Autism spectrum disorder (ASD) may be the result of millions of years of evolution. Rapid neuronal evolution in humans is likely ASD\u2019s genetic cause. Though autism can cause certain developmental difficulties, the evolution of genes may have contributed to humans\u2019 complex minds today.<\/p>\n
Your brain on genes<\/p>\n Autism\u2019s \u201cexceptionally high prevalence\u201d in humans may be a \u201cdirect result of natural selection,\u201d said a study published in the journal Molecular Biology and Evolution<\/a>. The development of ASD in humans is likely a result of the \u201cpeculiar bargains evolution struck to make us human,\u201d said ZME Science<\/a>.<\/p>\n <\/p>\n The study found that the \u201cmost abundant type of outer-layer brain neurons, called L2\/3 IT neurons, evolved exceptionally quickly in the human lineage compared to other apes,\u201d said a news release<\/a> about the study. This \u201ccoincided with major alterations in genes linked to autism \u2014 likely shaped by natural selection factors unique to the human species.\u201d These genomic elements remained \u201crelatively stable throughout the rest of mammalian history,\u201d said Newsweek<\/a>.<\/p>\n The Week<\/p>\n Escape your echo chamber. Get the facts behind the news, plus analysis from multiple perspectives.<\/p>\n <\/p>\n \nSUBSCRIBE & SAVE\n<\/p>\n <\/a><\/p>\n Sign up for The Week’s Free Newsletters<\/p>\n From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.<\/p>\n From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.<\/p>\n Scientists also agree that neurological conditions like autism<\/a> and schizophrenia are probably a uniquely human condition. It is \u201cvery rare to find behaviors associated with the disorders in non-human primates,\u201d said Neuroscience News<\/a>. Also, \u201cbehaviors associated with those disorders generally involve cognitive traits like speech production and comprehension that are either unique to or much more sophisticated in humans.\u201d The evolution<\/a> of autism \u201cisn\u2019t about one rogue mutation,\u201d said ZME Science. Instead, it is \u201cabout dozens of small changes acting together, nudging the baseline wiring of human brains.\u201d It is likely that \u201cnatural selection actively favored these changes, even though they came with trade-offs.\u201d<\/p>\n Cause and effect<\/p>\n Approximately one in every 31 children is diagnosed with autism, according to the Centers for Disease Control and Prevention<\/a>. Scientists have known for a while that genetics is likely the largest contributing factor to being diagnosed with ASD. \u201cSeveral genes seem to be involved in autism spectrum disorder,\u201d said the Mayo Clinic<\/a>. Many of these genes are linked to developmental delays, which raises questions as to why evolution may take this path.<\/p>\n Although the definitive reason is unclear, researchers have ideas. For one, the \u201cevolution of autism-related genes slowed early brain development or expanded language capacity, extending the time window for learning and complex thought in childhood,\u201d said Newsweek. This \u201cextended development may have offered an evolutionary advantage by fostering more advanced reasoning skills.\u201d Essentially, \u201csome of the same genetic changes that make the human brain unique also made humans more neurodiverse,\u201d Alexander L. Starr, the paper\u2019s lead author, said in the release.<\/p>\n There have also been many theories about the factors that increase the risk of autism. Researchers have been looking into various environmental factors like \u201cinfections, medicines, complications during pregnancy or air pollutants,\u201d said the Mayo Clinic. Some have also claimed that vaccines<\/a> play a role in causing autism spectrum disorder, though \u201cmany well-done research studies show no link between autism spectrum disorder and any vaccines.\u201d<\/p>\n