"At the funeral of Marx, Engels made much of the connection between Darwinism and Marxism, stating that just as Darwin had discovered the law of development of organic nature, so Marx developed the la of development of human history." -From Helena Sheehan's "Marxism and the Philosophy of Science."
With this in mind, and with Pannekoek's citations throughout the work-which include Kropotkin-it is difficult not to see an early attempt at synthesizing Marxism and Anarchism, here. This pamphlet takes both Marx's theory of development in history and combines it with that of Darwin's theory of organic development; Pannekoek does this by including Kropotkin's theory of mutual aid inbetween the two. Why is this interesting? It is fascinating because he is attempting to combine two of the fundamental theories of scientific socialism from the 19th century, one from political economy, the other from biology, and one associated primarily with Marxism, and the other with Anarchism (though of course there was and is overlap).
The first half of the pamphlet is an argument against social darwinism, pointing out, in conclusion, that it is the free market which produces conditions similar to that of "nature," in that it creates a desperate struggle for existence in society, allowing to the bourgeoisie to speak of higher and lower races by pointing out to the conditions they themselves (unknowingly) create. I do not find this dated, as the new wave of far right movements are returning to biological explanations to justify their racism. Capitalists also still appeal to "human nature" in their discourses, so in this regard, too, it is relevant. In the latter half, Pannekoek outlines the biological theories that point to the opposite tendency, namely, mutual aid and social feeling.
Etymologically, Pannekoek develops the similar origins of the word "tool" and "organ" to speak about the parallels between the development of organs in nature and the development of tools (machines, means of production, etc.) as a means of competition within capitalism. This, in itself, is a very interesting point and could be further developed. This is not a long work, and while simple, it is definitely an interesting starting point for further thought.