Evolution is the process by which animals, plants, and other living organisms are transformed into different forms by the accumulation of changes over successive generations. But despite centuries of research, scientists are still unable to fully explain in a single, definitive formula the exact mechanisms that govern the process. Indeed, evolution leaves scientists with more questions than answers.
The theory of evolution cannot be fully explained for a number of core reasons, not least because of the vast time scales involved and an incomplete fossil record. But there are other factors at play that make aspects of life's development truly puzzling. In short, there are several evolutionary mysteries that still baffle scientists.
In this gallery, we highlight 15 evolutionary phenomena that leave researchers and academics scratching their heads. Click on and see if you can figure it out!