Classes developed within classless populations of hunter/gatherers as agriculture and animal husbandry were brought into being--products of human labour and innovation. This occurred first around 10,000 years ago when humans began their march out of a total dependence on hunting, fishing and gathering within Nature alone, towards class dominated civilisation in which human beings had some certainty and control over the security of their food supplies, which had previously been left to the dependency structures demanded of humans adapting to their immediate, multiple Earth-wide environments; the exodus out of Africa put humans everywhere by 8,000 BCE. This was the moment when humans first discovered that certain plant foods could be domesticated, along with the possibility of domestication of certain animals. Breeding domestic animals was, I think, the beginning of a 'scientific' understanding of reproduction amongst humans i.e. the parts which males and females played in the process, which beforehand had remained ensconced, within the sphere of human reason, in mystified religious explanation.
Within pre-agricultural society, political power remained at an egalitarian level. Along with the politics of dominance and submission, based on private ownership of wealth which mark the generation of class society, came other dynamics of unequal political power, most especially that between men and women. Patriarchal systems of dominance and submission sprang from necessities born of maintaining the dominance of the class of appropriators of wealth over the producers of wealth. During the earliest ages of planned production, the political dominance of owners of food surpluses of domesticated plants and animals grown and raised on their private land over and above that of the immediate needs for sustenance of producers themselves became the accepted norm. These owners of food surplus became the first ruling class. The mutual recognition amongst humans within their communities that private ownership of surplus was just, led to rules/laws for maintaining and protecting the priority of private ownership of property/wealth over possible communal need, an aspect of human social relations absent in the classless hunter/gatherer societies. This dominance (inherently an aspect of political power) was and continues to be maintained through force and violence or the implied threat of same within the social relations between human beings organised in political States. This phenomenon also occurs, most often murderously, within the political boundaries of so-called, 'failed States', e.g. 2012 Somalia. The violence inherent in the political relationship between men and women flows out of the ownership of surplus wealth and the mutual recognition inherent in sustaining private ownership of same. Within this mutual recognition, lie the seeds of the modern political State, the form of government within civilisations based on class rule and the maintenance of patriarchal forms of marriage.
Class rule is perpetuated in the patriarchal organisation of class society and justified to its members on the basis of the need to identify offspring in the male line in order to pass on accumulated wealth. Monogamy and polygamy become the only legitimate forms of marriage recognised within class society's political State. These marriage forms are a direct result of the dynamics of unequal political power fundamental to the establishment of class divided society. They reflect a legitmation of male control over the female and a generalised preference for maintaining male ownership of lion's share of the class society's collectively produced wealth. And with wealth comes dialectical opposite, political power. (I realise that there have been exceptions to this rule in history e.g. Queen Elisabeth I, Gina Rinehart, Cleopatra and so on.)
Applying a dialectical analysis to what is known today as 'identity politics', one can logically discern the interconnection or unity of opposites within the various levels of the universal, particular and individual. On the universal level, we can start with living beings. Amongst the living beings, we can logically separate life into plants and animals--flora and fauna. The totality of life, of course, continues to exist, independent of our efforts to logically grasp particulars and individuals within it. Amongst the animals, we can logically separate forms of life into various species, including, human beings. Most animal types are divided sexually between male and female. Exceptions, of course are those animals such as amoeba which replicate through self division. Amongst humans we can further logically divide, in our minds, necessarily connected opposites or unities into classes, based on the producers of wealth and the appropriators of same.
The differences between identity politics and class politics start with differing philosophical dynamics. Identity politicos are committed to positively maintaining themselves as a particular ideological subset within the totality of humanity. Class conscious workers are committed to negating themselves as a class and with that material feat, the elimination of the ideological subset of class. Whereas the practitioners of identity politics emphasise the positive differences between their particular identity and those who are not of their identity, maintaining and recognising their identities of ideological subsets in the present and into the future; class conscious workers see the need to differentiate between the class interests of those who produce wealth from those who appropriate the lion's share in order to end this macro-dynamic of political power. Ending the political domination of one human being over another is the end result of negating the class dominated civilisation. Equal political power between all human individuals is communist praxis.
To be sure, a worker can be for negating the negation of class rule while embracing some particular ideological subset of humanity. Most individuals in this day and age identify themselves with one or more of these ideological subsets e.g.: the national, the religious, the political, the philosophical, the professional and so on. Most individuals mentally place their various ideological identities into some hierarchical priority. Most individuals who engage in identity politics, not only self-identify as this or that part of the myriad ideological subsets of humanity, they also identify other human beings as belonging some ideological subset of humanity, whether they, the others, want to be so identified or not. A prominent example is race. Although, most anthropologists and biologists would agree that there is only one race amongst human beings, the great mass of people have been socially schooled to identify two, three or more races amongst humans. On the positive side, one human will identify him or herself as being 'white' or 'black' or 'red' etc. By positive, I don't mean 'good', I mean more or less the affirmative, a 'yes' to the question, 'which race are you?' followed by the answer, 'I am this or that separate race.'
Identity politics have everything to do with saying, "I am". Identity politics become for many individuals, a preferred escape route from the social alienation and oppression which are generated within the power dynamics of class dominated civilisation and its governmental expression, the political State. The longed for community (Gemeinschaft), which humans lost when they developed class dominated civilisation, expresses itself in stunted form with identity politics. Identity politics can lead in all kinds of political directions, from a conservative's embrace of a particular nation State or race, to a liberal's love affair with celebrating the diversity of 'races' (which don't exist on a biological level) and nation States, which after all, are the governing structures of class rule.
Identity politics are about preserving an ideological subset of humanity, of positively identifying one's self or one's perceptions of others as being something other, more than 'just' another alienated individual human being in class society. Within the scope of identity politics comes the struggle to place one identity's priority over another identified subset. Thus, in racist politics, one race is given priority over another. In sexist politics, one sex is given priority over another. Where physical power to coerce is non-existent, moral suasion is used to promote political hierarchies of identity. In the dynamics of political power, dominance and submission always come into play. With moral suasion comes brow beating guilt into those who will not submit sufficiently to the other identity's perceived priority. Thus, the inherent tie to class dominated civilisation's social psychology of sado-masochism continues to be generated through identity politics. As a result, the possibility for members of the working class to see themselves as the producers of all wealth not found in Nature and emancipating themselves from the exploitation inherent in the wage system i.e. making a social revolution for themselves, is retarded at best and at worst is squelched from yet another direction.
About 10% of the population, the ones who scarf up over 70% of the world's wealth--the ruling classes on our planet, who, along with their flunkies, are the ones who benefit from maintaining the rule of the social relation Marx called Capital.