It been 20 years since the yellow pigs have gone extinct, but now all the pigs are excepted all around the world. Most of the pigs have changed their life style and have became farmers...
They farm a mushroom that only grew in fields of their breeding grounds. The mushroom is used as a drug for the pigs it takes them back in time and shows them the evolution of the mushrooms.
Alfred Pig Wallace was a pigish biologist that had studied biology stuff and plants (mostly the magic mushroom of his people). He had used the mushroom to develop the theroy of natural selection.
Alfred explained his theroy to two other biologists Bobby Bobertine and Doug Hammercock. Booby told Alfred that he had discovered the same thing in his studies of the mushroom a noticed how the mushroom has changed over time because thats what the mushroom does.
Doug told them the mushroom didnt affect humans and was used in their gourmet foods. He wanted to do tests and experience what they had with the mushroom. They all agreed that they would do a brain transplant with a random pig person.