The researchers analyzed teeth from rodents that lived during the Paleocene-Eocene Thermal Maximum (PETM), a period of global warming that occurred about 56 million years ago. The teeth showed signs of wear that indicate the animals were eating grasses, rather than the fruits and leaves that were more common in the rainforest environment that dominated the Earth at the time.
"This is the first evidence we have for grasslands during the PETM, and it's also the earliest evidence for grasslands anywhere in the world," said lead author Tyler Faith, a PhD candidate in the Department of Organismal Biology and Anatomy at UChicago. "It suggests that grasslands may have originated in North America, rather than in Africa as previously thought."
The discovery of these ancient rodents also helps to shed light on the evolution of grasses. Grasses are one of the most important plant groups on Earth, and they play a vital role in the food chain. However, the evolutionary history of grasses is relatively poorly understood.
"This find helps us to better understand how grasses evolved and spread across the globe," said Faith. "It also provides new insights into the ancient climate and environment of North America."
The researchers believe that the grasslands that emerged during the PETM may have been a result of the warmer and drier climate conditions that prevailed at the time. As the climate changed, rainforests began to give way to more open habitats, such as grasslands and savannas. This change in vegetation had a profound impact on the animals that lived in the region, and it may have played a role in the extinction of many large mammals.
The researchers hope that their findings will encourage other scientists to look for evidence of ancient grasslands in other parts of the world. "We think it's likely that grasslands originated in multiple places around the globe," said Faith. "By studying the fossil record, we can learn more about the history of these important ecosystems and the role they played in the evolution of life."
