Probably the only reason this didn't happen sooner is because it couldn't: It was only episode #1.

Via Raw Story (whose use of the phrase "appeared to be an editing error" after this incident happened on a FOX affiliate in Oklahoma shows a touching, almost child-like faith):

In what appeared to be an editing error, a Fox affiliate in Oklahoma managed to remove the only mention of evolution from Sunday night’s Cosmos science documentary by cutting only 15 seconds from the broadcast.

The much-anticipated reboot of Carl Sagan’s legendary Cosmos premiered on Sunday with an overview of the history of the Universe, from the Big Bang to the advent of humans.

It wasn’t until the last 10 minutes of the show that host Neil deGrasse Tyson hinted at human evolution. “We are newcomers to the Cosmos,” he explained. “Our own story only begins on the last night of the cosmic year.”

“Three and a half million years ago, our ancestors — your and mine left these traces,” Tyson said, pointing to footprints. “We stood up and parted ways from them. Once we were standing on two feet, our eyes were no longer fixated on the ground. Now, we were free to look up and wonder.”

But for viewers of KOKH-TV in Oklahoma City, that 15 second paragraph was replaced by an awkwardly-inserted commercial for the evening news. The edit was caught on video and uploaded to YouTube by Adam Bates.

Before/after videos available at the link.

When I heard that the "Cosmos" reboot was going to be on FOX, I wondered how on earth it could work without a hitch. Asked and answered, I suppose.