Human evolution is a lot messier than we thought

Evolution is the theory that a species changes over generations, driven by a process of natural selection. While the existence of evolution is not in doubt, its mechanisms and the forces that drive its mechanisms are still hotly argued. At the simplest level, a mutation can be fatal, benign, or confer an advantage. Say the genetic change enables a creature to thrive in a wider temperature range.

Theoretically, the advantaged creature will procreate more than its regular brethren and the mutated gene will spread in the population over time. But even the consequences of evolution are debatable. Humans like to think that evolution made us the smartest animals, but first if all we can't actually know we're the smartest. We haven't learned to communicate with other candidates. Secondly, some posit that our smarts will kill us all.Then there's the microscopic parasitic jellyfish that evolved backwards, from complex to simple, losing even its genes to breathe, and it is magnificently successful.