This confirms previous hints along the same lines in a 2013 study, a 2012 study, a 2010 study, and an earlier one in 2004 (discussed with the 2013 study).
Also, there is no doubt that there is a significant genetic component to autism spectrum disorders that is inherited from one's biological parents (see, e.g., here looking at sibling rates and this twin study). Stephen Hsu's take on this study includes excerpts from it that explains that there are many known specific genes that are risk factors for ASD.
But, oversimplified genetic models of the condition's prevalence fitted to the data also strongly suggest (particularly based on the link between prevalence and advanced parental age) that a very substantial share of all autism cases involve mutations that are novel to the child and not present in either parent's genome. My crude estimate in 2008 which nonetheless is still a pretty good fit to the data eight years later suggests that:
[A]bout a third of autism cases are due to non-age related mutations of in sperm or egg cells of parents who don't have an autism gene, about a third of autism cases are due to age regulated mutations in sperm cells of fathers aged 30 or more who don't have an autism gene, and about a third of autism cases are a result of inheriting an autism gene from a parent, usually a carrier mother or a mild ASD symptom parent of either sex.This estimate may be high, but is order of magnitude correct. For example, a 2014 study comparing whole genomes of individuals with ASD and their family members, found "de novo" mutations contributed to 30% of cases of male ASD and 45% of cases of female ASD (see also this 2015 study). Indeed, the cause of seriously developmental disabilities, in general, is roughly similar to the pattern observed in ASD spectrum disorders.
Also, one thing that we do know beyond any reasonable doubt is that vaccination does not cause autism.
A weak capacity for empathy is often considered a diagnostic symptom of autism. But, even if this is true, empathy can cause its own problems and can lead to bad moral decision-making by people in leadership positions. It isn't unreasonable to think that some level of neurodiversity is beneficial to our society, even if the most severe cases of autism are something no one should have to experience.