Mathematical modeling of stem cells: A complexity primer for the stem-cell biologist

Many of us have been fascinated by the straight line of ants stretching from food sources to the anthills we found in our gardens. Taking a closer look, we found that this straight line was made from hundreds of individual, industrious ants, each behaving energetically. If we next focus on an individual ant’s behavior (from a modeling perspective, looking at the individual elements of a system is often called the micro view), it is very easy to interpret the behavior of the individual as unfocused and chaotic, and it is certainly very difficult to interpret its behavior as being purposeful when taken in isolation. It is only when we take a step back and look at the behavior of the entire group (called the macro view) that we can observe a purposeful global system of behavior. This purpose, bringing food back to the anthill, emerges from the total of the individual behaviors and interactions of the apparently undirected individual. Somehow, the sum of the local interactions of each individual—responding only to their local environment—produces a stable, surviving system, even though individual ants get lost or die.