Neurodiversity traits linked to Neanderthal admixture
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Description: Background. Among non-African populations, up to 6% of their genome has retained DNA from archaic hominins. While hybridizations were advantageous in adapting to out-of-Africa environments they have recently also been associated with disease risks (Simonti et al., 2016) and autism (Oksenberg et al., 2013). However, genome evolution operates primarily on gene networks, and alleles associated with increased risk may have undergone positive selection in the past and only become disadvantageous in modern life and culture. If autistic traits or, more generally, neurodiversity traits, are signatures of a Neanderthal or Denisovan admixture, the prevalence or strengths of those traits should vary with human migration and Neanderthal ancestry. We expect Europeans and East Asians are more closely related to each other than to Africans and to find strong autistic traits (at population level) in East Asians. Methods. We analysed over 500,000 responses from the Aspie Quiz which attracts people interested in how neurodiverse or neurotypical they are. The quiz yields two factors: a neurodiversity (ND) and a neurotypical (NT) score. Participants also indicated their ancestry. From the ancestry information we calculated a relatedness metric with hierarchical clustering. Results. Behavioural traits associated with neurodiversity (ND score) were most prevalent among participants indicating Eurasian ancestry and less prevalent among African and African-American participants. This data is less in favour for a single migration of modern humans out-of Africa. Discussion. Our results indicate a possible evolutionary explanation for autism. Autistic traits at the population level overlap with human admixture and migration, i.e. a closer relatedness among East Asian and Central Europeans than Africans. This finding uggests positive (or at least neutral) selection for genes / gene networks from Neanderthals. Indeed, autistic traits have been linked to Neanderthal alleles (Oksenberg et al., 2013). Our data is insufficient for disentangling cultural or other more recent influences on behavioural traits, nor can it measure the prevalence of neurodiversity. However, both recent evidence and our data suggests that autistic traits and neurodiversity come from Neanderthals.