There were once pigs that lived in a really grassy enviornment. The pigs had variation within them, some of them were a tan color, and the other was a purple color.
The pigs didn't live in a safe enviornment though. Sometimes a wolfman would come through and eat some of the pigs. The pigs that were tan could hide easily from the wolfman because they could hide in the tan grass but the pigs that were purple were easily seen.
I can see you!
Soon the enviornment became almost all tan pigs and almost no purple pigs.
But soon it became winter time and all the grass disappeared. One special thing about this enviornment was that the sky would turn purple whenever winter came so this time when the wolf came back the purple pigs would be able to hide easier than the tan pigs.
So when the wolfman did come back the purple pigs were able to hide easily but the tan pigs couldn't find a good hiding spot.
Thus, all the purple pigs would be able to survive easier than the tan pigs during the winter, but when summer came again all the tan pigs would survive easier than the purple and the cycle would continue over and over again. The end.
Yeah celbrate now before summer comes again and we're all food again.