Google "Flynn effect" to get the expert analysis on environment and IQ. The short version is that new generations grow up in an increasingly stimulating and enriched world, which boosts their overall IQ in comparison with the generations before them.
In my day, television was 7 channels of pablum. Now we have more than 7 channels of history and science alone.
In my day, if you had a question, you had to rely on the leaky memories of adults. For a more definitive answer, you could wait a few days to have access to a library, and take your time reading through a few sources. Today, you can instantly access thousands of sources, and cross-reference them for accuracy.
These are two major reasons why my DD will be way smarter than I am. I get to use this stuff now, but she gets to grow up in this world.
