Island of the tool users
Many Minds
Tool use is rare in the animal kingdom—but maybe not as rare as we once thought. Since Jane Goodall famously observed a chimpanzee fishing for termites, many new examples of animals using tools have come to light. Birds using sticks to forage for grubs. Sea otters using rocks to smash open mussels. Digger wasps using stones to close off their burrows. But as these examples mount, so do the scientific questions. What is tool use, really? What different forms does it take? Does it always imply a high degree of intelligence? And perhaps the biggest question of all: Why do some creatures use...
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Cognitive offloading and its consequences
Many Minds
For thousands of years—maybe for as long as we've been human—we've offloaded our thinking. We've counted on our fingers. We've carved tallies into bone. We've invented a long series of tools to help us reason, remember, and manage information—tools like abacuses, calendars, writing systems, calculators, smartphones, and many, many more. So cognitive offloading is hardly new—but the questions around it seem newly urgent. As cognitive technologies accumulate, as opportunities for offloading tempt us at every turn, as headlines warn of "digital dementia" and "cognitive surrender," it...
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Coming of age in Ngogo
Many Minds
It's a familiar story in many ways. A child is born, and for years afterward is adored and indulged and anchored to home and family. But then the child grows up and starts crossing that long threshold into adulthood. The transition proves—to say the least—a bit turbulent. Now when I say this story is familiar, I don't just mean familiar to us as human beings. After all, a similar story has long played out among our closest cousins, the chimpanzees. My guest today is . Rachna co-directs the longstanding in Uganda and is an incoming Assistant Professor of Psychology at the University of...
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The natural history of linguistic diversity
Many Minds
Thousands of languages are used around the world today, and this linguistic diversity is a precious part of our human heritage. But it's also more than that. Linguistic diversity provides clues—a vast crazy quilt of clues—about how language works, about how history has unfolded, about the dynamics of culture, and about the nature of the human mind. My guest today is . Damián is an based at the at the Pompeu Fabra University in Barcelona. Over the last decade or so, Damián’s emerged as one of the most innovative researchers in the study of language and linguistic diversity. He’s...
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From the archive: Electric ecology
Many Minds
Hi friends! We're still taking a bit of a summer pause. We'll be back at the end of August—in the meanwhile, enjoy this listener favorite from our archives! ----- [originally aired September 19, 2024] There's a bit of a buzz out there, right now, but maybe you haven’t noticed. It's in the water, it's in the air. It's electricity—and it's all around us, all the time, including in some places you might not have expected to find it. We humans, after all, are not super tuned in to this layer of reality. But many other creatures are—and scientists are starting to take note. My guest today...
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From the archive: Varieties of childhood
Many Minds
Hi friends! We're taking a bit of a summer pause. We'll be back soon—in the meanwhile, enjoy this listener favorite from our archives! ----- [originally aired July 10, 2025] Childhood is a special time, a strange time. Children are adored and catered to—they're given their own menus and bedrooms. They're considered delicate and precious, and so we cushion them from every imaginable risk. Kids are encouraged to play, of course—but very often it's under the watchful eye of anxious adults. This, anyway, is how childhood looks in much of the United States today. But is this the way childhood...
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From the archive: Philosophers on psychedelics
Many Minds
Hi friends! We're taking a bit of a summer pause. We will be back soon—in the meanwhile, enjoy this listener favorite from our archives! ----- [originally aired May 14, 2025] Some call it the "psychedelic renaissance." In the last decade or so, interest in psychedelic drugs has surged—and not just among Silicon Valley types and psychiatrists and neuroscientists. It's also surged among a stereotypically soberer crowd: academic philosophers. The reasons are clear. With their varied and sometimes transformative effects, psychedelics raise ethical questions, epistemological questions,...
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The origins of Darwin's ideas
Many Minds
No discipline, no sphere of intellectual life, has been untouched by the work of Charles Darwin. He died in 1882 but his ideas are very much alive; they're now central to how we understand the natural world, the human mind, non-human minds, plants, biogeography, morality and emotion, culture, language, and more. But where did his ideas come from? How did they grow out of his travels, his social circle, his hobbies, his particular cast of mind? My guest today is . Janet is Professor Emerita at Harvard University in the department of the History of Science. She is perhaps best known for...
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The sparkling deep
Many Minds
It’s tempting to see bioluminescence as an oddity, one of those rare eccentricities of life on earth. And, on land, maybe that’s true. But our planet is mostly water, and out in the open ocean bioluminescence is utterly commonplace. Creatures of all shapes and sorts sparkle and glow, glitter and pulse. But what are these displays for? Why did they evolve? How did light become the currency of the deep? My guest today is . Sönke is a Distinguished Professor of Biology at Duke University, where he and his research group study the visual ecology of the ocean. He’s the author of...
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Is Man the Hunter just a myth?
Many Minds
There's a story about of our past that you know well. It goes like this: At some point earlier in human evolution, we started to hunt. Men in particular—perhaps channeling some deep-seated aggressive impulses—began to seek out big game. This new food source, this bonanza of calories, was what allowed our brains to expand. It changed our bodies and our societies and sent our species off on a whole new track. In short, Man the Hunter made us human. This story—told in different versions, with different points of emphasis—has circulated for decades. It's been debunked and revived, rejected...
info_outlineIt’s tempting to see bioluminescence as an oddity, one of those rare eccentricities of life on earth. And, on land, maybe that’s true. But our planet is mostly water, and out in the open ocean bioluminescence is utterly commonplace. Creatures of all shapes and sorts sparkle and glow, glitter and pulse. But what are these displays for? Why did they evolve? How did light become the currency of the deep?
My guest today is Dr. Sönke Johnsen. Sönke is a Distinguished Professor of Biology at Duke University, where he and his research group study the visual ecology of the ocean. He’s the author of a number of books: most recently Into the Great Wide Ocean, about life in the pelagic realm, and The Radiant Sea, a photographic tour of bioluminescence and color, written in collaboration with Dr. Steven Haddock.
Here, Sönke and I talk about the open ocean: the most common habitat on our planet, yet one that many people will never experience. We consider the curious distribution of bioluminescence— rare on land, exceptionally prevalent in the ocean, and all but absent in freshwater. We talk about how bioluminescence seems to have evolved—many, many times over in fact. We survey the functions of making light in the deep—from counter-illumination to courtship to revenge. Finally, we consider what Sönke takes to be the biggest remaining puzzle about bioluminescence at sea.
Alright friends, if you’re enjoying Many Minds, we ask (humbly) if you would think about rating us, reviewing us, leaving us a comment, boosting us on social media, or perhaps haranguing your friends—relentlessly—until they give us a listen.
Without further ado, onto my conversation with Dr. Sönke Johnsen. Enjoy!
Notes
3:30 – The scientific report by Dr. Johnsen and colleagues describing the bioluminescent octopus, Stauroteuthis syrtensis.
12:00 – A popular article on the bristlemouth. The article reports a scientist's estimate of “as many as a dozen [bristlemouths] per square meter of ocean.”
15:00 – A recent discussion of the “burglar alarm hypothesis.”
18:00 – The website for the Johnsen Lab at Duke University.
24:00 – A chart and discussion of the depth zones of the ocean.
29:30 – A study by Séverine Martini and Steven Haddock quantifying the prevalence of bioluminescence at different depths. A popular write-up of the same study.
33:00 – A popular article on vertical migration in the ocean, also called “diel vertical migration.” A recent scientific study of the phenomenon.
39:00 – A recent article on the evolution of bioluminescence.
45:00 – For detailed scientific discussion of the physical basis of bioluminescence, fluorescence, and other phenomena we discuss, see Dr. Johnson’s book, The Optics of Life.
52:00 – For previous episodes on the use of sound in the animal kingdom, see here and here. For our previous episode on electroreception and electric ecology (including in marine organisms), see here.
57:00 – For more on the functions of bioluminescence, see here. For a report of a recently discovered function of bioluminescence, see here.
1:03:00 – An article by Dr. Johnsen about the different colors of bioluminescence present in the deep sea.
1:05:00 – A video of ostracod mating displays.
1:08:00 – For our recent episode on cave art, see here.
1:16:00 – For our earlier episode on firefly synchronization, see here.
Recommendations
Website and review article by Steven Haddock
The lab of Todd Oakley
Below the edge of darkness, Edie Widder
Tile art credit: Image by Georgi Kalaydzhiev via Unsplash
Many Minds is a project of the Diverse Intelligences Summer Institute, which is made possible by a generous grant from the John Templeton Foundation to Indiana University. The show is hosted and produced by Kensy Cooperrider, with help from Assistant Producer Urte Laukaityte and with creative support from DISI Directors Erica Cartmill and Jacob Foster. Our artwork is by Ben Oldroyd.
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