From my understanding of evolution, there are several types of “selection pressures” that drive the gene pool in certain directions. For example, a peacock’s tail is the result of sexual selection from a peahen. A peacock’s tail is actually a huge disadvantage because it takes a lot of resources to grow and maintain as well as attracting predators. But it does one thing really well, it gets him laid, and that’s all that matters from the perspective of the gene.
Evolution isn’t just a “weeding out” process. Genes tend to be “pushed” by the environment in a direction that produces the best fecundity of the species. It may seem like just a process of elimination but there is quite a lot more going on under the hood. Sexual selection: Darwin & Fisher. Punctuated equilibrium: Stephen Jay Gould. Genetic drift: Sewall Wright etc.
Read “The Selfish Gene” and “The Blind Watchmaker” by Richard Dawkins to get you started.
Thanks for the comment.