This could be as simple as the eggs and sperm getting older. Women used to have a first kid around age of 18, now it is closer to 30, and often late thirties. Same goes to the man. These first kids recently are produced from twice older sperm and eggs. Without going deep into genetic degeneration, let's say, that the eggs are not that fresh anymore.etrified:
This is a misconception. People are not getting married or having children later today. At least not in northern Europe. There are big cultural differences between countries, so that in parts of Africa or in India it may be or may have been common to marry and have children very young (even as young as 12). Non-Western countries are increasingly adopting Western practices though.
However, the median age of marriage in Europe in the 16th century was already around 26 years old (27 for men and 25 for women). I clearly remember seeing a chart with the evolution of the median age of marriage in England since the 16th century, and how it lowered to 23-23 years old in the early 19th century, then went up again to 26-27 years old in the late 19th century, then down again in the mid 20th century (probably as a result of WWI and WWII), to rise again in the late 20th century. Unfortunately I cannot find it anymore (it might have been in a book I read and not on the Internet). All I could find was the median age of marriage in the USA from 1890 to 2010. This page on the social history of Europe, though, confirms my recollections. Europeans married in their mid-20's in the Middle Ages, and late 20's or later from the 16th to 18th century. There are small fluctuations over the decades and centuries, but nothing tremendous.
Therefore I do not believe that autism is more common today because people are having children at an older age. I also do not believe that autism is more common today. The annual increase that is reported by doctors is simply the result of better screening and more parents sending their kids to the shrink when they don't fit nicely in the system (especially in the USA).