Tragedy of the Common Mold

Slime molds are a class of simple microorganisms with a surprising amount of intelligence given their lack of brain. Famously, they are excellent at optimizing transport networks, and they also showcase rudimentary memory and communication abilities.

Unknown slime mold I found on a log

They also have learned how to prevent social collapse. They avoid falling into the trap of the “tragedy of the commons”: where everyone's individual gain depletes a shared resource, harming all.

Let's look at how slime mold reproduction works (we'll talk about "aggregation" based reproduction; there are many different slime molds with different strategies). 

When food gets scarce, individual slime mold cells cluster together to form a structure called a fruiting body. This structure has two parts: a stalk made of cells that die to support the structure, and reproductive spores at the top that will spread to create new colonies. 

Notably, the individual cells cooperating on this structure are not belonging to the same multicellular organism — nor are they necessarily even brothers or cousins. They are just opportunistic collaborators, and yet, some of the cells have to forgo their chance to reproduce and join the stalk, so that the fruiting body can form at all. 

Comatricha nigra fruiting bodies

Cheaters are cells that take special efforts to avoid becoming part of the sacrificial stalk. Instead, they weasel their way into the reproductive spores, taking advantage of the other cells' sacrifice without contributing to the group effort. 

When too many cells cheat, the whole reproductive system fails. Without enough cooperative cells to form the stalk, no cells can reproduce at all. This creates a hard limit on how much cheating the system can handle, and unsurprisingly the slime mold populations have controlled levels of cheaters. There are genetic safeguards to make it hard for cheaters to evolve and succeed, and on the unlikely occasions when cheaters succeed in taking over the population, of course the collapse causes a failure to reproduce. The result is that not many cheaters exist, and this doesn't form a huge problem for slime molds.

This is a prime example of how organisms solve the tragedy of the commons, even in this most basic and simplistic species. Natural selection has pushed life to find a sweet spot between competition and cooperation. They need to compete enough to thrive, but cooperate enough to keep their shared systems working.

This balance shapes human societies too. Too many cheaters, or too much cheating by a few individuals, can make the whole system collapse.

The fact that our oldest and most basic ancestors in bacteria and slime molds, have these built-in protections against cheating might suggest humans have similar genetic patterns. And intuitively, it seems like we do have cultural norms and built-in intuitions to prevent cheaters from overrunning. Most of us are not cheaters after all!

But modern large-scale human society works very differently from the environments we evolved in and built our culture in. A slime mold cell, or a member of an ancient human tribe could only control so much of their group's resources, so it would take an overwhelming amount of cheaters to collapse to society. 

Today, a single cheater could wield immense power to cause an entire collapse themselves — controlling nuclear weapons that can destroy society at the press of a button, or heading power structures that enable them to commandeer for themselves the finite resource away from the rest of humanity in both the present and future. In a context where all it takes is one or two fluke cheaters to ruin everything, our biological safeguards that limit the population share of cheaters is not sufficient to prevent collapse.

Our biological evolution gave us tools and intuition for balancing competition and cooperation, but our society evolved much faster than our genes. The systems that work for slime molds might still teach us a basic and important lesson. If we want to carry on, we must find better ways to live that keep cooperation and competition in balance. We must ourselves design systems that limit the amount and potential power of cheaters.