PNAS Science Sessions

How Snowball Earth melted

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, Shuhai Xiao explores how the Earth emerged from a planetwide glaciation called Snowball Earth.

In this episode, we cover: •[00:00] Introduction •[00:48] Geobiologist Shuhai Xiao introduces us to Snowball Earth. •[01:58] Xiao introduces the "plumeworld" hypothesis that describes the end of Snowball Earth. •[03:41] He explains how lithium isotopes in rocks can confirm the plumeworld hypothesis. •[05:54] Xiao explains why dolostone deposits in China were suitable for studying this hypothesis. •[06:53] He talks about the results of the study. •[07:39] He talks about the implications of the study results. •[08:26] Caveats and limitations of the study. •[10:06] Conclusion.

About Our Guests:

Shuhai Xiao Professor Virginia Tech

View related content here: https://www.pnas.org/doi/full/10.1073/pnas.2407419121

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Reverse development in a comb jelly

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, Joan Soto and Patel Burkhardt introduce us to a comb jelly with the ability to reverse its development to an earlier stage of life.

In this episode, we cover: •[00:00] Introduction •[00:54] Marine biologist Joan-Josep Soto recounts the history of research into reverse development. •[02:27] Soto and evolutionary biologist Burkhardt introduce the comb jelly Mnemiopsis leidyi and its life stages. •[04:04] Burkhardt explains why the researchers became interested in Mnemiopsis. •[04:48] Soto describes how the researchers induced reverse development in Mnemiopsis. •[06:13] Burkhardt explores hypotheses regarding why reverse development occurs. •[07:13] Soto talks about the lessons yet to be learned from Mnemiopsis. •[09:35] Burkhardt summarizes the caveats and limitations of the study. •[10:12] Conclusion.

About Our Guests:

Joan-Josep Soto-Angel Postdoctoral Scholar University Museum of Bergen

Pawel Burkhadt Group Leader Michael Sars Center, University of Bergen

View related content here: https://www.pnas.org/doi/10.1073/pnas.2411499121

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Air pollution and upward mobility

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, Luca Merlo and Francesca Dominici explore whether childhood exposure to air pollution can impact economic upward mobility as an adult.

In this episode, we cover: •[00:00] Introduction •[01:01] Statistician Luca Merlo talks about the background of the study. •[02:15] Merlo describes measurement of upward mobility in the study. •[03:36] Statistician Francesca Dominici explains the results. •[04:15] Dominici explores the variation in results across US counties. •[07:08] Merlo talks about the caveats and limitations of the study. •[08:14] Dominici lists the implications for policymakers. •[10:20] Conclusion.

About Our Guests: Luca Merlo Researcher European University of Rome

Francesca Dominici Professor Harvard T.H. Chan School of Public Health

View related content here: https://www.pnas.org/doi/abs/10.1073/pnas.2401882121

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Nationwide effects of smoke-related air pollution

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, Kai Chen explains the nationwide health effects of smoke-related fine particulate matter air pollution.

In this episode, we cover: •[00:00] Introduction •[01:07] Environmental epidemiologist Kai Chen introduces the health risks of fine particulate matter. •[02:20] Chen talks about trends in air pollution in the United States. •[03:56] He explains the study findings. •[05:51] Chen explores conditions that exacerbate smoke-related health effects. •[06:55] Chen talks about the caveats and limitations of the study. •[08:36] He lists the implications for policymakers and for the public. •[10:16] Conclusion.

About Our Guest: Kai Chen Associate Professor Yale School of Public Health

View related content here: https://www.pnas.org/doi/full/10.1073/pnas.2403960121

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Indigenous hunting and beluga populations

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, Max Friesen, Eline Lorenzen, and Mikkel Skovrind explore beluga population dynamics in relation to subsistence hunting by Indigenous communities in northern Canada.

In this episode, we cover: •[00:00] Introduction •[01:01] Archaeologist Max Friesen talks about the role of belugas in Inuvialuit culture. •[01:45] Evolutionary biologist Eline Lorenzen talks about the background of the study. •[02:26] Naturalist Mikkel Skovrind explains the methods of the study, including the sources of beluga samples and the methods of analysis. •[03:58] Skovrind introduces the results of the study, including the changing ratio of males to females harvested. •[06:07] Lorenzen describes the finding that genetic diversity of belugas had not declined over time. •[06:59] Friesen and Lorenzen talk about what the study reveals, and suggests, about past hunting methods. •[08:09] The authors explain the caveats and limitations of the study. •[09:05] Skovrind and Friesen explore the implications of the study for traditional subsistence hunting practices. •[10:19] Conclusion

About Our Guests:

Max Friesen Professor University of Toronto

Eline Lorenzen Professor University of Copenhagen

Mikkel Skovrind Postdoctoral researcher Lund University

View related content here: https://www.pnas.org/doi/full/10.1073/pnas.2405993121

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The neuroscience of music perception

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, Petri Toiviainen, Ibi Burunat, and Daniel Levitin describe the neuroscience of how musicians and non-musicians perceive boundaries within pieces of music.

In this episode, we cover: •[00:00] Introduction •[01:04] Music neuroscientist Petri Toiviainen, music neuroscientist Ibi Burunat, and cognitive neuroscientist Daniel Levitin introduce the concept of musical boundaries. •[02:29] Toiviainen and Burunat tell about the musical pieces used in the experiment, as well as the experimental setup. •[04:05] Levitin explains why musicians and non-musicians were included in the study. •[04:27] Burunat and Levitin talk about the findings generally. •[05:50] Toiviainen and Levitin explain how musicians and non-musicians' responses to the music differed. •[07:13] Toiviainen and Burunat talk about the caveats and limitations of the study. •[08:59] Levitin and Burunat explore the implications of the work for music neuroscience. •[09:46] Conclusion.

About Our Guests:

Petri Toiviainen Professor University of Jyväskylä

Ibi Burunat Postdoctoral researcher University of Jyväskylä

Daniel Levitin Professor emeritus McGill University

View related content here: https://www.pnas.org/doi/10.1073/pnas.2319459121

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How python hearts grow and shrink

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, Leslie Leinwand, of the University of Colorado in Boulder, and Claudia Crocini, of Charité – Berlin University of Medicine in Germany, describe how the hearts of constricting pythons change size after meals.

In this episode, we cover: •[00:00] Introduction •[01:19] What is the natural context for cardiac hypertrophy in constricting pythons? •[02:48] What were the mechanisms involved in this process that you identified? •[05:27] What did you discover about the mechanisms of heart size regression in these snakes? •[07:24] What are the next steps in this line of research? •[08:21] Conclusion.

About Our Guest: Leslie Leinwand Professor University of Colorado

Claudia Crocini Junior Research Group Leader Charité – Berlin University Medicine

View related content here: https://www.pnas.org/doi/full/10.1073/pnas.2322726121

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How people travel to racially different neighborhoods

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, Mario Small talks about patterns of people's travel to neighborhoods racially different than their home neighborhood.

In this episode, we cover: •[00:00] Introduction •[00:59] Sociologist Mario Small describes how everyday travel can temper residential segregation. •[01:57] Small talks about how their study tracked peoples' movements and defined travel beyond a person's racial comfort zone. •[03:48] Small explains the study's results. •[06:08] He explores why some destinations take people to racially similar neighborhoods and some take people to racially different neighborhoods. •[07:15] Small shows how "15-minute cities" might inadvertently reinforce residential segregation. •[08:21] He lists the caveats and limitations of the study. •[10:34] Conclusion.

About Our Guest:

Mario Small Quetelet Professor of Social Science Columbia University

View related content here: https://www.pnas.org/doi/10.1073/pnas.2401661121

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How pathogen stowaways traversed the oceans

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, Jamie Lloyd-Smith and Elizabeth Blackmore describe how they modeled the epidemiology of pathogens on ocean voyages.

In this episode, we cover: •[00:00] Introduction •[01:04] Integrative scientist Jamie Lloyd-Smith and disease ecologist Elizabeth Blackmore describe how they came to study the epidemiology of ocean travel. •[03:21] Blackmore and Lloyd-Smith explain why they focused on three pathogens: influenza, measles, and smallpox. •[04:13] Lloyd-Smith explains the results of the disease model, with pathogen biology, passenger number, and journey length factoring into the duration of shipboard outbreaks. •[05:05] Blackmore details the additional insights provided by newspaper records of ship arrivals in 1850s San Francisco. •[06:57] Lloyd-Smith and Blackmore talk about the caveats and limitations of the study. •[08:02] Blackmore and Lloyd-Smith explore potential next steps. •[09:47] Conclusion.

About Our Guests:

Jamie Lloyd-Smith Professor University of California, Los Angeles

Elizabeth Blackmore Doctoral student Yale University

View related content here: https://www.pnas.org/doi/10.1073/pnas.2400425121

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Why "Tornado Alley" is unique to North America

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, Funing Li and Dan Chavas explain why North America produces many tornadoes each year and South America does not.

In this episode, we cover: •[00:00] Introduction •[01:01] Weather and climate scientist Funing Li talks about the frequency of tornadoes within and outside of the United States. •[01:25] Li explains the geography of severe thunderstorm hotspots in North and South America. •[02:46] Weather and climate scientist Dan Chavas and Li describe how they became interested in the effect of surface geography on tornadoes. •[05:13] Li and Chavas explain their modeling approach. •[07:23] Li and Chavas talk about why surface roughness is important for tornado formation. •[08:14] Chavas and Li describe the implications of the study, including effects of climate change and insights into paleoclimate. •[09:43] Caveats and limitations of the study. •[10:26] Conclusion.

About Our Guests:

Funing Li Postdoctoral associate Massachusetts Institute of Technology

Dan Chavas Associate professor Purdue University

View related content here: https://www.pnas.org/doi/10.1073/pnas.2315425121

Follow us on Spotify, Apple Podcasts, YouTube, or wherever you get your podcasts for more captivating discussions on scientific breakthroughs!

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