One day, Phillip Buster had an idea. Not many people lived on the Earth yet, and his tribe relied on hunting and gathering to survive. Wolves were good at hunting, he mused. Wouldn't it be interesting to have them work for him?
He managed to get some wolves into possession and carefully put them together to have cubs. Neither Jeans nor genes were known at his time, but Phillip did know that children looked different from their parents and also exhibited different personalities. Maybe the wolves would eventually have an offspring that his tribe could use.
Genes are the blueprints of a being, how it is shaped, how it grows and in many ways even how it behaves. But these blueprints don't copy perfectly. There are small alterations, changes, and so a new animal would always be slightly different from the animals that came before. Perhaps it would have the tendency to be more playful, or it may be better at sniffing, or it may be friendlier towards other beings, such as Phillip himself.