Pope’s travel tales are second to none, and his journeys have helped him piece together the story of life itself over immense pieces of geologic time.
Pope is a geology professor at Washington State University, and he studies fossil evidence of the most dramatic set of changes in life on our planet. Most of Earth’s long history happened long before any animals lived on land. In fact, 90 percent of the total span of Earth’s enormous history was in this period, with only simple life forms like bacteria and worms, all living in the seas.
I’d like to be able to tell you how scientists explain that life remained so simple for so long, then rocketed into complexity in the last 10 percent of the story. But I can’t, because we don’t know why history transpired that way. But the basic facts themselves are clear from the fossil record, with important details in the story still being added by new discoveries in remote locations like those that Pope has explored.
It took us geologists a heck of a long time to see there were fossils in the rocks deposited in the long but ancient part of Earth history. For many generations, we literally stepped over the little markings that the worms left behind.
To give you a sense of what the ancient impressions from the first 90 percent of Earth history are like, let me mention that I can see the marks when I have my bifocals on my nose, but not otherwise. Still, once we learned to recognize what was there, geologists rather easily started finding the fossils from Earth’s oldest rocks all over the planet. That’s just an example of the basic fact that humans see best when they know what they’re looking for.
Pope has studied the great shift of animal life on Earth as the little worms that left the faint impressions were replaced with abundant animals that had shells, teeth and bones. From that point onwards, fossils are objects I can see without my bifocals, things obvious enough it’s child’s play to recognize them.
Once the big and obvious fossils appear in the rocks, the plot in the story of life accelerates enormously. Giant amphibians are soon followed by reptiles, then dinosaurs, birds and our own group, the mammals. That’s the part of life’s history that school children delight in, from enormous flying reptiles to woolly mammoths.
Pope reminded me recently that, long ago, when reptiles were the new kid on the block on Earth, an interesting series of changes led to severe climate change. There was a lot of carbon dioxide in the air back in the day, much more than anything we will see in our atmosphere in the centuries to come.
Pope has been studying rocks created during this time of fluctuating carbon dioxide. The evidence shows that glaciers advanced and retreated in many dramatic pulses as carbon dioxide levels dropped from their earlier, high levels. The changes were the opposite of steady, with shifts back and forth as common as dirt. That’s a pretty good parallel to what we’ll see in the coming centuries and millennia, Pope thinks, except that we are now headed in the opposite direction due to burning fossil fuels.
The Earth plainly teaches us that the only true prediction about climate is the forecast of constant change and dramatic reversals. There’s no comfort in that lesson, but people like Pope have gone to the ends of the globe to establish what we can know of the future by looking at Earth’s past.
Dr. E. Kirsten Peters is a native of the rural Northwest, but was trained as a geologist at Princeton and Harvard. Questions about science or energy for future Rock Docs can be sent to firstname.lastname@example.org. This column is a service of the College of Sciences at Washington State University.