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Filmed on Wednesday September 6, 02017

David Grinspoon

Earth in Human Hands

For thinking about the future of life on Earth in planetary terms, no one can match the perspective of an astrobiologist.

David Grinspoon notes two major shifts in Earth’s biological regime: 1) 2.1 billion years ago, when cyanobacteria flipped the whole planet from anaerobic to oxygen-based life; 2) now, as humans assume domination of the Earth’s living systems. “We suddenly find ourselves running a planet,” he says, “without knowing how it should be done. We’re at the controls, but we’re not in control.” The cyanobacteria were unaware of their role. We are aware of ours. What should we do about that?

Grinspoon is professor of Astrophysical and Planetary Science at the University of Colorado and Senior Scientist at the Planetary Science Institute. His books include: Earth in Human Hands: Shaping Our Planet’s Future (02016); Lonely Planets (02004); and Venus Revealed (01998).

Cognitive planet

Thanks to the growing human domination of natural systems on Earth, people say we are entering an Anthropocene Epoch, Grinspoon began, but what if the term “epoch” understates the consequence of what is going on? Astrobiologists recently learned that planet formation is the norm in the universe, and now they’re trying to find out if life formation is also the norm. They won’t look for signs of mere geological epochs on other planets; they’re looking for eon-scale transitions like the three that Earth has gone through in its 4.8 billion years, all caused by life.

About 4 billion years ago the Archean Eon began with the origin of simple life. Then 2.5 billions years ago the Proterozoic Eon unleashed “the Great Oxygenation Event” caused by cyanobacteria adopting solar energy (photosynthesis). “That’s when life took over the planet,” said Grinspoon. Everything accelerated further 542 million years ago with the Cambrian Explosion of complex life of plants and animals—the Phanerozoic Eon. Which we’re still in. Or are we?

Alien astrobiologists could have noticed the Proterozoic transition by detecting the dramatic destabilization of Earth’s atmosphere. The Phanerozoic transition would have been apparent from forest fires glowing on Earth’s night side, indicating combustible plant material. What would outside observers make of our current night side, blazing with dazzling cities? Or of bits of Earth firing off purposefully to orbit other planets and moons in the Solar System?

“Potentially,” Grinspoon suggested,”we’re at another eon boundary now, with an equally profound transition in the relationship between life and the planet, when cognitive processes become planetary processes. Is intelligence a planetary property, like life? Can it become a self-sustaining property, like life? Is civilization adaptive, or will it be a dead end?”

We can ask, what do humans have that similarly cataclysmic cyanobacteria did not have? Awareness, intention, collaboration, and maybe a sense of responsibility. “The Anthropocene dilemma,” Grinspoon said, “is that we have global influence without global control. So far we’re acting like adolescent planet vandals.”

He concluded, “In order to choose a constructive role rather than a destructive role, we have to see ourselves in the very long time scale. Our deep history shows that humanity is unique in its capacity for self-reinvention. If we can develop a mature, long-term, healthy relationship with world-changing technology and if we proceed with a careful combination of innovation and restraint, our planet could become Terra Sapiens—Wise Earth.”

(Bonus point: When asked why people seem to be more worried about engineers hacking genetic code than hacking digital code, Grinspoon said, “Maybe it’s because the monsters we can imagine are scarier than the monsters we can’t imagine.” He added, “We tend to learn things through exploration, not through imagination.”)

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