What Humans Would Face in the Cretaceous: A Science Friday Dinosaur Reality Check

Overview

In an emergency Science Friday taping, Flora Lichtman talks with paleontologist Steve Persatti about what a person would notice if an ordinary suburban neighborhood were suddenly sucked back to the late Cretaceous. They discuss the ecology of dinosaurs, the warmer air due to higher carbon dioxide, and how the absence of grasses would shape the landscape. They also consider viral and bacterial infections in deep time, and what that could mean for modern humans in such a world. The conversation ties together film fiction with fossil evidence to build a plausible, though speculative, sense of life in a world dominated by T rex, teeth-bearing birds, and early grasses.

Key insights

• Dinosaurs, birds with teeth and claws, and pterosaurs would be prominent, while mammals would be small and rare.
• The atmosphere would be warmer due to elevated carbon dioxide, complicating breathing for a modern human.
• Fossil bones bearing signs of infections suggest ancient viruses and bacteria could pose risks across time.
• The discussion centers on the imagined last day before a mass extinction and what that moment would feel like.

Introduction and premise

The podcast opens with Flora Lichtman framing an imaginative scenario inspired by a film about a suburban Michigan neighborhood pulled into a prehistoric world. The guest, paleontologist Steve Persatti, joins to answer practical questions about what a modern person would notice and experience in the Cretaceous period. The conversation blends movie critique with solid paleontological concepts, grounding speculation in recent research while maintaining a sense of cinematic curiosity.

What the world would look like in the late Cretaceous

Persatti begins by outlining the most conspicuous features a traveler would notice. Chasing would likely include numerous theropods such as T. rex, along with other large dinosaurs. Birds would be present but distinct, featuring teeth and talons that echo their dinosaur ancestry. Pterosaurs would fill the skies, and mammals would be comparatively scarce, existing as small, inconspicuous creatures. The landscape would lack grasslands, prairies, or savannas; although some grasses were evolving, they had not yet reshaped the terrain in the way they would later. In addition to visual cues, an atmosphere noticeably different from today would alter the experience of daily life.

Atmospheric conditions and climate

The discussion turns to air quality and temperature. The end of the Cretaceous period was warmer overall, largely due to higher atmospheric carbon dioxide. Persatti cites a recent study combining paleontology and chemistry that analyzed enamel from fossilized dinosaur teeth. The enamel records provide a paleothermometer—a proxy for ancient temperatures and, by extension, CO2 levels. The findings suggest carbon dioxide was several times higher than today, with estimates that parts of the period featured CO2 three times current levels. Even toward the end, CO2 remained elevated, potentially double today’s concentration. The takeaway is that such an atmosphere would alter respiration and physical exertion, making everyday activity more strenuous for a modern human in that climate.

The host relates cycling and hill-climbing on Earth today to the potential breathlessness in a hotter, CO2-rich air. Persatti emphasizes that while it would be possible to breathe the air, it would be more challenging, especially for physically demanding tasks.

Health, disease, and cross-species risks

Turning to disease, Persatti notes that the fossil record offers indirect evidence of infections. Fossil bones can show signs of infection consistent with certain viruses or bacterial infections observed in modern birds and other animals. While viruses themselves don’t fossilize, their skeletal manifestations can be compared to known disease signatures. The discussion acknowledges the potential for cross-species disease risks in a dinosaur-dominated world, highlighting how disease dynamics would differ in a vastly different ecosystem and climate.

Choosing a time and place to visit

In the closing minutes, Lichtman asks Persatti where and when he would go if given a wormhole. He expresses a desire to witness the last day of the Cretaceous, morning light on a world with towering dinosaurs in a state of sudden change, just before the asteroid impact that would reshape life on Earth. This imagined moment blends a sense of wonder with a sobering awareness of planetary-scale change.

Closing credits and reflections

The episode closes with credits to Persatti as the author of a history of birds, and a light note about a faux science fact check line and a hotline number for quick science questions. Flora Lichtman signs off, inviting listeners to explore the science behind blockbuster films and beyond.