Human beings like to divide themselves into groups, and then cooperate, socialize, and reproduce with members of their own group. But they’re not very absolutist about it; groups tend to gradually (or suddenly) intermingle, as people explore, intermarry, or conquer each other. David Reich has pioneered the use of genetic data in uncovering the history of ancient humanity: what groups existed where and when, and how they interacted. The result is a picture of churning populations in constant flux, including “ghost populations” that no longer exist today.

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David Reich received his Ph.D. in zoology from the University of Oxford. He is currently a professor of genetics at Harvard Medical School. Among his awards are the Dan David Prize, the National Academy of Sciences Award in Molecular Biology, the Wiley Prize, the Darwin-Wallace Medal, and the Massry Prize. He is the author of Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past.

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Are numbers real? What does that even mean? You can’t kick a number. But you can talk about numbers in useful ways, and we use numbers to talk about the real world. There’s surely a kind of reality there. On the other hand, Luke Skywalker isn’t a real person, but we talk about him all the time. Maybe we can talk about unreal things in useful ways. Jody Azzouni is one of the leading contemporary advocates of nominalism, the view that abstract objects are not “things,” they are merely labels we use in talking about things. A deeply philosophical issue, but one that has implications for how we think about physics and the laws of nature.

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Jody Azzouni received his Ph.D. in philosophy from the City University of New York. He is currently a professor of philosophy at Tufts University. In addition to his philosophical work, he is an active writer of fiction and poetry.

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• Tufts web page
• PhilPeople profile
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• Wikipedia
• PoemHunter page

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As each December comes to a close, we wrap up another year of podcasts with the Mindscape Holiday Message. Nothing too profound, just some thoughts that wouldn’t fit easily into a regular podcast. This year we’re talking about academic disciplines and cocktails. What do they have in common, you may ask? Listen and find out!

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Mindscape will be dark on Monday December 27, and will resume regular programming on Monday January 3. Here are the two books I mentioned in the podcast, and the one essay:

• The Aviary Cocktail Book
• Death & Co Modern Classic Cocktails
• Steven Weinberg, “Against Philosophy”

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Welcome to the December 2021 Ask Me Anything episode of Mindscape! These monthly excursions are funded by Patreon supporters (who are also the ones asking the questions). I take the large number of questions asked by Patreons, whittle them down to a more manageable size — based primarily on whether I have anything interesting to say about them, not whether the questions themselves are good — and sometimes group them together if they are about a similar topic. Note that there will be no January AMA, for purposes of a holiday break. Enjoy!

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When it comes to thinking about quantum mechanics, there are levels. One level is shut-up-and-calculate: find a wave function, square it to get a probability. One level is foundational: dig deeply into the underlying ontology. But there’s a level in between, long neglected but recently coming to life. In this level you think about — or do experiments with — entangled quantum systems in the real world, putting entanglement to use. Monika Schleier-Smith is an experimental physicist specializing in cold atoms, which can be both entangled and manipulated. We discuss how to use such systems to study everything from metrology to quantum gravity.

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Monika Schleier-Smith received her Ph.D. in physics from the Massachusetts Institute of Technology. She is currently an Associate Professor of Physics at Stanford University. Among her awards are a MacArthur Fellowship, a Sloan Fellowship, and the I. I. Rabi Prize in Atomic, Molecular, and Optical Physics from the American Physical Society.

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We all know you can’t derive “ought” from “is.” But it’s equally clear that “is” — how the world actual works — is going to matter for “ought” — our moral choices in the world. And an important part of “is” is who we are as human beings. As products of a messy evolutionary history, we all have moral intuitions. What parts of the brain light up when we’re being consequentialist, or when we’re following rules? What is the relationship, if any, between those intuitions and a good moral philosophy? Joshua Greene is both a philosopher and a psychologist who studies what our intuitions are, and uses that to help illuminate what morality should be. He gives one of the best defenses of utilitarianism I’ve heard.

Bonus! Joshua is a co-founder of Giving Multiplier, an effective-altruism program that lets you donate to your personal favorite causes and also get matching donations to charities that have been judged to be especially effective. He was kind enough to set up a special URL for Mindscape listeners, where their donations will be matched at a higher rate of up to 100%. That lets you get matching donations when you donate to a personal favorite cause along with a charity that has been judged to be especially effective. Check out https://givingmultiplier.org/mindscape.

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Joshua Greene received his Ph.D. in philosophy from Princeton University. He is currently Professor of Psychology and a member of the Center for Brain Science faculty at Harvard University. His an originator of the dual-process model of moral reasoning. Among his awards are the the Stanton Prize from the Society for Philosophy and Psychology and Harvard’s Roslyn Abramson Award for teaching. He is the author of Moral Tribes: Emotion, Reason, and the Gap Between Us and Them.

• Web site
• Harvard web page
• Google Scholar publications
• Wikipedia
• Giving Multiplier

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We’ve talked about the very origin of life, but certain transitions along its subsequent history were incredibly important. Perhaps none more so than the transition from unicellular to multicellular organisms, which made possible an incredible diversity of organisms and structures. Will Ratcliff studies the physics that constrains multicellular structures, examines the minute changes in certain yeast cells that allows them to become multicellular, and does long-term evolution experiments in which multicellularity spontaneously evolves and grows. We can’t yet create life from non-life, but we can reproduce critical evolutionary steps in the lab.

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William Ratcliff received his Ph.D. in Ecology, Evolution, and Behavior at the University of Minnesota. He is currently Associate Professor in the School of Biological Sciences at Georgia Tech. Among his awards are a Packard Fellowship and being named in Popular Science‘s “Brilliant 10” of 2016.

• Web site
• Google Scholar publications
• Packard Foundation bio
• Twitter
• “Experimental Evolution of Multicellularity,” Ratcliff et al. (2012)
• “De Novo Evolution of Macroscopic Multicellularity,” Bozdag et al. (2021)

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Mathematics is often thought of as the pinnacle of crisp precision: the square of the hypotenuse of a right triangle isn’t “roughly” the sum of the squares of the other two sides, it’s exactly that. But we live in a world of messy imprecision, and increasingly we need sophisticated techniques to quantify and deal with approximate statistical relations rather than perfect ones. Modern mathematicians have noticed, and are taking up the challenge. Tai-Danae Bradley is a mathematician who employs very high-level ideas — category theory, topology, quantum probability theory — to analyze real-world phenomena like the structure of natural-language speech. We explore a number of cool ideas and what kinds of places they are leading us to.

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Tai-Danae Bradley received her Ph.D. in mathematics from the CUNY Graduate Center. She is currently a research mathematician at Alphabet, visiting research professor of mathematics at The Master’s University, and executive director of the Math3ma Institute. She hosts an explanatory mathematics blog, Math3ma. She is the co-author of the graduate-level textbook Topology: A Categorical Approach.

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• Twitter
• Video introduction to “At the Interface of Algebra and Statistics” Ph.D. thesis

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Welcome to the November 2021 Ask Me Anything episode of Mindscape! These monthly excursions are funded by Patreon supporters (who are also the ones asking the questions). I take the large number of questions asked by Patreons, whittle them down to a more manageable size — based primarily on whether I have anything interesting to say about them, not whether the questions themselves are good — and sometimes group them together if they are about a similar topic. Enjoy!

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It’s a well-worn cliché that oceans cover seventy percent of the surface of Earth, but we tend to give them secondary consideration when thinking about the environment. But climate change is wreaking havoc on the oceans, not to mention pollution and overfishing — 90% of the world’s marine fish stocks are fully exploited or depleted. Today’s guest, Sylvia Earle, is a well-known ocean scientist, a celebrated underwater explorer, and a tireless advocate for the world’s oceans. We talk about the current state of our oceans, what we know and have yet to learn about them, and what we can do individually and collectively to make things better.

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Sylvia Earle received her Ph.D. in phycology from Duke University. She is currently National Geographic’s Rosemary and Roger Enrico Chair for Ocean Exploration, as well as founder of Mission Blue, SEAlliance and Deep Ocean Exploration and Research. She formerly served as Chief Scientist for the National Oceanic and Atmospheric Administration. Among her awards are the TED Prize, the National Women’s Hall of Fame, and the inaugural Lifetime Achievement Award from the Seattle Aquarium. She is the author of several books, the most recent of which is National Geographic Ocean: A Global Odyssey.

• Mission Blue
• National Geographic profile page
• National Women’s Hall of Fame
• Wikipedia
• IMDb page
• Amazon author page
• Twitter

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