Researchers have turned up a new clue to the workings of a possible environmental factor in autism spectrum disorders (ASDs): fathers were four times more likely than mothers to transmit tiny, spontaneous mutations to their children with the disorders. Moreover, the number of such transmitted genetic glitches increased with paternal age. The discovery may help to explain earlier evidence linking autism risk to older fathers. The results are among several from a trio of new studies, supported in part by the National Institutes of Health (NIH), finding that such sequence changes in parts of genes that code for proteins play a significant role in ASDs. One of the studies determined that having such glitches boosts a child’s risk of developing autism five to 20 fold.