There were two ways for a human to evolve.
One was to receive a piece of essence from a higher-ranked species of another race, which would transform them into a part of that race.
Many people debated whether this process truly counted as "evolution" or if it was merely being forcibly evolved, especially since it involved becoming part of another race.
However, this concern only applied if the transformation was complete.
When a human was turned into another race, they would not become that race entirely.
They would still retain a part of their original human genetics.
For example, when an alpha werewolf bit a human, the human would evolve into a beta werewolf.
However, they would not be considered a true werewolf because part of their human genetic code remained within them.
During this transformation, a small portion of the alpha's essence would be transferred into the human's inner system through the bite.