Evolution does not make a species ‘better’, but natural selection – the mechanism that drives evolution – selects for traits that improve an organism’s chance of survival and reproduction. The trouble is that ‘better’ and ‘worse’ are subjective judgements that don’t really apply to the blind process of evolution. During reproduction, every organism is subject to an infinite number of random genetic mutations, not all of which are positive. One mutation might kill an organism in its infancy, while another will help the creature become a more successful hunter. It makes sense that the successful hunter has a greater chance of mating and passing on its DNA than the animal that dies young. Over thousands and thousands of years, as more and more organisms with the successful hunter mutation survive and reproduce, that trait becomes embedded in the collective DNA of the species. The result is a species that is not necessarily better than its ancestors, but better suited for reproductive success.
Answered by Dave Roos