The conscious subject is supposed to be the bedrock for conceiving human being for all time. Hence, for instance, science speaks unrestrainedly of the evolution over millennia of consciousness in the species of animal called homo sapiens. Humankind is thus conceived as just one among many animal species and given the flattering label of 'wise'. Such putative long-term ontogenetic evolution of consciousness is thought to be somehow a result of, or at least concomitant with, the enlargement of the human brain over long periods of linear time. Human consciousness is supposed to emerge in linear chronological time through some kind of increase in complexity of the brain's neural interconnections which, in turn, is explained (teleologically) as serving the enhanced survival of the species. Science's conviction is that one day 'we' will scientifically explain the evolutionary emergence of human consciousness on a scientifically materialist basis.
Conceiving human being itself as specifically distinguished from other animal species by intelligent consciousness residing in the conscious subject, however, shows how our self-conception is the plaything of our historical time's own mind, i.e. our shared historical time-mind or Zeit-Geist that here encompasses both the mind and spirit of the times. For, marking the human species with the specific difference of (intelligent, mooded) consciousness, as happened only in the modern age, differs radically from ancient determinations of this hallmark as soul, anima, animus, ψυχή or νοῦς. Talk of the soul, for instance, is out of bounds for today's science. The Christian soul is also conceived in an essentially different way from the Latin anima or the Greek ψυχή.
One consequence of conceiving human being as subjective consciousness is that mind itself becomes individualized, encapsulated in individual, interior consciousness. Such postulated, brain-based, individual consciousnesses 'inside' can then only come together 'outside' through some sort of collectivity of consciousness which modern mainstream philosophy conceives as collective intentionality of will. What this inside/outside dichotomy actually means and how (since, on closer examination, it can be seen that it does not do justice to the phenomena themselves) it can be overcome (as treated in other of my posts and books) remains a hardly noticed ontological problem.
Such a conception of subjective consciousness comes too late, for individual consciousness always already partakes of the mind of our scientifically dominated historical age. The Zeit-Geist is prior to the conception of interior consciousness of individual subjects, for it is the source that has cast human being itself as interiorized consciousness. The casting of human being itself as individual subjectivity endowed with interior consciousness is itself a fairly recent historical event. This hermeneutic casting is not the terminus of history, since, through philosophical thinking, history may have a further twist through recasting. The casting itself can be historically interrogated and revised, thus rescuing human being conceived inappropriately as subjective consciousness from its status as mere plaything of an hegemonic mind-set by paying close attention to certain simple, elementary phenomena that are "hard to see" (Aristotle), i.e. are taken as self-evident and therefore, even after millennia of Western thinking, have yet to come to adequate concepts.
The crucial point in the present context is that the very interiority of consciousness vis-à-vis an objective external world supposedly independent of subjective, individualized consciousness is questionable. Such questioning is anything other than mere scepticism, but forceful interrogation of entrenched clichés in thinking that brings an alternative to light. Despite our age's hegemonic mind-set that is fixated on an absolute will to effective power over all kinds of movements (including even the explanatory power of evolutionary story-telling), the Zeit-Geist retains nevertheless an historical malleability under philosophical interrogation that can transcend such a fixation.
Further reading: A Question of Time: An alternative cast of mind.