In 25 words of less?
Re. 'HistMat', what Engels called 'materialist conception of history' asserts that consciousness is conditioned by most fundamental of human tasks: struggle for material existence. In Marx's view, ideas, beliefs, and theories are formed through interaction between humans and material/economic circumstances out of which they emerge. Whether or not 'HistMat' will be necessary in a future society not marked by internal contradictions/antagonisms may be an interesting question to some folks but so is question about origin of the family for some people. As Kathleen Gough wrote some years ago about the latter: trouble is no one really knows.
> I guess I have a hard time imagining some clean break between
> capitalism and post-capitalism, in which all issues of power and
> exploitation disappear and humanity becomes one big happy family.
> Doug
Apparently so did Marx, recall that transitory 'socialist' period that would last as long as class antagonisms persisted. But at the risk of being disparaged as a utopian, without a vision of what could be, theory is overwhelmed by what is and loses its critical edge.
We're a happy family/We're a happy family/We're a happy family/Me, Mom & Dad (Ramones) Michael Hoover