Daniel Dvorkin's Journal: Because everyone knows Idiocracy was a documentary.

Show. Me. The. Data.

Dumb and Dumber: Study Says Humans Are Slowly Losing Their Smarts

The actual Trends in Genetics articles (paywalled, unfortunately; I urge anyone with access to read them) make it clear that this is not a "study" in any meaningful sense in the word, but rather a bit of unfounded speculation. Now, speculation is an important early step in the process of science, to be sure--but that speculation should be founded on observation, and the author offers none.

Unfortunately, this particular bit of speculation is (as I strongly suspect he knew it would be) a crowd-pleaser, playing as it does into the lost-golden-age mythology which has such universal appeal across all ages and cultures. (I speculate that it's something hardwired into the human brain, but I freely admit that I have no data to support this hypothesis, other than the observation that such a mythology exists.) An actual study would be a worthy project. This kind of sensationalism is just sad.

Original articles:
http://www.sciencedirect.com/science/article/pii/S0168952512001588
http://www.sciencedirect.com/science/article/pii/S016895251200159X

A very insightful critique:
http://www.sciencedirect.com/science/article/pii/S0168952512001941

Author's response to critique, which consists largely of saying "Nuh-uh!":
http://www.sciencedirect.com/science/article/pii/S0168952512002090