During the late 1800s, the idea of social darwinism was used to explain the what?

A philosopher from England named Herbert Spencer took Darwin's original idea of evolution of plants and animals and applied it to the idea of economics, some people consider this application of the idea a little extreme, but was represented and associated with other common terminology in relation to capitalism like "laissez-faire" from the the French, meaning something along the lines of leaving it alone or letting it be, like the markets will take care of themselves and self-regulate accordingly.