The Founder Effect

For hundreds of millennia, the African ancestors of today's domestic cats were almost uniformly shorthaired, striped tabbies.

Yet after only a few millennia jf migration out of Africa, hundreds jf coat colors, patterns, and lengths exist.

In the large population of cats in North Africa, any random gene mutation had little chance of spreading widely unless it offered a substantial adventage to the cat.

Most genetic mutation simply vanished within a few generations. In an isolated feline population, mutations have more chance of surviving.

The orange-and-white cats of Scandinavia or the polydactyls of Boston and Halifax are both mutations from the genetic "norm." When these cats were taken to regions with few or no cats, they represented a large percentage of a small gene pool.

The long-term genetic influence of early members of a cat population is called the "founder effect." The founders have a potent influence on a new population.

This is why certain patterns or colors are prevalent   in some countries; it is also the basis for the development of new breeds. This leads to the question of just what makes a breed.

From a purely genetic perspective, there is no such thing, because the potential genetic differences within a breed, particularly those with large numbers, outweigh the average genetic differences between two different breeds.

For example, the DNA profiles of two Siamese can differ far more than those of a Siamese and a Persian. The definition of a breed is decided on a few obvious effects, such as coat color or length and body type: from a genetic perspective, these differences are slight.