In July 2013, the Deep Time exhibits team went to North Dakota’s Hell Creek Formation to collect 66-million-year-old fossils. These fossils will be on display in our new exhibition on the Last American Dinosaurs while our permanent Fossil Hall is being developed. This is the 8th post in a series about our experiences out in the field.
On day three of the trip, our team stood on and even tasted the Cretaceous-Paleogene boundary—recorded in a thin line of sediment deposited about 66.1 million years ago, marking the extinction event that wiped out the dinosaurs. Here, under the blazing summer sun, Sant Director and paleobotanist Kirk Johnson answered the question, “What do our visitors need to know about how scientists understand the world?”
In just a few minutes, he described five major advances in scientific knowledge that have occurred since the Museum opened in 1910. These “five big leaps” have revolutionized the way humans understand our planet, its long history, and the forces that shape life. These leaps are one reason that the National Museum of Natural History is updating and expanding the National Fossil Hall.
- Plate Tectonics: Our understanding of the large-scale movement of the Earth’s outer layer (or lithosphere) expanded in the 1960s, when geologists combined older ideas about continental drift with newer findings about sea floor spreading and new crust formation along underwater mountain ranges. Taken together, the evidence indicated that the Earth’s surface is made up of numerous plates that move slowly, shifting over many millions of years. This motion generates earthquakes, creates mountain ranges, and leaves traces in the geological record that help scientists reconstruct Earth’s past landscapes.
- Evolution and Genetics: Over the past 60 years, we have increased our understanding of DNA’s role as the building block of all organic life. In 1953, James Watson and Frances Crick described DNA’s double-helix structure; 50 years later, scientists completed a 10-year, $3 billion collaborative effort to map the human genome. Recognizing DNA’s role in evolution has fundamentally changed the way we look at biology, paleontology, archeology, medicine—and ourselves.
- Deep Time: We’ve known for decades that the Earth is very old. But we couldn’t know exactly how old until fairly recently. In 1862, Lord Kelvin calculated the Earth’s age to be 20 million to 400 million years old, but by the 1920s scientists were putting the age in the billions. Now, thanks to our ability to use radiometric dating techniques, scientists calculate the Earth to be 4.567 BILLION years old (plus or minus 50 million years).
- Climate Change (Past and Present): Over the billions of years of Earth’s history, the planet has warmed and cooled in cycles characterized by changing atmospheric chemistry. We know this partly from studying the fossil record—a fossil’s chemical composition changes depending on what the atmosphere was like when the organism was alive. But since the beginning of the Industrial Revolution 150 years ago, when we began burning large quantities of fossil fuels, the rate of climate change has become more extreme. Currently, atmospheric carbon dioxide levels are the highest they’ve been in 15 million years – and since carbon directly affects climate, this is a big deal. Our growing global population (7 billion and counting) and our desire for energy are contributing to climate change on a scale that hasn’t been seen before in human history.
- Earth is Not an Island: It’s easy to forget the Earth is part of a vast universe with many, many factors over which we humans have absolutely no control. Advances in astronomy over the past century—not to mention the advent of human space travel—have provided huge amounts of data about what else is out there. For example, over Earth’s 4.567 billion year history, asteroids have hit our planet repeatedly. One of them caused the mass extinction that wiped out the dinosaurs.
In many ways, the things we found at Hell Creek exemplified these five big leaps. Spherules point to a massive asteroid impact. Crocodile bones and fossil palm fronds revealed that this region experienced a warmer climate in the past. We saw layers of rock that were 66 million years old. We compared and contrasted animal forms, including those of long-extinct dinosaurs. We looked out over marine deposits from an ancient inland sea that once covered North America’s Western Interior.
In fact, many of these themes will be apparent in our newly renovated Fossil Halls. When the National Museum of Natural History first opened its fossil halls in 1911, none of these scientific leaps had been made. Even as recently as 30 years ago, science hadn’t made the connection between carbon and climate change, and we had no idea just how dramatically an asteroid could impact life on Earth. There are so many exciting new stories to tell, and we can hardly wait to tell them. First up: the life, death, and discovery of dinosaurs from the Hell Creek Formation. This brand-new exhibition on the Last American Dinosaurs opened at the Museum on Nov. 25, 2014 and will remain on display while we renovate our fossil hall.
By Laura Donnelly-Smith and Juliana Olsson, Exhibits, National Museum of Natural History