools designed to confirm autism were themselves biased against recognizing it in girls and women, who tend to present differently and are more likely to develop compensatory social strategies that mask their underlying traits.
This means that for much of the twentieth century, a substantial fraction of autistic people, disproportionately female, were living undiagnosed. They existed; they were autistic; they simply were not counted. Accounting for this historical undercount further supports the view that autism has always been more common than the numbers suggested at any given time.
Autism-Like Behavior in Other Species
If the genetic underpinnings of autism are truly hundreds of millions of years old, you might expect to see analogous behavioral patterns in other animals. This is exactly what researchers have explored. For over a decade, genetically modified rodent models have been used to study the molecular and circuit-level mechanisms underlying autism-related behaviors. More recently, gene editing tools have been used to create non-human primate models that display autism-associated behavioral changes, including altered social interaction patterns and repetitive behaviors.15PubMed Central. Modeling autism in non-human primates: Opportunities and challenges
These animal models are not “autistic” in the human clinical sense. Animals do not have language, complex social norms, or inner lives that map neatly onto human diagnostic criteria. But the fact that manipulating the same ancient genes produces recognizable shifts in social behavior and behavioral flexibility across species supports the idea that the biological substrate for autism is deeply woven into vertebrate neurology, not a quirk of modern human life.
The Neurodiversity Reframing
The question “has autism always existed?” carries an implicit second question: “what is autism, exactly?” For most of the twentieth century, the dominant framework treated autism as a disease or disorder, something that went wrong in brain development. Over the past two decades, the neurodiversity movement has offered an alternative framing, viewing autism as one form of natural variation within a diversity of minds rather than a pathology to be corrected.16PubMed Central. Annual Research Review: Shifting from ‘normal science’ to neurodiversity in autism science
What makes this framing relevant to the historical question is that it aligns with the evolutionary evidence. Both evolutionary psychiatry and the neurodiversity movement reframe conditions like autism as natural cognitive differences rather than disease, expand the concept of “normal” beyond what conventional psychiatry has typically implied, focus on relative strengths, and recognize that modern environments may disadvantage certain individuals in ways that create functional impairment.17PubMed. Changing perspectives on autism: Overlapping contributions of evolutionary psychiatry and the neurodiversity movement Under this view, autism is not something that “happened” to humanity at some point. It is a persistent pattern of neurological variation that has been part of the human species for as long as there have been human brains, and arguably longer.
Paternal Age and Modern Risk Factors
Even if autism has ancient genetic roots, modern environmental and demographic factors can shift how often it occurs at the population level. One well-studied factor is paternal age. As men age, their sperm accumulates new spontaneous mutations, and some of these can affect neurodevelopmental genes. A large study found that offspring of a 45-year-old father had roughly a 10% increase in autism risk compared to offspring of a 25-year-old father.18PubMed Central. Paternal-age-related de novo mutations and risk for five disorders
However, the same study found that the observed population-level effect of paternal age on autism risk was nearly an order of magnitude larger than what could be explained by new mutations alone. The epidemiological risk associated with advanced paternal age was about 9.3 times greater than the risk attributable to spontaneous genetic changes, suggesting that other factors correlated with older fatherhood, such as socioeconomic patterns, access to diagnostic services, or heritable traits in men who have children later, account for most of the association.
In a world where the average age of fatherhood has been rising in many countries, this could contribute modestly to a genuine increase in autism incidence alongside the much larger effects of diagnostic expansion and awareness. But even a genuine increase in incidence does not mean autism is new. It means the dial moved slightly on something that was already present. Given that the relevant genes predate the existence of mammals, the condition itself is not going anywhere, nor did it recently arrive.