This strikes me as being closer to Heidegger's conception of fallen-ness than Marx's of alienation. The latter really is a condition of capitalist societies, not to be confused with the ever present human condition of work, or opposition to nature.
Mankind will always be somewhat estranged from nature. Even under Comunism, should that ever come to pass, people will get ill and die, and roast chickens will not fly into our mouths. The alienation of man from man in the generalised exchange of comodities, however, is a specific feature of capitalist societies. Alienation is not merely a manifestation of the estrangement of mankind from nature, but a problem all of its own, arising from the spontaneity of capitalist reproduction.
Far from being unreal (see Ted's 3rd para, below), the different eras of human history are the only reality. The ideal of the species-being is a dream, at best an inverted projection of the actual movements of human history. Nothing is pre-ordained. The future is whatever we make of it.
Ted wrote:
The "internal relations" constitutive of each stage of development produce "essences" understood as particular forms of "self- estrangement," i.e. particular forms of divergence from the "species- being" - the "idea" of humanity in Hegel's sense - actualized by the ideal "internal relations" that constitute "communism."
These forms are "activities" in "internal relations" (all being is "activity" in "internal relations") - "processes" - as in the capitalist "labour process" constitutive of wage-labour. Marx, again sublating Hegel (as he himself points out in the passages I recently quoted), treats them as "educational," e.g. wage-labour is a "steeling school." They develop the "species-powers" constitutive of human "species-being."
The "essences" constitutive of "self-estrangement" are therefore only "real" as expressions of a "necessary" developmental stage; the "internal relations" constitutive of them are developmental relations that eventually lead to their "annihilation." Only human "species- being" is ultimately "real."