Increases in diagnoses have been increasing for decades, with one in 36 children in the UK believed to have Autism Spectrum Disorder. Globally, the World Health Organisation (WHO) estimates that around one in 100 children have autism. This rapid evolution involved a marked downregulation in genes linked with autism and schizophrenia, supporting the hypothesis that lower expression of autism-linked genes in humans increases the risk of autism. Whilst the exact cause of autism remains unclear, US researchers believe that its prevalence may be linked to human brain evolution (stock image)Your browser does not support iframes. However, they added that the reason as to why this change benefited humans remains unclear.