Unless we simply (?) mean biological processes: e.g. "Not breathing is against human nature" (i.e. the nature of a living human being). But Communism? Capitalism? (Any -ism?) And "human nature"?
Your mind consists of biological processes; indeed, all human behavior is a biological process.
It's important to understand human nature, so that we know what types of social and economic systems will work for us, but people cannot be described simply with either the amoral egoism of capitalism or the utopian generosity of capitalism.
But I just wanted to say that it's always seemed to me that the intention of communism was more in line with the way families work than capitalism. Because families do that "from each according to her/his ability, to each according to her/his need" thing. Well, most of them. The good ones, anyway. Then again, the fact that a lot of people can't even be good to their own kin sort of proves that a larger, national version of that doesn't stand a chance.
The vast majority of people have always been more generous to their own families than to strangers, which is only to be expected given the nature of evolution. However, we generally deal well with friends as well as family, but as you suggest, scaling our behavior from a small group of people we know to the anonymous millions of the nation state is the real issue.
The size of the neocortex in primates is closely associated with size of living group. Lemurs, with their small neocortex, typically live in groups of less than 5, while chimpanzees, with their four times higher ratio of neocortex to brain size, live in groups of around 55. Most other primates fall between the lemurs and chimps, but we're the exception, with the largest ratio. Following the pattern, the large human neocortex indicates that we should live in groups of about 148, and indeed anthropological censuses of hunter-gatherers and subsistence farmers lived in groups of about 153 and Neolithic Middle-Eastern villages housed between 120-150 people. Even today, business management studies show that companies function well on a person-to-person basis up to 150 people, and American Hutterites split and start a new colony when their community reaches the size of 150.
However, we're an adaptable species, so we've used another part of human nature--our innate understanding of language--and built bigger communities using the concept of hierarchy, dividing society into layers of authority, and we've learned to deal with people impersonally. Of course, both of those social adaptations have had costs, some of them deep such as the tremendous destruction we inflict when we scale up our tribal conflicts to modern wars. However, another one of those costs is attempting to develop an equitable and sustainable economic system, bringing us back to the original topic of the old systems capitalism and communism that we started with.
The way I'd like things to be is somewhat capitalist with much more broad and deep social services than we have these days in the States. I want universal healthcare. I want the minimum wage to be a livable wage. I want scholarships and/or job training programs for poor folks.
I tend to agree with maudmac, at least in general, that we need to balance the various facets of our economic human nature: reciprocity (returning favors and detecting and punishing cheaters, which is why people are so incensed at the fraction of percent of the budget that goes to welfare fraud), generosity, and greed. We can't base our economy simply on the honor system of communism, but we also can't ignore the poor in general as capitalism and our tribal instincts would suggest because we don't know each and every one of them.
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"Omnia mutantur, nihil interit." -- "Everything changes, but nothing is truly lost."