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'Cosmos' recap: Wading into the tide pools of evolution

Sooner or later, if you’re making a TV show about science, you’re going to have to deal with the dreaded E-word.

More than 150 years after Charles Darwin published "On the Origin of Species," evolution remains a cornerstone of modern science as well as a lightning rod for controversy, particularly among the religiously devout. The pilot episode of "Cosmos: A Spacetime Odyssey," which aired last week, only briefly alluded to evolution (although even that was sufficient to spark rumors of censorship when a local Fox affiliate in Oklahoma cut into that segment to run a station promo, purportedly because of an “operator error”).

The opening for this week’s "Cosmos" episode ("Some of the Things That Molecules Do") wades right into those treacherous waters to explore the common ancestry of every living thing on Earth. Or rather, it dips its toe gingerly into those treacherous waters. You know, just to test things out a bit before plunging in.

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“This is the story about you and me and your dog,” our host, Neil deGrasse Tyson, purrs reassuringly from his perch by a cozy campfire in the woods. What could be less intellectually threatening than man’s best friend? The conceit is a little hokey, especially when Tyson makes a show of waving a flaming torch at encroaching wolves to hold them at bay.

But it provides a neat segue into the domestication of canines: dogs evolved from wolves that self-selected for “tameness” over many generations — Survival of the Friendliest. And eventually human beings began breeding only those dogs with the most desirable qualities: artificial selection instead of natural selection. “We took evolution into our own hands,” Tyson says.

Oh yes, he uses the “E” word, like it ain’t no thing — because it isn’t. The scientific evidence for evolutionary theory is overwhelming, after all, and Tyson is ready to show us just how this process works at the molecular level, via some nifty animations of DNA. We see twin strands being split and replicated as cells divide, a process that usually runs smoothly, although occasionally there are errors — tiny mutations, often inconsequential. But sometimes they can, say, alter the color of a bear’s fur, and you get a bear with white instead of brown fur. In an icy environment, that confers a survival advantage in the form of better camouflage; it’s easier for a bear with white fur to sneak up on prey. So nature selects for white fur and that mutation gets passed down through subsequent generations. And voila! You have polar bears.

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The episode deftly covers the basics of the Tree of Life, in which each twig represents a different species, with those most closely related on the same or nearby branches, and the trunk represents the common ancestry of all life on Earth. We grapple with the evolution of the eye, the marvelously complex result of random mutations over millions of years. No need to invoke an intelligent designer, Tyson assures us. Natural selection has got this covered too.

But evolution doesn’t easily adapt to sudden, catastrophic events, evidenced by the five mass extinctions that wiped out so many earlier species on Earth. Tyson focuses on the end of the Permian Era, when massive volcanic eruptions wiped out the trilobites.

I guess we’ll have to wait for a future episode to hear more about the crowd-pleasing dinosaurs, laid waste by that nasty asteroid. But we do get to marvel at the tiny-but-hardy tardigrade, or water bear — the only species to survive all five mass extinction events because they can thrive in the most extreme conditions. (It’s also why they’re such a popular choice for experiments in space.)

Finally, Tyson takes us to the rings of Saturn and its largest moon, Titan — one of the most promising bodies for discovering life elsewhere in our solar system. Sure, all the water on Titan is frozen because of incredibly low temperatures, but Titan does have a rich landscape of lakes and rivers of liquid methane. When it rains on Titan, it rains methane. Could there be life in Titan’s hydrocarbon lakes? That might depend on your definition of life: It would probably be quite different. You’d have creatures that inhale nitrogen instead of oxygen from the atmosphere, and exhale methane instead of carbon dioxide, and maybe use acetylene instead of sugar as an energy source. Perhaps one day we’ll send a mission to Titan to find out.

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The episode ends with another homage to the original "Cosmos": Carl Sagan’s classic animation running through 40 billion years of evolution in 40 seconds, from one-celled organisms to upright human beings capable of asking questions about the universe.

The connections between the segments in this episode felt a bit fuzzy and haphazard at times, but by the end, Tyson has laid out the facts of evolution simply and clearly and acknowledged the lingering opposition to such ideas in certain quarters, yet he never dwells too much on such “controversies” — and he never cedes the scientific ground. This is something else he shares with Carl Sagan, who managed to strike a delicate balance between recognizing people’s hunger for spirituality, and remaining faithful to the science.

Tyson is fond of saying that nature doesn’t care what you believe. And he’s right. That’s not really a bad thing. As Sagan wrote in one of my favorite books, "The Demon-Haunted World": "Plainly there is no way back. Like it or not, we are stuck with science. We had better make the best of it. When we finally come to terms with it and fully recognize its beauty and its power, we will find, in spiritual as well as in practical matters, that we have made a bargain strongly in our favor."

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