I have often thought that perhaps the rise in mental disorders in children such as autism could be related to people waiting until later in life to have children, at which point, their DNA has already begun to break down. Studies showing that the oldest child in a family tends to also have a higher IQ is consistent with this. The younger you are when you reproduce, the more fit your genes are, and therefore the smarter, healthier, etc. your children are likely to be. Economic pressures now make people wait until later to reproduce than they did a generation or two ago, but this could be counteracted by saving genetic material in a lab when one is young, then later, when one is economically ready to reproduce, one can make use of the stored material to do so. It is unlikely in the near future that people will all of a sudden want to go back to having kids right out of high school, so, for optimum gene selection, they should at least save off their genetic material (sperm, eggs) for future use. Otherwise, going forward, the average intelligence of the populace is likely to decline.