According to reincarnation beliefs, how does one work his way up as an animal?
For example a dog... how can a dog do anything really good or bad?
Or maybe like....an earthworm.
This is why the whole reincarnation beliefs are wacky. Animals are soulless,moral-less, and without understanding creatures. Animals can't sin. Animals are not even capable to know what they are doing is wrong.
People are reincarnated into people again.
charity work. thats why jews and muslims dont eat pigs and where the phrase "selifish pig" comes from,they dont do any charity work.
He becomes domesticated, then he can stay in the house.
The ancient Pythogorans believed that after your death you were granted the Gods wisdom to look at yourself and decided what your next life would be in order to help your soul learn the lessons it needed to learn. The idea that each life is a reward or punishment for the last one actually makes very little sense when you consider how many bad people have great lives, which is why modern Christians misrepresent reincarnation that way. Don't forget that until the 3rd century many Christian sects also believed in reincarnation, as have a lot of other faiths, the concept is too varied and complex to pick just one version and act as if that were the whole of it.
Good question, not so simple an answer...
In Buddhism, it is often emphasized that we have many, many rebirths. The bottom-line explanation is found in the idea of karma; when we do motivated positive actions, we create the causes for happiness and fortunate rebirths, when we do negative actions, we create the causes for misery in the future.
As an animal has a very limited amount of intellect and choice or motivation, it is unlikely that an animal can do much 'good' or 'bad' for the next rebirth. So it is likely that the actions (karma) done in a life before this life will determine where an animal will be reborn.
A simple example: if a dog has been a human in his previous life, then some negative actions during that human life may have caused him to be reborn as a dog. During a life as a dog, very limited good or bad actions can be done (with a clear motivation), so perhaps another positive or negative action done during his life as human will determine the next rebirth. If that is another negative action, perhaps the dog will again be reborn as animal, if the action of the past was very positive, he may have a chance for a human life again.
In this way, being reborn as an animal is considered quite negative, also because the animal has little control over his future suffering or happiness. At least as a human we can make conscious decisions that will affect our future.