The instinctual roots of "Leftism" are more like resentment of anyone-else having more than me, than any positive desire for equality

Since Leftism is the dominant ideology in the world today, and Leftism often appeals to some principle of "equality" (however vague or incoherent) as the rationale for its actions; the instinctual basis for "equality" is a subject that warrants closer examination. 

This examination is something I attempted, from the perspective of evolution by natural selection, in an oft-cited theoretical paper I wrote many years ago.

[The inequity of inequality: egalitarian instincts and evolutionary psychology. BG Charlton Journal of Health Psychology. 1997; 2: 413-425.] 

My conclusion was that evidence from anthropological studies of "simple", nomadic hunter-gatherer societies - i.e. the most economically-equal societies ever known - was that their culture of equal-sharing (among those of equivalent sex and age) is not due to a positive valuation of "equality". 

Instead, the sharing was a consequence of what I would now term a double-negative ethical reasoning - for which I used the term "counter-dominance":  

...Equal sharing is enforced upon high status individuals by spontaneously-arising counter-dominant coalitions of lower status individuals (Boehm, 1991; Erdal & Whiten, 1994). Sharing may be a way of encouraging co-operation and preventing conflict (Franks, 1988); it would compensate low status males for their reduced access to females of high reproductive potential and can be seen as a way of "buying off" potentially hostile rivals who might otherwise refuse to cooperate or take hostile action...

"Counter-dominant" instincts (Erdal and Whiten, 1994 and in the press) operate in two ways: firstly to enforce equal sharing of resources, and secondly to be satisfied with an equal distribution of resources. 

In support of this idea, primatologists such as Byrne (1995), Kummer (1995) and De Waal (1996) have traced the evolutionary history of food sharing (and of other counter-dominant - and proto-moral - behaviours) through monkeys and apes to reach the highest (non-human) intensity and sophistication among the chimpanzees. 

Egalitarian human societies are therefore not without their social conflicts: their harmony is of the nature of a dynamic equilibrium between dominance and counter-dominance, both of which sets of instincts continue to operate, the equilibrium between which can be altered by a change of circumstance. 

In all human societies, even in egalitarian hunter-gatherer societies, the persistence of dominance instincts leads to recurrent attempts by high status individuals to dominate, take more than an equal share of resources, or hoard (Knauft, 1991; Erdal & Whiten, in the press). 

However, in immediate-return economies attempts by high status individuals to breach the egalitarian distribution and attain coercive power will readily be detected, and can be met by counter-dominant community alliances of lower status individuals (Woodburn, 1982; Boehm, 1993). 

Counter-dominant alliances may employ a wide range of tactics for mobilizing concerted opposition from the rest of the community in such forms as public complaint, ridicule, threat, ignoring the would-be dominant individual"s orders, or actual group violence against dominant individuals. 

Homicide is not uncommon (and difficult to prevent) in hunter-gatherer societies. Other alternatives include expulsion of recalcitrant individuals, or mass emigration to another band to escape domination. 

Such strategies are possible due to the lack of sustained power differentials underwritten by resource differentials - in immediate-return economies no one person can become so powerful as to be immune to counter-dominant strategies. 

But when - as in delayed-return economies - high status individuals can appropriate a greater than equal share of resources, they are able to sustain this inequality by building alliances among high status individuals; and by enlisting supporters (eg. a "gang" or "bodyguard") to create larger and more powerful alliances, trading the stored resources as payment for cooperation (Barkow, 1992; Gellner, 1988).

In sum - the distribution of valued resources, such as food, tends to be equal, not because equality-of-everybody is positively valued; but instead because me-having-less than anyone-else is negatively valued. And those who have less, immediately gang-up on anyone who has more then them; and compel him to share it out.  

If counter-dominance is an approximately-correct explanation of the instinctual basis for "equality"; then it readily explains the observed structure and behaviour of modern Leftist ideology.

A close synonym for counter-dominance could be a spontaneous resentment at others having more than oneself; coupled with a tendency to form alliances with others having similar grievances against those who have more. 

Insofar as this is instinctual, it operates on people and situations in a person's perceived environment - which nowadays includes (and is perhaps dominated by) the "virtual" environment of mass and social media - reinforced by the "real life" social world of gossip and interaction, that so often takes up and amplifies themes from mass/ social media. 

For me, this idea of a double-negative, and resentment-based instinct helps explain the incoherence of Leftism - in that "The Left" is a collection of people with a collection of grievances, each rooted in the belief that anyone else having anything more of what I want is an "unjust" state of affairs. 

It is this instinct which leads to the supposed ethical principle of "egalitarianism" - that is manipulated by political leaders, in order to control (and weaken) the masses. 

Because, in a mass modern society, with multiple valued resources, there are many overlapping (hence incompatible) demands for equal sharing among many overlapping groups. There is never any greater equality in modern societies, and indeed this state is logically impossible because incoherent; but a there is instead a continual state of resentful complaint about inequality - as predicted by counter-dominance being at the root of it. 

And this continual state of resentful complaint is positively encouraged and reinforced by (and as) the value-system of Leftism.  

From a Christian perspective, we can see that resentment is a sin, indeed the master sin of modernity; and therefore that (insofar as the basis of equality really is counter-dominance) Leftism is rooted in evil motivation.

An evil motivation that is spontaneous and instinctive, hence powerful... 

Nonetheless, no matter how natural it may be (all sins are "natural", after all!); resentment is an evil that ought to be repented and minimized - not celebrated and encouraged.