My new contribution to the series “The Moral Is” (hear my previous essays in their archives, or read them here) on Valley Public Radio was broadcast during Valley Edition a couple of weeks ago. Here’s my original, extended version of the essay, before it was pared down for broadcast. You can imagine me reading it in your head, or listen to the broadcast version recorded in my voice.
Sixty-five million years ago, an asteroid crashed into the earth near modern day Yucatan, setting off a chain of geological and climatic reactions that wiped out the dinosaurs. Nearly 70% of all species alive on that day disappeared forever.
This was the last known mass extinction event in Earth’s history. It was the fifth time that such a mass extinction has occurred on our planet. As far as we know.
The history of these extinctions is quite literally written in stone, in the fossils trapped in layers of rock. Like the pages of an ancient and incomplete book, these layers are inscribed with the story of the plants and animals and bacteria that have lived and died here since long before us.
The tools of paleontology help us decipher these stories written in stone. We can read of the long age of bacteria and other single-celled organisms; of the time when the air held no oxygen because no one had figured out how to make food from sunlight; of the first time that living organisms changed the global climate by releasing oxygen, likely triggering the first mass extinction of species who couldn’t breathe the air that sustains us now.
A later chapter tells of the age of carbon, when dense forests covered the land, before getting buried deep under it to be transformed into coal and oil. Now we burn the solar energy captured in carbon by those ancient forests to enrich our short lives. In doing so, we have transformed the earth’s climate yet again, dangerously.
The first stirrings of plants and animals on to land make for thrilling reading. We particularly love the tale of the plucky fish caught in tidal pools which began breathing the air and crawling around on land! How they eventually gave rise to the land mammals we call our own kin.
We discover pieces of our own story everyday, from humble origins as apes that stood up in Africa and spread out of that continent probably to escape a changing climate, and eventually occupied the entire planet.
Five times during the past billion years, this riveting story is interrupted by unspeakable horrors as some terrifying series of unfortunate events conspired to wipe out most species. Each time, the survivors got a fresh start to evolve on a mostly empty planet.
The Great Dying at the end of the Permian era 250 million years ago was the worst one yet, driving more than 90% of species extinct, including many among the otherwise hardy insects. But it cleared the way for reptiles and mammals. We don’t quite know what caused the Permian mass extinction, but massive, perhaps sudden climate change may have a played a big role.
The asteroid that took out the big dinosaurs at the end of the Cretaceous was a mere lump of rock drifting in orbit around the sun until it fell to Earth and wiped life’s slate almost clean for the fifth time. Driven by sheer gravity, that asteroid had no conscience or remorse about the horrors it would unleash. Nor any notion that humanity would eventually evolve in the absence of dinosaurs to become another force of mass extinction.
Now we find ourselves on yet another brink, where our own industrial civilization threatens a Sixth Great Dying. Within the past century, we have increased the pace of extinction, willfully or unwittingly, to a level last seen only in the wake of that asteroid. We have come so far, in building our diverse cultures and technologies, achieved so much worth celebrating given our humble origins. Yet our biggest legacy may end up as the epitaph for the sixth mass extinction on Earth, which will doom us just as surely.
We like to think of ourselves as creatures of conscience, infused with a morality and an intellect that allows us to understand and appreciate our kinship with other creatures. But as drivers of this sixth extinction, how different are we from that asteroid? Will our conscience give us pause and pull us back from the horrors we have unleashed? Or will we let our own chapter end abruptly, wiping the slate clean again, just like that remorseless asteroid?