This argument demonstrates a misunderstanding of Darwinian evolution. The theory is that things evolve due to "natural selection," a process whereby survival of the fittest weeds out unfit specimen and selects for specimen that are most fit to survive long enough to reproduce. There is no purpose behind this. The moment that you suggest that there is purpose or design to evolution, you're no longer talking about evolution via natural selection and also no longer talking about the type of evolution that the scientific evidence supports.