Why does the arc of evolution bend towards complexity? Is there a logical explanation as to why this is beneficial or why it occurs? I know the question implies human motives to the evolutionary process, but it seems counterintuitive in a way.
Evolution tends towards more complex forms because usually what is being selected is greater functionality (i.e., eyes that can see better/clearer/in different environments, etc., or limbs that can help you run faster, etc.) depending on the organism and the selection pressures. Usually greater functionality requires greater complexity (i.e., more specialized cone and rod cells). However, as a paper this year demonstrated you can also get greater functionality from "subtraction" or less complexity. I wrote about it here.