Charles Darwin's *On the Origin of Species* didn't "justify" anything in the sense of providing moral or ethical justification. It was a scientific work that presented a theory about the natural world, specifically how species change over time.

Here's how it can be interpreted:

* It justified the theory of evolution by natural selection. Darwin's book provided extensive evidence and a logical framework to explain how species evolve through the process of natural selection. This was a revolutionary concept at the time, challenging the prevailing view of creationism.

* It provided a scientific explanation for the diversity of life on Earth. Darwin showed how variations within species, combined with environmental pressures, could lead to the development of new species over generations.

* It challenged the traditional view of human exceptionalism. Darwin's theory implied that humans were not separate from or above other life forms, but rather part of the same interconnected web of life.

However, it's important to note that Darwin's work was often used to justify certain social and political views. For example:

* Social Darwinism: This philosophy used Darwin's ideas to justify inequality, racism, and imperialism, arguing that "survival of the fittest" applied to human societies. This interpretation of Darwin's work is now widely considered to be misrepresented and harmful.

Ultimately, Darwin's *On the Origin of Species* was a scientific work that fundamentally changed our understanding of life on Earth. It provided a powerful explanation for biological diversity and evolution, but its impact extended beyond science and contributed to complex social and political debates.