Per Marx and Engels, every closed social order is doomed to one of two fates:

1. Self-annihilation due to its own internal contradictions.
2. A change from within which changes the mode of production and thus the class structure.

Change in mode of production is not just something we can decide to do arbitrarily. It is a response of the human organism to changing “enviromental” conditions¹, similar to what occurs in the biological evolution of species.

Change in the human social organism differs from that of biological organisms in the ways in which change can occur.

In biological evolution, change only occurs through death of maladapted organisms and the natural selection of the surviving organisms. Change then moves in the direction of the surviving organisms.

This happens in human society too, where maladapted social orders are extinguished over time through death of those social orders.

But this is only the slowest mechanism the universe has for changing to adapt to conditions. Intelligence in organisms such as ourselves is the basis of speedier mechanisms for changing without the death required by natural selection.

If natural selection was the only way change happened in humanity, political action would be meaningless and actually we should all become death-worshipping fascists, which is a logical endpoint of that belief.

Because of humanity’s ability to process information, deliberate, and crucially to project the likely outcomes of actions into the future without actually taking those actions, we can perform the “selection process” (and incorporate new information into the social order) without needing to accomplish that through the death/destruction of the social order.

For example, we can see through the Marxist analysis that the capitalist social order, if left unchanged, will lead to its own extinction through either despoliation of the environment or apocalyptic international conflict (like nuclear war). Unlike with natural selection, we do not need to actually experience these “deaths of the organism” to be able to incorporate the information of them into the functioning of the social organism. It is as if we “simulate” the natural selection process.

Based on the information that the capitalist order is doomed to extinction one way or another, we can then potentially act within the social organism to “euthanize” the capitalist social order without any actual harm coming to actual human beings.

At the level of the social organism, class struggle is the short circuiting mechanism which allows us to evolve without the pain and death of natural selection.

Why class struggle specifically? Changing a social order implies class struggle. This is simply because ruling classes have a tendency to resist changes to the social order that would undermine their rule, even if there is reason to believe the order itself is driving off a cliff. This is the case right now in capitalism where our ruling class is committed to the continued use of fossil fuels even as they continually destabilize life on Earth.

Therefore, sufficiently far-reaching attempts to “evolve” the social organism from within, via politics, tends to manifest as a class struggle, because it would involve the destruction of a class. Not the physical destruction of the people who make up that class, but the destruction of the social role corresponding to that class, which members of that class often identify with their own literal death, and resist accordingly.