Michael Levin on Biology's Deep Questions: From Planarian Immortality to Xenobots and the Nature of Self

Michael Levin, a leading biologist from Tufts University, delves into the profound mysteries of life, evolution, and consciousness, drawing insights from diverse biological systems. The discussion begins with the remarkable planarian worm, highlighting its immortality and ability to regenerate a brain that retains memories even after decapitation, challenging conventional thermodynamic theories of aging. This introduces the core idea that biological systems possess inherent plasticity and computational capabilities far beyond what is typically attributed to genetic blueprints. A central theme is embryogenesis, the process by which a single cell develops into a complex organism with high-level cognition. Levin argues that this transformation from "just physics" to "mind" is a smooth, gradual continuum, not a sudden event. He posits that DNA primarily encodes the "hardware" of life—proteins, ion channels, and signaling factors—while the "software" of development and function is governed by generic laws of mathematics, computation, and physics. Evolution, in this view, discovers these pre-existing laws, rather than building them from scratch, allowing for emergent properties like logic functions from simple biological components. Levin's groundbreaking work with "xenobots" exemplifies these principles. By taking frog skin cells and removing them from their normal embryonic context, his lab observed these cells self-assembling into novel proto-organisms with unexpected capacities, including navigation, complex behaviors, and kinematic self-replication. This "engineering by subtraction" reveals that cells possess default, higher-level agendas that are normally suppressed by their environment. This leads to the concept of "agential materials," where biological substrates are not passive but have their own goals, preferences, and memories, necessitating a collaborative approach in bioengineering, akin to training an animal rather than micromanaging every neuron. The conversation extends to the nature of intelligence and the "self." Levin argues against the notion of a central dictator in biological systems, emphasizing that all intelligence, including human cognition, is a form of collective intelligence—a "bag of neurons." He challenges the idea of a discrete point where cognitive powers emerge, suggesting a continuous spectrum from single cells to complex organisms. Examples like salamander limb regeneration, which stops precisely when a correct limb is formed, illustrate biology's top-down, goal-directed control mechanisms. This perspective encourages applying concepts from cognitive neuroscience to understand how biological systems maintain morphological homeostasis and how the "self" originates and unifies from distributed components, even questioning the fixed number of "selves" within an early embryo.

"it turns out that if you train a planarian and then cut their heads off the tail will regenerate a brand new brain that still remembers the original information"

"planaria are Immortal so they do not age there's no such thing as an old planarian so that right there tells you that these theories of thermodynamic limitations of on lifespan are wrong"

"what embryogenesis tells us is that that transformation from physics to mind is gradual it's smooth there is no special place where you know a lightning bolt says boom now you've gone from from physics to True cognition"

"what DNA encodes is the hardware of Life DNA contains the instructions for the kind of micro level Hardware that every cell gets to play with... The rest of it is in so-called generic laws and these are laws of mathematics these are laws of computation these are laws of um of physics"

"if you evolve an ion Channel which is Ion channels are basically transistors... you immediately get to use things like truth tables you get logic functions you don't have to evolve the logic function you don't have to evolve a truth table doesn't have to be in the DNA it's you get it for free"

"what we have done there is engineer by subtraction which you've done is you've removed the other cells that normally basically bully these cells into being skin cells and you find out that what they really want to do is is to be this they want their default behaviors to be a xenobot"

"these are agential materials this is your you're now collaborating with your substrate because your material has an agenda These cells have you know billions of years of evolution they have goals they have preferences they're not just going to sit where you put them"

"you have a salamander it's got an arm you can you can amputate that arm anywhere along the length it will grow exactly what's needed and then it stops... it stops when a correct salamander arm has been completed"

"we are all made of parts and so if if you believe that... that we in fact have a centralized um set of goals and preferences and we plan and we do things and so on you are already committed to the fact that a collection of cells is able to do this because we are a collection of cells"

"no one has to my knowledge no one has come up with any convincing discreet Step At which my cognitive Powers disappear right it just doesn't the biology doesn't offer any specific step it's com it's incredibly smooth and slow and continuous"