The more complex the world gets, the more we need models to simplify it. One of the models I return to often is fitness landscapes, which can help solve problems, design better experiences, and explain the world around us.
Imagine you and a group of friends are on a team playing a game.
The game takes place on a huge playing field with rough, mountainous terrain, like the Himalayas or Alps. The only goal is to increase your team’s average altitude. This seems easy enough, but there are a few catches: (1) any player can only see a few feet ahead of them, (2) the terrain slowly changes over time, and (3) if a player drops below a certain altitude for long enough, they’re eliminated. Given these rules, what strategies would your team use to find the highest peaks?
This is a metaphor for the “game” that species must play to survive in an ecosystem.
The terrain is a fitness landscape representing a library or design space of every possible variation of organism, spread out over a nearly infinite surface. The closer together on the surface, the more similar the genotype. This means single species would be clustered together. Dogs would be near wolves, far from fish, and even farther from fungi.
Altitude indicates the fitness of the organism — or how likely it is to survive in a particular environment. The higher it is on the landscape, the better the design and more fit the organism. Below a certain threshold, organisms can’t survive and species go extinct.
As a model, landscapes can help show us visually and mathematically how to find the best designs. The original concept was developed by evolutionary theorist Sewell Wright in 1931, and focused only on biological entities. But a design space could represent almost any set of possibilities — as long as it has building blocks or variables that combine into many variations, each with a value (or fitness level) that can be assigned. This means it could apply to design spaces of problems, equations, technologies, strategies, memes, or even sets of LEGOs.
Features of landscapes
A vast majority of the variations on a typical landscape are bad designs. These are oceans of low fitness, below the surface of which organisms are incapable of survival or reproduction.
But certain regions — springing out of the oceans like islands or continents — are full of a range of potential variations, all with some usable level of fitness. The basic features of these regions of terrain are:
- Local peaks or plateaus — A point or area of high fitness where all surrounding paths go down.
- Global peak — The highest peak in the region. The fittest entity in the area. The best design of all similar variations.
- Valleys — Flatter areas of low fitness adjacent to hills and mountain ranges.
- Pits or Crevasses — Deep holes of low fitness below the “sea-level” of survival.
Peaks are good. Pits are bad. And crossing valleys is very risky: you could find higher fitness, but likely not.
The unconscious process of evolution drives genotypes uphill over time, finding and settling on peaks of fitness until the landscape shifts or some other factor forces a move. More on this later.Continue reading “Lay of the Landscape”