Darwinism us usually thought of as "natural selection." If a species weren't suited for an environment, They would be overrun by nature and die. An example would like so: A group of wolves live in a mountain in the summer. One specie of wolves don't grow as much fur as other wolves. By natural selection, when it comes to winter, they will eventually die as they are not suited for the winter. Social Darwinism is when a group of species work together to survive. This applies to the more social world usually with humans. Humans build houses for other people to live in during the cold winters and people make air conditioners to survive the hot summers... But apparently, to afford all of that, you need money. So only the wealthy, or the "fit" can survive.
Darwin looked at slaves as different people because of their skin color and behaviors. In fact, Everyone was hypnotized to think of them as outsiders and inhuman because the way they act. So Darwin thought that black people were of different species and developed differently. Today, colored people are actually regular people. The reason why slaves back then were acting like they were back then was the way that they were treated as, property and not as humans. Slaves were angry and that behavior then made Darwin to look at them scientifically on their origins, where they came from.
The term Eugenics was actually invented and coined by Francis Galton, a cousin of Darwin. He himself was influenced by Darwin's theory of natural selection where nature decides which animals will be living. Basically eugenics itself is the study to select which people should breed in order to make a brighter future. Eugenics is an extension to Darwinism as it tries to improve it. So, Darwinism does contribute to Eugenics.
