does not mean there are no* powerful cultural forces that inhibits us to kill other humans — there are: such as the Ten Commandments. Among other codes.
Those codes must be taught, by example.
Master to student.
Grandfather to grandson.
Where those codes are not taught, terror reigns.
Your logic, once again, fails.
Perhaps if you talk to your grandparent, or an uncle, he can explain it to you.
/johnny