PNAS Science Sessions

Latest Episodes:

Air pollution and pet health Nov 24, 2025

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Air quality and pet health

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, Stephen Jarvis explores the health impacts of poor air quality on pets.

In this episode, we cover: •[00:00] Introduction •[00:51] Environmental economist Stephen Jarvis explains how he became interested in the effects of air quality on pets. •[01:59] He talks about the similarities in exposure between humans and pets, and introduces the veterinary dataset used in the study. •[03:30] Jarvis explains the results of the study and the potential physiological effects of poor air quality. •[05:40] He talks about the implications of reducing air pollution for petcare and the takeaway messages of the study. •[08:17] Jarvis explains the caveats and limitations of the study. •[09:14] Conclusion.

About Our Guest:

Stephen Jarvis Assistant professor London School of Economics

View related content here: https://www.pnas.org/doi/10.1073/pnas.2504553122

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Probing the die-off of Pacific oysters Nov 10, 2025

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A giant virus associated with oyster aquaculture mortality

In this episode, Curtis Suttle and Kevin Xu Zhong explain how a previously unidentified virus may be connected to mass die-offs of farmed Pacific oysters.

In this episode, we cover:

• [00:00] Introduction • [01:03] Environmental virologist Curtis Suttle introduces the importance of the Pacific oyster to aquaculture. • [01:42] Suttle describes mass mortality events, including one he witnessed. • [02:42] Environmental microbiologist Kevin Xu Zhong talks about the methods used to identify the Pacific Oyster Nidovirus 1. • [03:53] Zhong describes the notable features of the nidovirus. • [05:19] Zhong and Suttle explain how the nidovirus merits designation of a nidovirus family. • [06:25] Suttle explores the takeaways for oyster farmers and regulators. • [08:15] He lists the caveats and limitations of the study. • [09:40] Conclusion.

About Our Guests:

Kevin Xu Zhong Research Associate University of British Columbia

Curtis Suttle Professor University of British Columbia

View related content here: https://www.pnas.org/doi/10.1073/pnas.2426923122

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Swamp lights and bat sight Oct 27, 2025

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Swamp lights and bat sight

In this episode, researchers explore two spooky mysteries: the source of will-o'-the-wisps and how bats integrate vision with echolocation.

In this episode, we cover: •[00:00] Introduction •[00:58] Richard Zare's background and expertise. •[01:26] Richard, have you ever seen will-o'-the-wisps in the wild? •[01:31] What did we already know about will-o'-the-wisps before your study? •[02:42] How could water droplets ignite methane? •[03:24] Tell us about the methods of your study. How did you explore this phenomenon? •[04:17] What are the broader implications of your findings, beyond just will-o'-the-wisps? •[05:20] What are the caveats or the limitations of the study? •[05:40] Laura Stidsholt's background and expertise. •[06:06] Laura, what can you tell us about the species you studied? •[06:25] What instruments did you attach to the bats? •[07:03] How did the bats' echolocation behavior compare in dark versus lit environments? •[08:14] What do the results suggest about the benefits of integrating information from multiple senses while hunting prey? •[08:58] What do the results imply about the potential impact of artificial light on bats? •[09:43] Final thoughts and conclusion.

About Our Guests: Richard Zare Marguerite Blake Wilbur Professor of Natural Science Stanford University

Laura Stidsholt Assistant Professor Aarhus University

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Enzyme linked with brain evolution Oct 13, 2025

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Implications of a mutation in modern humans

In this episode, Xiangchun Ju and Svante Pääbo explore the evolutionary implications of a mutation that separates modern humans from ancestral hominins.

In this episode, we cover: •[00:00] •[01:22] Neurobiologist Xiangchun Ju introduces the enzyme adenylosuccinate lyase, or ADSL, and its role in the synthesis of purine. •[02:09] Evolutionary anthropologist Svante Pääbo talks about the discovery of the A429V mutation, which is present in modern humans but not Neanderthals or Denisovans. •[03:38] Ju and Pääbo talk about the methods to humanize mice in order to study the evolutionary importance of the A429V mutation. •[05:04] They explain the results of the behavioral studies of the humanized mice. •[06:27] Pääbo explores the takeaways from the study. •[08:05] He contextualizes the study alongside other studies of modern human development. •[09:17] Pääbo and Ju list the caveats and limitations of the study. •[10:14] Conclusion.

About Our Guests:

Xiangchun Ju Postdoctoral scholar Okinawa Institute of Science and Technology

Svante Pääbo Director Max Planck Institute for Evolutionary Anthropology

View related content here: https://www.pnas.org/doi/10.1073/pnas.2508540122

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Where primates evolved Sep 29, 2025

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Where primates evolved

In this episode, Jorge Avaria-Llautureo and Chris Venditti explain why the evolution of primates likely occurred in cold, dry climates rather than in tropical forests.

In this episode, we cover: •[00:00] Introduction •[00:58] Evolutionary biologist Jorge Avaria-Lautureo explains the prevailing hypothesis that primates evolved in a tropical climate •[02:54] Evolutionary biologist Chris Venditti introduces evidence suggesting a different origin climate. •[03:54] Avaria discusses how the researchers reconstructed the climate of early primate species. •[05:05] Venditti and Avaria explain why it was important to use standardized climate definitions in this study. •[07:29] Avaria describes the results of the study. •[08:18]Venditti talks about the importance of understanding early primates' climates. •[09:21] Avaria and Venditti talk about the study's caveats and limitations. •[10:22] Conclusion.

About Our Guests:

Jorge Avaria-Llautureo Postdoctoral scholar University of Reading

Chris Venditti Professor University of Reading

View related content here: https://www.pnas.org/doi/10.1073/pnas.2423833122

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How climate change alters lake oxygen levels Sep 15, 2025

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Climate change and lake oxygenation

In this episode, Joachim Jansen explains how climate change altered cycles of oxygenation in lakes.

In this episode, we cover: •[00:00] Introduction. •[00:56] Limnologist Joachim Jansen introduces us to the cycles of oxygenation in lakes throughout the seasons. •[02:35] He describes previous hypothesis about climate change and lake oxygenation and introduces the methods and datasets of the study. •[04:59] Jansen introduces the results of the study, including key differences between large and small lakes. •[06:54] He talks about the consequences of deoxygenation. •[09:03] Jansen explains the caveats and limitations of the study. •[09:37] Conclusion.

About Our Guest:

Joachim Jansen Postdoctoral Researcher University of Helsinki

View related content here: https://www.pnas.org/doi/10.1073/pnas.2426140122

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Unpacking the unreturnable squash nick shot Sep 01, 2025

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The physics of the squash nick shot

In this episode, Roberto Zenit explains the physics behind the unanswerable nick shot in the game of squash.

In this episode, we cover: •[00:00] Introduction. •[00:56] Engineer Roberto Zenit introduces the game of squash, including his participation in the sport, and introduces the nick shot. •[02:11] He talks about the background and methods of the study. •[04:50] Zenit describes the mechanics of a nick shot. •[06:01] He talks about the implications of the study for squash players and for other applications. •[08:52] Zenit recounts the caveats and limitations of the study. •[09:41] Conclusion.

About Our Guests:

Roberto Zenit Professor Brown University

View related content here: https://www.pnas.org/doi/10.1073/pnas.2505715122

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North America's oldest pterosaur fossil Aug 18, 2025

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A pterosaur and its ecosystem at the end of the Triassic

In this episode, Kay Behrensmeyer and Ben Kligman describe what a fossil bone bed in Arizona reveals about a 209-million-year-old pterosaur and its ecosystem.

In this episode, we cover: •[00:00] Introduction •[01:01] Paleoecologist Kay Behrensmeyer and paleontologist Ben Kligman describe the discovery of this fossil bone bed. •[03:10] Kligman and Behrensmeyer introduce a previously undescribed pterosaur. •[05:00] They talk about what this specimen says about the ecology and evolution of pterosaurs. •[06:15] Kligman and Behrensmeyer talk about the importance of studying this fossil community. •[07:52] They explain how their methods can improve paleontology and discovery of small fossils. •[09:08] Behrensmeyer and Kligman talk about the study's caveats and limitations. •[10:10] Conclusion.

About Our Guests:

Kay Behrensmeyer Curator of Paleobiology National Museum of Natural History, Smithsonian Institution

Ben Kligman Postdoctoral Fellow National Museum of Natural History, Smithsonian Institution

View related content here: https://www.pnas.org/doi/10.1073/pnas.2505513122

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Exploring the origins of a glacial relict seal Aug 04, 2025

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The postglacial history of the Saimaa ringed seal

In this episode, Jaakko Pohjoismäki, Jukka Jernvall, and Ari Löytynoja discuss the evolutionary history of the Saimaa ringed seal.

In this episode, we cover: •[00:00] Introduction •[01:06] Molecular biologist Jaakko Pohjoismäki introduces Lake Saimaa and the Saimaa ringed seal. •[02:30] Zoologist Jukka Jernvall talks about the characteristics of species isolated by glaciation. •[03:27] Evolutionary biologist and bioinformatician Ari Löytynoja explains the genetic and demographic methods of the study. •[04:11] Löytynoja and Jernvall explain why the results were surprising and where the study turned next. •[06:20] Pohjoismäki and Löytynoja describe the study's implications for biodiversity in postglacial habitats. •[07:50] Jernvall and Löytynoja talk about the study's caveats and limitations. •[10:14] Conclusion.

About Our Guests:

Jaakko Pohjoismäki Professor University of Eastern Finland

Jukka Jernvall Professor University of Helsinki

Ari Löytynoja University Lecturer University of Helsinki

View related content here: https://www.pnas.org/doi/abs/10.1073/pnas.2503368122

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Conservation of the Eastern Black Rhinoceros Jul 21, 2025

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Managing eastern black rhinoceros populations with genetic studies

In this episode, Barbara Mable and Ronald Mellya show how allowing endangered rhinos to move between populations enhances genetic diversity.

In this episode, we cover: •[00:00] Introduction •[01:00] Evolutionary geneticist Barbara Mable explains why is genetic diversity important in managing small, isolated populations of rhinos. •[02:59] Park warden Ronald Mellya describes how his firsthand experience with rhino management led to this study. •[04:52] Mable explains the methods of the study and the contributions of co-author Anubhab Khan. •[06:20] Mable talks about the results. •[07:24] Mellya tells how the study has changed rhino management in Tanzania. •[08:37] Mable and Mellya enumerate the caveats and limitations of the study. •[10:20] Conclusion.

About Our Guests:

Barbara Mable Professor University of Glasgow

Ronald Mellya Park Warden Tanzania National Parks

View related content here: https://www.pnas.org/doi/abs/10.1073/pnas.2414412122

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