Genotype vs. phenotype.
Genotype is the genetic make up of the animal.
Phenotype is determined by how the environment affects the animal.
Jagdtank gives a perfect example of this. The litter of pigs all had practically the same genes thus genotypically they are the same, but since they were raised in different environments they were phenotypically different.
For a population to develop "new" genetics without selective breeding takes many (possibly 100's) generations, but for a phenotypical change may only take one generation.
Genotype and phenotype IMO are both related to the environment when we are talking about wild animals...we are talking about hogs in the wild...I can see that it would not take too many generations to change the pigs because of all the pressure that is put on them from hunters with guns and doggers...the doggers will catch the slower hogs and the ones that want to stop and fight...The smarter ones and faster ones that want to run and those that run to the thickest part of the terrain live to breed and run another day...so phenotypically they have to change as well so they can run and fight and just be a more agile type of hog...Genetics is selective as well...
Jagdtank did say that those rooters had some feral blood in them so they are not identical to the other domestic hogs...
evolution sometimes takes hundreds and thousands of years but in some cases not that long...those that can adapt survive...those that can't will become extinct...
