one common statement in popular science when speaking about evolution is that we all derive from a common ancestor, the "original eve". while a posteriori, it is true that mitochodrondrial DNA allows to trace back common ancestors in our heredity, it is certainly overstated. When thinking evolution, our focus is to look back from the present to our origins, but a the time of these "few" original eves, many different eves coexisted and acted -as parts of the whole population- in the evolution.
Evolution is more like a Banyan tree than a graph written on a board where species evolve from primitive forms into more and more complex forms, including an idealistic vision of our position on this tree.
even worse for the gap between reality and popular preconceptions about evolution: evolution is also lateral. More on this subject @ Horizontal and vertical: The evolution of evolution