What they say, including what Marx says in the preface to A Contribution to the Critique of Political Economy, is that the historical process is a process that substitutes rational self-determination for instinctive determination through "education" by means of "self-estrangement" within the labour process, a process defined by relations of production..
That "mind" - "self-conscious reason" - develops within these relations is evidenced by the development of "the productive forces of social labour" since these objectify this development.
It's for this reason that "the economic structure" is "basic" and other expressions of the development of mind - e.g. in politics, religion, philosophy, art - are "superstructural."
^^^^^^^^
CB: Your statement here doesn't say why evidence/expression of rational self-determination and self-conscious reason is "basic" in the economic structure, but not basic in superstructure.
I'm saying that the expression in economic structure is "basic" because
In human history and society , the necessary
> conditions are (in) material production. That's why Marx focuses on
> material production as a scientific, necessary or rational approach to
> human history.
like I said two posts ago.