The large (Quinn Dog Millionaires) live in space and fly onto other planets for sanctuary. The Millionaires are killed and eaten by Diablitos. The Diablitos have spaceships which make them more advanced.
More smaller millionaires are born in space but there are too many for the area they live in. The food in which they eat has diminished to very little due to their size.
Not all the Millionaires are the same. Some are brown or black. Some are strong and some are fast. The black ones survive better than the light colored counterparts due to the fact that they blend in with the space all around. Also being strong also has its advantages over the fast nimble millionaires.
The light colored nimble millionaires get eaten more than the darker stronger ones. This makes them easier to spot from the spaceships and the diblitos don't have to waste their time.
Dark colored millionaires have a better chance of survival because they camoflauge themselves with the dark colored space.
Only the dark millionaires get to survive so when it's time to mate most of them turn darker instead of black. Therfore a greater amount of millionaires are dark in the next generation.