Just in time for the holidays, PBS' "It's Okay To Be Smart" has rolled out a "12 Days of Evolution" web series, and it is truly an early treat.

"Day four" of the series is a particularly salient one because it talks about the observability of evolution -- that's a fancy way of saying "yes, scientists have seen evolution in action. It's a thing. Go look outside."

In the episode, entitled "Have We Ever Seen Evolution Happen?" biologist and host of "It's Okay to Be Smart" Joe Hanson explains how evolution is all around us -- and we're sure Darwin would be just tickled.

"Male crickets love to sing," Hanson said. "But on the Hawaiian Island of Kauaii, that singing comes with a price. Several years ago, a parasitic fly arrived on the island. Those flies listen for crickets' chirping wings, lay eggs inside them, and those crickets are devoured from within."

Sorry, Jiminy Cricket.

The flies killed many crickets on the island, but the few that survived did so because of their wings.

Hanson then explained how "silent wing shape was caused by a mutation on the cricket's X chromosome," and "in less than 20 generations," the crickets re-populated and filled the island with the sound of silence. (Not the Simon and Garfunkel song, obvs. That'd be pretty unnerving.)

"Not only did we see natural selection happen in action, we saw it in the blink of an eye," Hanson said.

When those pesky flies showed up on the island of Oahu, the crickets weren't chirping. "Surprisingly, they had developed a completely different mutation in the same gene. Nature arrived at the same destination by two completely different paths."

In conclusion:

At a time when many schools across the country are still teaching creationism, this video is so important. It supports the fact that evolution is not a bedtime story, not an "option" to be learned in class, but an observable reality -- and that's pretty f--king cool.

You can check out the full video here. Feel free to share it liberally.