The fact human skip them apart is crucial here. this is a commonly defined as "groups of interpreting natural populations that are reproductively isolated from other such groups."
cell reproduction is the process by which cells divide to form new cells. each time a cell divides it makes a copy of all its chromosomes, which are tightly coiled strands of DNA, the genetic material that holds the instructions for all life, and sends an identical copy to the new cell that is created.
The cerebral cortex of the brain has four paired lobes.
one of these four paired lobes is the frontal lobe and it occupies 2/3rds of the entire human brain.
the frontal lobe is associated with performing tasks such as speech and language production, walking and running, classifying and identifying objects, reacting to feelings, forming memories, forming the personality of a person, and attention involving tasks.
Since after the injury, Zack has an altered personality and his reaction to the situation has changed, this points out to the fact that he is most likely suffering from frontal lobe injury.