Evolution, Sex and Pain. Multiple Faces of the Dice

Suppose we are talking about pain. Humans feel pain, but what about a fly or an octopus? How similar are our nociceptive systems? And what about the reproductive system? Humans have two sex chromosomes, but what about other animals? How similar is the number of chromosomes throughout the entire animal kingdom? The two systems are very different in appearance but conserved, in part, throughout evolution. Although different, the essential mechanisms for life overlap and exhibit common patterns between species beyond chance. Adapt or die, in the purest Darwinian style.