Stephen Chester, an assistant professor of anthropology and paleontologist from Brooklyn College and the CUNY Graduate Center, was a key collaborator in a groundbreaking discovery that reveals in striking detail how the world and life recovered after the asteroid impact that wiped out the dinosaurs 66 million years ago.

Although the catastrophic event closed the door to dinosaurs, it sprung it wide open for mammals—and eventually humans—to grow into the dominant species we know today. The unprecedented find includes thousands of exceptionally preserved animal and plant fossils from the critical first million years after the catastrophe. Unearthed by a team of scientists in Colorado Springs, Colorado, the discovery shines a revelatory light on how life emerged from Earth’s darkest hour.

Chester, who specializes in the early evolutionary history of primates and other placental mammals, was instrumental in a peer-reviewed scientific paper in the recent issue of Science magazine (pdf). The discovery will also be highlighted in a NOVA documentary, Rise of the Mammals, streaming on PBS and airing on October 30.

Specifically, Chester and his colleagues identified fossil mammal species, calculated their body mass based on measurements of their skulls and teeth, and documented aspects of their anatomy to reconstruct behaviors such as their diets during the first million years after dinosaur extinction.

“This discovery unearthed complete skulls of many of these extinct mammals for the first time,” Chester said. “What makes this find even more amazing is that we also have many exceptionally preserved plant fossils that allow us to place these early mammals in an ecological context at a very high resolution through time. There are clear patterns linked with plants as mammals increased their species diversity and body mass rather quickly throughout the first million years after the mass extinction event. This discovery has produced a lifetime’s worth of fossils to work on, which will continue to provide us with a clearer view of the beginning of the age of mammals.”

This new and exceptional record combines plants, animals, and precise dates—a paleontological trifecta that paints a portrait of the emergence of the modern world.
Chester said that, overall, the study provides a better understanding of how life on Earth recovers following a mass extinction event, which has major and timely implications given that we are currently facing what many scientists call the sixth mass extinction today.

Tyler Lyson, the Denver Museum of Nature & Science’s curator of paleontology and department chair of earth sciences and lead author of the Science magazine paper, and Ian Miller, the museum’s curator of paleobotany and director of earth and space sciences, led the team that announced the discovery.

In addition to the Science paper, the story of the discovery is told in a new documentary, Rise of the Mammals, a NOVA production by HHMI Tangled Bank Studios for WGBH Boston, that will stream online beginning today across PBS platforms and mobile apps, and will broadcast nationally on PBS on October 30 at 9 p.m. EDT.

“The course of life on Earth changed radically on a single day 66 million years ago,” said Lyson. “Blasting our planet, an asteroid triggered the extinction of three of every four kinds of living organisms. While it was a really bad time for life on Earth, some things survived, including some of our earliest, earliest ancestors.”

Collaborators included:

  • David Krause, James Hagadorn, Antoine Bercovici, Farley Fleming, and Ken Weissenburger, Denver Museum of Nature & Science
  • Stephen Chester, Brooklyn College and the CUNY Graduate Center
  • William Clyde and Anthony Fuentes, University of New Hampshire
  • Greg Wilson, University of Washington
  • Kirk Johnson and Rich Barclay, National Museum of Natural History, Smithsonian Institution
  • Matthew Butrim, Wesleyan University
  • Gussie MacCracken, University of Maryland
  • Ben Lloyd, Colorado College