Survival of the Fittest
At the core of Social Darwinism and the theory of Natural Selection is the notion of the survival of the fittest. In research papers on the concept of the survival of the fittest in a thriving economy, two things are necessary: a competitive market and a division of labor. It is assumed that competition forces firms to make better products. But, this requires enhanced efficiency; thus, labor is specialized. Employees in a product assembly line all have their specialized trades: welders, operators, engineers, managers. Specializing enhances efficiency by doing what you are good at and doing it well on a consistent basis.
The theory is then extrapolated to entire markets and ultimately nations. That is why so many favor trade agreements like NAFTA and GATT. Each country specializes in what they are good at and trades for what they lack.
Charles Darwin uses his survival of the fittest concept in his book the Origin of Species. He argues that organisms with specialized traits are always more effective at surviving due to the specialized trait. For this reason, plants evolved such that pistils and stamens (that is, the male and female characteristics) appear on totally different plants of the same species. Darwin calls this the “physiological division of labor”.