Large-scale genetic analysis allows scientists to find abnormal DNA in congenital diseases such as autism. Better diagnosis is helping doctors to detect the signs of autism in babies as young as six months. The current evidence shows that new mutations, mostly in the sperm of fathers 35 and over, are associated with autism. Unfortunately, it’s not just one mutation or genetic marker but almost a different one in every family: “Gene studies begin to unravel autism puzzle” (2012)
Also, it seems to be a genetic weakness or predisposition: autism is almost unknown in Africa but Africans who move to England start to see it. It has been associated with a lack of Vitamin D, which perhaps protects against the brain anomalies that cause autism: “What if Vitamin D deficiency is a cause of autism?” (2009). That children in the developed world are spending more time indoors could contribute to the problem.