> It is like asking: what is the evolutionary advantage of a broken leg? Sometimes things go wrong and the result is pain. Pain and femurs are the result of ov

> It is like asking: what is the evolutionary advantage of a broken leg? Sometimes things go wrong and the result is pain. Pain and femurs are the result of over 3 billion years of evolution from prokaryotes (the simplest of single-celled organisms) to modern humans. It's a good question: What was the advantage that led to leg bones, and in particular to leg bones that break under that kind and direction of stress? Why not stronger or weaker? Why not more shear and less compression strength? What was the advantage of a nervous system, including one that produces pain, and one that produces that amount of pain or continuous pain? > many kinds of failures show up after the typical reproductive window. There is little evolutionary pressure to prevent such failure mechanisms. Pain occurs throughout life. Also, after reproduction successful organisms, at least of the human variety, raise and prepare their offspring for life, and even the offspring of their offspring.