[No system + plot flow + few abilities]
The colonial civilization discovered the Earth, a planet where life had just been born, and injected "water drops" into the Earth at the right time to stimulate biological evolution, catalyze life on the Earth, and intend to turn the Earth into their breeding ground.
The emergence of human beings was not within their expectations. The catalyst that could not be prepared was completely inconsistent with human physique. Under the stimulation of "water droplets", creatures called zombies were born.
Without the system, without the help of aliens, and without human beings even having a body capable of completing evolution, people can only fight against the outside world with their flesh and blood.