The question being one of necessity, we must answer the question, "necessary for what?" The most common use of this word refers to survival and/or success, so from this perspective, I see two relevant points:

• Government did not exist during most of man's evolution, so it cannot be necessary, since we survived (succeeded in continuing to exist).

• Government represents external authority upheld by violent coercion, and is therefore immoral (i.e. evil); thus, if necessary, it would mean evil is necessary for humanity to survive and thrive. This cannot be, since morality is the cause-and-effect of human behavior, whereby immorality is a cause that necessarily yields entropic, degenerative effects.

So, no, government cannot be necessary.