According to Wikipedia, "evolution by means of natural selection is the process by which traits that enhance survival and reproduction become more common in successive generations of a population." Tardigrades have been around for 530 million years. Their survival skills are obviously impressive. But it seems that as species become more complex, their survival capacity declines. Now, I think it pretty obvious that species have evolved over time. But I wonder if the survival of the fittest dimension of Darwin's theory perhaps needs some refinement. I suspect that Teilhard de Chardin's notion of complexification may be nearer the truth.