“So what are you getting at?”
“Yellowstone is no Tambora, Abel. Or, let me put another way. Mount St. Helens was the biggest volcanic eruption in recent times in this country. People think that it was some absolutely monstrous, remarkable event. It was really a little popgun. When held up against Tambora, Mount St. Helens was a kitchen match compared to a gasoline tanker truck explosion.”
“And Yellowstone?”
“Same thing. Only Yellowstone could be the Hiroshima A-bomb compared to Tambora’s gas truck. We don’t know just what Yellowstone is all about yet, but I can tell you, Abel, if Yellowstone’s caldera blew out, it would be capable of changing global climate drastically, probably for years.”
“How do you know all this, Bobcat?”
“My hobby.”
“Your hobby?”
“I’ve been interested in prehistoric life as long as I can remember. You know, you’ve seen my library. I’m addicted to the history of the evolution of life on this planet.”
“Our one ordained minister has a passion for evolution theory?”
“That’s me, Abel—creationism and evolution in one very unkempt package.”
Both men shared a laugh.
“So what does Yellowstone have to do with evolution?”
Bobcat leaned back in his chair and scratched his naked head. “Do you know anything about the great dyings?”
“Extinctions?”
“Yes, mass extinction events. Throughout the history of life on earth there have been scores of extinction events, large and small. But there have been at least half a dozen catastrophic extinctions, where much of the life on earth went extinct in the geological wink of an eye.”
“You mean like the dinosaur extinctions?”
“Yes, like the dinosaurs. But there were others, like the P-T, the Permian-Triassic boundary extinction event. Now that was huge. As many as ninety percent of all living things vanished. Imagine that. Ninety percent.”
“What does mass extinction have to do with Yellowstone, Bobcat?”
“Look, my man, unusual geological events have happened hundreds of times over geologic time. Volcanoes can trigger great change. Scientists now think that caldera upheavals, in particular, have had a profound effect on the history of life.”
“If that’s the case,” said Abel cautiously, “where does Yellowstone fit into all of this?”
Bobcat puffed up his mouth and released a steady stream of air. He sat silently for long seconds then cast his eyes on Abel.
“Let me explain something. Volcanoes are one way the earth releases energy and builds landforms. Calderas over giant hot spots in the earth’s mantle are another. They have vaguely similar origins, but most volcanoes are tiny geological structures compared to a caldera the likes of Yellowstone. A super caldera is really a receptacle for an immense sea of magma pooled a few miles down below the earth’s surface. That’s the way it is at Yellowstone. I can’t quite remember, but I think the caldera at Yellowstone is something like 1,500 square miles in size. You could fit hundreds of Mount St. Helens inside it.”
Bobcat let that tidbit of information hang in the air. “Now, would you mind if I bring up another Mount St. Helens-Tambora analogy?”
“No, Bobcat, let’s have it.”
“Okay, let’s do some time travel, then. About 75,000 years ago, a super-volcano by the name of Toba erupted catastrophically. Humans were around at that time. There might very well have been several hundred thousand humans on the planet then. People just like us. No different. They didn’t have cars and toasters, but they were just like you and me.”
Abel chuckled at Bobcat’s cars and toasters remark.
“If Tambora was that gas truck explosion, then Toba was a tanker ship loaded with liquefied natural gas going off. Tambora is considered a seven on the eight-point volcano energy release scale—the maximum is an eight, see. The Toba explosion was a full order of magnitude greater than Tambora. Toba was an eight out of eight on the scale. By contrast, Mount St. Helens would have been a five on the chart; it was probably ten thousand times less powerful.”
“Okay. What about us? What happened to human beings?” Abel rubbed his eyes to ward off the lateness of the hour, then looked to Bobcat for the answer.
“It was hard times 75,000 years ago, and I do mean hard times. Following Toba’s blowout, global temperatures fell like a stone around the world for a decade. The human population crashed to maybe just a few thousand.”
Abel was skeptical. “How in the world could anyone figure that out? No one was around to take a census, Bobcat.”
“That’s not exactly right, Abel. We do have a census, in a way, in the form of mitochondrial DNA.
“What, a genetic fingerprint?”
“You’ve got it. That’s a good way to put it,” smiled Bobcat through his neatly-trimmed beard. “Toba left an unmistakable impression—fingerprint, if you will—on our mothers’ mitochondrial DNA. That DNA is maternal; it’s passed down only through the female of the species. The rate of change, the mutation rate, is known. Since the rate of change is understood, the human population today should exhibit a much greater range of mitochondrial DNA mutation than it exhibits when we study it. If we’ve been around as long as we have, our mitochondrial DNA should be showing its age. But it isn’t.”
“Okay, fill me in,” Abel insisted.
“Well, the genetic makeup of our mitochondria should show evidence of much greater genetic variation. It doesn’t. That means something. Genetic researchers published papers postulating that some time in the deep past, about 75,000 years ago, something happened to the human population to suppress it, to nearly kill us off as a species. They had no idea what the mechanism was that caused the human population to drop to near zero and the DNA mutation clock to be stopped in its tracks and reset.
“Geologists and vulcanologists had the murder weapon, of course, but they weren’t working with geneticists. A bit of serendipity entered the picture about a dozen years ago, when a geologist happened to attend a genetics lecture. The speaker raised the question about what may have been the mechanism that would have reset the genetic time clock. The scientist in the audience had just read a paper about the Toba catastrophe in Southeast Asia 75,000 years ago. Eureka! Case solved.”
Abel attempted to internalize what he had just heard. “So, you’re telling me that a huge volcano blew up half way around the world and humans that were living in Africa and Asia nearly went extinct because of the changes the explosion wrought. That’s what you’re saying?”
“That’s exactly what I’m saying,” affirmed Bobcat. “Those few lucky humans that survived in some remote pocket of the world now carried with them mitochondrial DNA that was very similar. It’s very uniform in us all today. The mutation evidence of the deep past had been erased to a great extent. Now the mitochondria had to accumulate all new mutation evidence, if you can call it that.”
“How did those few people survive?”
“If I had to guess, I would say they survived because they were in the best possible place to survive. They were, of course, living out in the wild. They weren’t living in cities or towns or on farms. They were roughing it. They were hunter-gathers. The ones who made it through holy hell were probably those who lived on or near the equator, and they lived on the seacoast.”
“Why the seacoast?”
“Food, plenty of food, all the time. And there were equable temperatures, or at least steadier and warmer temperatures due to warm seawater at the coastal margins. Terrible conditions elsewhere would have been moderated at the coasts and there would have always been food, even if it were only in the form of dead creatures and seaweed to scavenge, washing up ashore.”