Natural selection is the process by which an species of organism adapts to its environment over several generations. It is a cornerstone of Charles Darwin's theory of evolution. In the case of Norns and other Creatures, natural selection is similar to letting them breed on their own without any interaction or selective breeding. This mode of playing is commonly called a wolfling run.
The natural selection process is based on the principle of "survival of the fittest." For example:
- A population of Norns lives in a certain world. The vast majority of these Norns are from early generations with few mutations.
- An infectious disease attacks the Norn population. Most of the Norns die, but a very small number of them have a gene which allows them to survive it.
- The surviving Norns pass on the disease-resistance gene to their offspring.
- The next generation will have a far higher percentage of Norns which are resistant to the disease, and the next time it besets the population, more Norns will survive.
So, in this example, the Norns with the disease-survival gene were the "fittest", and thus survived to reproduce. Meanwhile, those who did not possess this gene perished, preventing this lack of resistance from continuing in the population.
These mutations which are passed on slowly change the population over time. Generally, only mutations which are beneficial exist for any siginificant time in the population; bad mutations are eliminated by the same process outlined above. Mutations which help an organism in its environment are called "adaptations", and are developed over several generations.