Podcasts > Stuff You Should Know > Selects: Slime Mold: 0% Mold, 100% Amazing

Selects: Slime Mold: 0% Mold, 100% Amazing

By iHeartPodcasts

In this episode of Stuff You Should Know, the hosts explore the fascinating world of slime molds, organisms that defy traditional biological classification. Though they were once thought to be fungi, these ancient life forms belong to the kingdom Protista and can exist as both single cells and large masses. Despite lacking a nervous system, slime molds demonstrate remarkable capabilities, including solving mazes, finding efficient paths to food, and sharing information between colonies.

The episode also examines how researchers are applying slime mold behavior to modern challenges. Studies have shown that these organisms can recreate efficient transportation networks, with patterns matching existing systems like the Tokyo railway. Their problem-solving abilities have applications in urban planning, and the tech sector is investigating how to use slime mold behavior patterns in artificial intelligence development and complex systems modeling.

Listen to the original

Selects: Slime Mold: 0% Mold, 100% Amazing

This is a preview of the Shortform summary of the Sep 20, 2025 episode of the Stuff You Should Know

Sign up for Shortform to access the whole episode summary along with additional materials like counterarguments and context.

Selects: Slime Mold: 0% Mold, 100% Amazing

1-Page Summary

The Biology and Classification of Slime Mold

Slime molds challenge traditional biological classification systems, as they exhibit characteristics spanning multiple kingdoms. Originally classified as fungi, they are now recognized as members of the kingdom Protista, representing some of Earth's most ancient life forms. These organisms can exist either as single cells or as large cytoplasmic masses, reaching sizes comparable to a medium pizza while maintaining a single cellular structure with multiple nuclei.

The Intelligent and Adaptive Behaviors of Slime Mold

Despite lacking a nervous system, slime molds display remarkable intelligence. Dr. Toshiyuki Nakagaki's research revealed their ability to solve mazes and find efficient paths to food sources. These organisms can even share learned information between colonies and demonstrate collective decision-making through chemical signaling. The slime mold Dictyostellium discoideum exhibits altruistic behavior, with some cells sacrificing themselves to form structures that help disperse spores, ensuring species survival.

The Potential Applications of Slime Mold Research

Researchers have found fascinating applications for slime mold behavior in modern problem-solving. At Hokkaido University, Atsushi Taro demonstrated that slime molds can recreate efficient transportation networks, developing patterns that mirror existing systems like the Tokyo railway. These organisms have even helped map ancient Roman roads, suggesting potential applications in urban planning. The tech community is now exploring ways to reverse-engineer slime mold behavior for AI development and complex systems modeling, highlighting the potential for nature-inspired solutions to modern challenges.

1-Page Summary

Additional Materials

Clarifications

  • Slime molds challenge traditional biological classification systems due to characteristics that overlap multiple kingdoms. Initially classified as fungi, they are now recognized as members of the kingdom Protista. This reclassification reflects their unique biological features that do not neatly fit into a single kingdom. Slime molds' diverse traits make them a fascinating subject for studying evolutionary relationships and biological diversity.
  • Slime molds can exist in two main forms: as individual single cells or as large, multinucleated structures known as plasmodia. In the plasmodial form, multiple nuclei coexist within a shared cytoplasmic mass, allowing the organism to function as a single entity despite lacking a traditional multicellular structure. This unique characteristic enables slime molds to grow and move efficiently, exhibiting complex behaviors and adaptations without the need for specialized organs or tissues.
  • Slime molds exhibit intelligence through complex behaviors like maze-solving and efficient pathfinding without a traditional nervous system. Research has shown that these organisms can share information, make collective decisions, and even display altruistic behavior, all without neural structures typical of intelligent organisms. Their ability to adapt and respond to environmental stimuli showcases a unique form of intelligence that challenges conventional definitions.
  • Slime molds, despite lacking a nervous system, have shown the ability to navigate mazes and find efficient paths to food sources through a process called chemotaxis, where they move in response to chemical gradients. This behavior is a result of their unique biological mechanisms that allow them to adapt and respond to their environment effectively. Researchers have studied this phenomenon to understand how these organisms exhibit complex problem-solving abilities without a central brain or nervous system. The findings have implications for fields like artificial intelligence and optimization algorithms, showcasing nature's innovative solutions to challenges.
  • Slime molds can communicate and share information through chemical signals. This allows them to pass on knowledge about navigating mazes or finding food sources. Through this chemical signaling, slime mold colonies can collectively make decisions based on shared information. This behavior showcases a form of distributed intelligence among slime mold communities.
  • Slime molds exhibit collective decision-making through chemical signaling, where they communicate using molecules to coordinate group behaviors. This process allows them to work together efficiently towards common goals, such as finding food sources or forming structures for reproduction. Through this chemical communication, slime molds can synchronize their actions and optimize their responses to environmental challenges. This mechanism showcases the remarkable adaptability and intelligence of these organisms in navigating their surroundings.
  • Dictyostelium discoideum, a type of slime mold, exhibits altruistic behavior where some cells sacrifice themselves to form structures that aid in spore dispersal, ensuring the survival of the species. This behavior involves a cooperative effort among the cells, with some individuals giving up their own chance of reproduction for the benefit of the entire colony. Altruism in Dictyostelium discoideum is a fascinating example of selfless behavior in nature, where certain cells prioritize the collective success of the group over their individual survival. This altruistic behavior contributes to the overall fitness and reproductive success of the slime mold species.
  • Slime mold research has practical applications in modern problem-solving, such as recreating efficient transportation networks and mapping ancient road systems. These organisms can inspire solutions for urban planning and complex systems modeling. Researchers are exploring ways to use slime mold behavior for AI development, showcasing the potential for nature-inspired problem-solving approaches.
  • Slime mold behavior is being studied for AI development and complex systems modeling due to its ability to solve problems efficiently and adapt to changing environments. By understanding how slime molds make decisions collectively and navigate their surroundings without a central nervous system, researchers aim to apply these principles to artificial intelligence algorithms. This research could lead to innovative approaches in creating AI systems that can adapt and solve complex problems inspired by the decentralized and adaptive nature of slime molds.

Counterarguments

  • While slime molds are recognized for their intelligence, it's important to clarify that their "intelligence" is fundamentally different from that of animals with nervous systems; it's more about adaptive behavior than conscious thought.
  • The classification of slime molds in the kingdom Protista is still a matter of scientific debate, with some arguing for further refinement within the classification system.
  • The ability of slime molds to solve mazes and find efficient paths might not necessarily indicate intelligence but could be an inherent biological function that can be explained through simple chemical gradients and tropisms.
  • The sharing of learned information between colonies in slime molds could be overstated; what is observed might be more about chemical signaling and less about the transfer of learned knowledge as understood in higher organisms.
  • The altruistic behavior observed in Dictyostellium discoideum, while fascinating, might not be altruism in a deliberate sense but rather a programmed cell death that benefits the colony, which is a common phenomenon in many organisms.
  • The applications of slime mold behavior in modern problem-solving, such as urban planning and AI, are still largely theoretical and experimental; the practicality and efficiency of these applications in real-world scenarios remain to be proven.
  • The comparison of slime mold growth to transportation networks, while intriguing, may oversimplify the complex array of factors that human engineers consider when designing infrastructure.
  • The use of slime molds in mapping ancient Roman roads is a novel approach, but it should be complemented with traditional archaeological and historical methods to ensure accuracy.
  • The enthusiasm for using slime mold behavior in AI development and complex systems modeling should be tempered with caution, as biological systems do not always translate directly to technological applications.

Get access to the context and additional materials

So you can understand the full picture and form your own opinion.
Get access for free
Selects: Slime Mold: 0% Mold, 100% Amazing

The Biology and Classification of Slime Mold

Understanding slime molds requires rethinking traditional categories, as these organisms bridge characteristics across different kingdoms.

Slime Molds, Once Fungi, now Protists

Slime molds present a biological classification conundrum, having traits likened to fungi, animals, and neither. Once considered members of the kingdom Fungi, slime molds are reclassified into the kingdom Protista, according to the present biological consensus. Even though mycologists, who traditionally studied fungi, continue their research on slime molds, these organisms are identified as some of the most ancient life forms.

Slime Molds Form a Distinct Kingdom With Fungal and Animal-Like Traits, Not Fitting Animals, Fungi, or Plants

The confusion regarding slime mold classification stems from their spore-producing nature and their congregation into large clumps that mirror fungal appearances. However, these seemingly fungal attributes fall short of defining them. It's clarified that slime molds are neither animals nor fungi and should be understood within their distinct category—a testament to their deep evolutionary roots.

Slime Molds: Single-Celled (Cellular) or Large Cytoplasmic Mass (Plasmodial)

The range of slime mold configurations include both single-celled organisms and expansive, wall-less cellular masses.

Slime Molds Can Reach Medium Pizza Size As a Single Cell Without Walls

These plasmodial slime molds can grow impressively large, equivalent to the size of a medium pizza. Yet, despite their size, they maintain themselves as a single cellular structure containing millions of nuclei and organelles without individual cell walls. This structure enables dynamic and coordinated movements towards nutrients by oscillating in response to their environment, resembling a single sheet of living tissue.

Cellular Slime Molds Are Single-Celled Organisms Forming a Swarm-Like Pseudoplasmodium

Al ...

Here’s what you’ll find in our full summary

Registered users get access to the Full Podcast Summary and Additional Materials. It’s easy and free!
Start your free trial today

The Biology and Classification of Slime Mold

Additional Materials

Actionables

  • Explore your local ecosystem by searching for slime molds during a nature walk, noting their colors, shapes, and sizes to appreciate biodiversity. As you walk through forests or grassy areas, especially after rain, look for the various forms of slime molds mentioned. Document your findings with photographs and compare them to online resources to learn more about their unique characteristics and their role in the ecosystem.
  • Create a simple terrarium to observe slime mold growth and behavior in a controlled environment. Use a clear container, moist soil, and decaying plant matter to mimic their natural habitat. Introduce a small piece of slime mold from a local source and watch how it grows and moves over time, providing a hands-on understanding of their dynamic nature.
  • Use the concept of sli ...

Get access to the context and additional materials

So you can understand the full picture and form your own opinion.
Get access for free
Selects: Slime Mold: 0% Mold, 100% Amazing

The Intelligent and Adaptive Behaviors of Slime Mold

Slime mold, a simple organism devoid of a nervous system, exhibits a range of behaviors that suggest a form of intelligence and the capability for adaptive decision-making usually attributed to more complex life forms.

Slime Molds Show Intelligent Behavior Without a Nervous System

Japanese researchers, including Dr. Toshiyuki Nakagaki, discovered that slime molds, such as Physarum polycephalum, can move in deliberate ways, spread out strategically, and even solve mazes to find food.

Slime Molds Navigate Mazes, Find Routes, and "Learn" to Share Information

In a notable experiment, Dr. Toshiyuki Nakagaki observed how slime mold managed to find the most efficient path through a maze to reach its food. The slime molds displayed the ability to learn and navigate around a bridge with a noxious substance, and once accustomed, they could transfer this knowledge to naive, unexposed slime molds, indicating a form of information sharing.

Slime Molds Search For Food, Then Unite and Move Toward the Best Sources, Showing Emergent, Decentralized Decision-Making

As Josh Clark describes, slime molds search for food by creating fan-like formations that move fractally toward food sources through a process of contraction and expansion. They exhibit a decentralized form of decision-making where cells closest to food emit cyclic AMP signals, prompting a collective movement toward the food without needing a leader or central cont ...

Here’s what you’ll find in our full summary

Registered users get access to the Full Podcast Summary and Additional Materials. It’s easy and free!
Start your free trial today

The Intelligent and Adaptive Behaviors of Slime Mold

Additional Materials

Clarifications

  • Physarum polycephalum, also known as "the blob," is an acellular slime mold with diverse cellular forms and a broad geographic distribution. It is a model organism for studying motility, cellular differentiation, chemotaxis, cellular compatibility, and the cell cycle. The organism goes through different stages in its life cycle, including a plasmodial stage where it forms a multinucleate coenocyte. Physarum polycephalum is commonly cultivated in research settings for its unique characteristics and behaviors.
  • Dr. Toshiyuki Nakagaki is a Japanese researcher known for his work on slime molds, particularly Physarum polycephalum. He has conducted experiments demonstrating the intelligent behavior and problem-solving abilities of slime molds, showcasing their unique capabilities in navigation and decision-making. Nakagaki's research has shed light on how these simple organisms can exhibit complex behaviors without a traditional nervous system, challenging conventional notions of intelligence in living organisms. His work has contributed significantly to the understanding of emergent behaviors and decentralized decision-making in biological systems.
  • Fractally means exhibiting a pattern that repeats itself at different scales within a system, showing self-similarity across various levels of magnification. This term describes how the structure of certain formations, like the fan-like formations created by slime molds, display intricate details that are replicated at smaller and smaller levels of observation. The concept of fractally helps to understand how complex patterns emerge in natural systems, showcasing a recursive and self-repeating nature in their organization.
  • Contraction and expansion in slime molds relate to their movement patterns. Slime molds contract and expand rhythmically to propel themselves towards food sources. This process helps them efficiently navigate their environment and locate nutrients for survival.
  • Cyclic AMP (cAMP) signals are a type of cellular communication mechanism used by organisms like slime molds to coordinate behaviors. These signals help cells communicate ...

Counterarguments

  • The interpretation of slime mold behavior as "intelligent" might anthropomorphize a biological process that can be explained through simple chemical signaling and adaptive responses.
  • The term "learning" when applied to slime molds could be misleading, as it implies a cognitive process; what is observed might be better described as a physiological adaptation to stimuli.
  • The concept of "information sharing" among slime molds could be an overstatement of what is essentially a chemical signaling process that leads to changes in behavior, not a transfer of knowledge as understood in cognitive beings.
  • Describing slime mold behavior as "altruistic" might be an anthropocentric projection, as the behavior could be driven purely by genetic programming that favors the survival of the species rather than a conscious sacrifice for the collective good.
  • The use of the term "decision-making" in the context of slime molds could be considered a misnomer, as it typically implies a cognitive process, whereas slime molds operate based on pre-programmed biological mechanisms.
  • The assertion that slime molds exhib ...

Get access to the context and additional materials

So you can understand the full picture and form your own opinion.
Get access for free
Selects: Slime Mold: 0% Mold, 100% Amazing

The Potential Applications of Slime Mold Research

In the realm of scientific inquiry, researchers are finding that the humble slime mold may hold solutions to some of the most complex and modern problems in urban planning and technology.

Algorithms From Slime Mold Movement Can Optimize Complex Systems Like Transportation Networks

Recent studies have shown that the movement and growth patterns of slime molds can guide the optimization of transportation and other networks.

Slime Molds Recreate Roman Roads and Tokyo Subways, Showing Potential for Urban Planning

Researchers have utilized slime molds to recreate ancient and modern transportation systems. In one experiment, Atsushi Taro from Hokkaido University placed oat flakes, representing Tokyo neighborhoods, in a petri dish and observed slime molds growing networks between these oat flakes. Remarkably, the patterns closely resembled the Tokyo railway commuter system, which exemplifies the mold's ability to naturally develop efficient pathways. This holds the promise of utilizing slime mold behavior as a blueprint for optimizing urban designs.

Similarly, in experiments signifying ancient Roman cities, slime molds (fisarium) mimicked the layouts of long-forgotten Roman roads, uncovering lost routes and affirming known ones. Clarke and Bryant have humorously posited that someday every city planner might rely on a slime mold researcher for infrastructural guidance.

Slime Mold Algorithms Model Universe's Invisible Structure

Reverse-Engineering Slime Mold Behaviors Yields Simulations Mimicking Growth Patterns ...

Here’s what you’ll find in our full summary

Registered users get access to the Full Podcast Summary and Additional Materials. It’s easy and free!
Start your free trial today

The Potential Applications of Slime Mold Research

Additional Materials

Clarifications

  • Slime molds are single-celled organisms known for their ability to efficiently find optimal pathways when foraging for food. Researchers study their behavior to develop algorithms that can be applied to optimize complex systems like transportation networks, mimicking the natural efficiency of slime mold growth patterns. By observing how slime molds create efficient networks between food sources, researchers can adapt these principles to improve the flow and organization of transportation systems, potentially leading to more effective urban planning and infrastructure design. This approach leverages the innate problem-solving abilities of slime molds to inform and enhance human-made systems.
  • Slime molds can recreate ancient and modern transportation systems through their unique ability to grow and connect different points in a manner that mirrors the efficiency of real-world networks. Researchers set up experiments where slime molds are presented with stimuli representing urban layouts or transportation networks, and the molds naturally form pathways between these points, resembling the structure of actual road or subway systems. By observing and studying how slime molds create these networks, researchers can gain insights into optimizing urban planning and transportation design based on natural principles.
  • Reverse-engineering slime mold behaviors for AI and complex system ...

Counterarguments

  • While slime molds have shown potential in modeling efficient networks, their application to real-world urban planning may be limited by the complexity and scale of human infrastructure and societal needs.
  • The optimization of transportation networks using slime mold algorithms may not account for unpredictable variables such as economic factors, political decisions, and human behavior.
  • The recreation of transportation systems like Roman roads and Tokyo subways by slime molds is a simplified representation and may not be directly transferable to the planning of modern, multifaceted urban environments.
  • The assumption that slime mold behavior can be directly translated into efficient urban planning does not consider the necessity of a multi-disciplinary approach that includes social, environmental, and economic considerations.
  • Reverse-engineering slime mold behavior for AI and complex systems modeling may not capture the full range of human decision-making proce ...

Get access to the context and additional materials

So you can understand the full picture and form your own opinion.
Get access for free

Create Summaries for anything on the web

Download the Shortform Chrome extension for your browser

Shortform Extension CTA