Ack. That last line should be: “If your head DOES NOT come pre-equipped with ….”. Sorry.
^^^^^^^ CB: Individual humans do have pre-equipped or genetically inherited brain structures that are unique in ability to use symbols, culture and language. ( symboling is representing something with what it is not for purposes of communication to other humans ) The content of individual human ideas and language is accumulated over many generations and passed on to succeeding generations. So, most ideas an individual human has today come from the experience of many , many other humans, living and dead. They are socially derived not derived from inside the individual's brain. The individual's brain is mainly a very agile nodal point connnected to millions of other humans, a social processing center. The human Individual is a social Individual. Also, ideas exist as systems of ideas, like grammars, religions. Individuals don't just learn "single" ideas from society ( other people dead and alive), but systems of interrelated ideas , both logically consistent and contradictory. They learn systems of rules, bundles of custom, habit, moral codes, grammars , vocabularies with semantically interconnected lexical items. Marx called religion an "encyclopedic compendium" of ideas. In general, peoples behavior ,conduct , activities are governed by these systems of rules and ideas, though , of course , "rules are made to be broken" and are a lot; but they are followed a la mode. Individuals are socially determined by internalizing these systems of ideas and rules.
Socially determined _is_ objectively determined. The subjectivity of the individual is overwhelmingly objectively determined by her _social_ objective surroundings. Materialism is belief in the existence of objective reality, and the determination of individual subjectivity by that objective reality. So, social determinism of the individual subjectivity is objective determinism , and it is materialism.
Furthermore, historical materialism holds that ultimately, at revolutionary transformations of society , the change in relations of production (base) changes "super-structure" or laws of property, and other systems of ideas. The base determinism occurs at revolutions.
In non-revolutionary times, which is most of the time of history, there is more recipricol determinism between base and superstructure. Politics and the state determine that the base structure doesn't change, prevents reform and revolution, etc. That's what the following famous passage from Marx is about.
"It is not the consciousness of men that determines their existence, but their social existence that determines their consciousness."
In the social production of their existence, men inevitably enter into
definite relations, which are independent of their will, namely
relations of production appropriate to a given stage in the
development of their material forces of production. The totality of
these relations of production constitutes the economic structure of
society, the real foundation, on which arises a legal and political
superstructure and to which correspond definite forms of social
consciousness. The mode of production of material life conditions the
general process of social, political and intellectual life. It is not
the consciousness of men that determines their existence, but their
social existence that determines their consciousness. At a certain
stage of development, the material productive forces of society come
into conflict with the existing relations of production or – this
merely expresses the same thing in legal terms – with the property
relations within the framework of which they have operated hitherto.
>From forms of development of the productive forces these relations
turn into their fetters. Then begins an era of social revolution. The changes in the economic foundation lead sooner or later to the transformation of the whole immense superstructure.