Mental Model: Fitness Landscapes

Fitness Landscapes are used to visualize the relationship between genetic makeup (genotype) and evolutionary fitness (the ability to survive and reproduce). A fitness landscape is a vast landscape divided into a grid of billions of squares. Each square represents a genotype—some squares represent birds; some fish; some humans; with the majority being all the variations of genetic possibility that couldn’t survive in reality. Each square is very similar to its neighbors: two of the same species with a small variation, or two different but related species. The closer the squares, the more similar the genotype, and the further the squares, the more different. The fitness of each genotype is represented by its height on the landscape. Valleys represent low fitness, mountain peaks high fitness.

Fitness Landscape

Over time, species tend to move up the landscape to the nearest peak (A), where all future paths of variation lead downward. The peak that a genotype “settles” on is most likely to be a local optimum, which is not necessarily the highest peak in the landscape (a global optimum). This is because selection pushes fitness towards nearby peaks (what is called a basis of attraction), but lacks the foresight to select the highest peak.

To get to a higher peak, a species may have to reduce its fitness in the near term (C) as it slowly traverses across a valley in order to improve fitness in the long term. In order to make this shift, there has to be sufficient instability or challenge; otherwise, an organism will not opt to leave the intermediate peak and suffer the unknown prospects of the valley. If the valley is too low or the higher peak too far away, it may be unreachable as the low fitness hurdle can’t be overcome. (An example is the lack of wheeled animals, which although beneficial is inaccessible due to the valley of low fitness genotypes around it.)

Evolution usually moves in small steps, but occasionally it takes wild leaps—a single mutation might give a creature an extra pair of legs or another radically different feature. Most of the time these leaps result in much lower fitness (B), and therefore don’t last. But other times it allows the genotype to jump to a higher peak without the slow process of going down before going up.

Every landscape has different terrain that can be on a scale from flat to rugged. A rugged or coarse landscape has many local peaks and deep valleys, while a flat landscape has only very small hills (all genotypes have about the same success rates).

Landscapes don’t remain static—they shift over time due to either environmental changes or adjustments as organisms move across it. The movement can vary from being stable (relatively flat and slow to change) to roiling (likely rugged and changing quickly). Given the likelihood of ever-shifting landscapes, the evolutionary mix of small steps and occasional wild leaps is the best possible way to adapt to the environment.

Generalists vs. Specialists (And the Specialist’s Dilemma)

In December of last year, I gave a presentation to a group of investors on the mental models of robustness and generalist/specialist species. Below are some of my findings, along with how these models can be applied to business and investing.

Animal species reside on a scale with “generalist” on one end and “specialist” on the other. Specialists can live only in a narrow range of conditions: diet, climate, camouflage, etc. Generalists are able to survive a wide variety of conditions and changes in the environment: food, climate, predators, etc.

Specialists thrive when conditions are just right. They fulfill a niche and are very effective at competing with other organisms. They have good mechanisms for coping with “known” risks. But when the specific conditions change, they are much more likely to go extinct. Generalists respond much better to changes/uncertainty. These species usually survive for very long periods because they deal with unanticipated risks better. They have very coarse behavior: eat any food available, survive in many climates, use a simple mechanism to defend a wide range of predators, etc. But unlike specialists they don’t maximize their current environment, because they don’t fill a niche where they could be more successful. It’s tough being a generalist—there’s more competition.

An environment with more competition breeds more specialists. Rainforests have huge diversity and competition, and therefore many specialist species.

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