was improbable, inexplicable, and altogether bewildering. He was an insoluble problem. It was inconceivable how he had existed, how he had succeeded in getting so far, how he had managed to remain—why he did not instantly disappear.

This illustrates the idea that Darwinism is a logical and scientific process that hinges on the pragmatic survival of organisms by adaptive means. In this passage, Marlow cannot fathom the generations of tenacity and adaptive solutions that have led to the emergence of the person before him.

There are numerous passages in Heart of Darkness that allude to the theories of Charles Darwin and their subsequent variations. One such modification is Social Darwinism. Not only scientists and social reformers but also many diverse agents of colonialism and European political and economic control used the concept of evolution to justify taking what they called the benefits of "civilization" to people they considered less evolved than themselves. These social evolutionists conceived a racial hierarchy that favored white Europeans.

On one of the occasions when Marlow observes a group of African men and, in his mind, compares them to the group of European men with whom he is traveling, he refers to the Africans as "prehistoric." This implicitly refers to Darwin's theories of evolution because it classifies the men at different developmental stages, in contrast to the Biblical view of creation.

The prehistoric man was cursing us, praying to us, welcoming us—who could tell?

Near the novella's end, Marlow reads the report that Kurtz wrote about supposed social reforms, which promotes genocide. It is intended for the "International Society for the Suppression of Savage Customs." This title is a thinly disguised version of the actual organization that was established under Belgium's King Leopold II, to support his country's domination of its Congo colony: the International Association for the Civilization of Central Africa.

This foray might be rather expansive because different people will see different aspects of Darwinian thought in Conrad's Heart of Darkness.  One particular quote that can be seen that might have applicability towards Darwinist ideas would be in the description of the enslavement of Africans: "Your strength is just an accident owed to the weakness of others.”   Darwin's theories were predicated upon how "species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce." The quote's discussion of Belgian superiority to Africans in the Congo as rooted in exploitation of weakness can connect to Darwinian ideas of competition and survival.  In this light, one sees how slavery and imperialism in the book can be connected to Darwinist ideas related to how organisms compete and, in the case of human beings, seek to dominate others through strength pitted against weakness.

Another aspect of Darwinist thought is rooted in how evolution takes place over a prolonged period of time.  Darwinian theory is based in a geological time frame, sometimes spanning billions of years.  The human predicament seems puny and insignificant when placed in such a context, and in the book's exposition, Marlow articulates such an idea:

No, it is impossible; it is impossible to convey the life-sensation of any given epoch of one’s existence--that which makes its truth, its meaning--its subtle and penetrating essence. It is impossible. We live, as we dream--alone.

Marlow's articulation regarding "the epoch of one's existence" helps to define how human experience must be placed in a larger context.  Darwin would concur with this because the scale of his evolutionary theory takes place over a prolonged and expanded period of time, a geological scale in which growth and development is nearly impossible to envision.  It certainly dwarfs "one's existence" because it helps to place biological change in a larger, more expansive, context.  While Darwin might not necessarily embrace the idea of being "alone," the reality is that when one sees time as Darwin would, bonds dissipate, connection is placed in a larger configuration, and time becomes the only constant.

The emphasis on time as a quantity that almost defies calculation and measurement is seen in another quote from Marlow.  The beginning of the work, where Marlow is almost a sage- like Buddha figure reveals another Darwinian construction:  "We live in the flicker -- may it last as long as the old earth keeps rolling! But darkness was here yesterday.”   The idea of seeing "the old earth keep rolling" speaks to Darwin's constant notion of change and evolution within the consciousness of organisms.  There will always be change.  Organisms live within this evolutionary reality.  While human beings might believe in their own sense of power and commanding of the moment, it is but a "flicker" when seen in the context of evolutionary time.  This time- based emphasis places human endeavor in its rightful spot, something that Darwin would embrace in his evolutionary theory.