Mitochondrial Eve and Y-Chromosome Adam lived thousands of years apart, they were not a couple.
The concept of Natural Selection, sometimes used synonymous with
"Survival of the Fittest, is often touted as the magic process that when added to mutation will result in advancing steps of higher and higher species and the success of evolution.
This is completely wrong, there are several "forces" operating as natural selectors, not only "survival of the fittest", in many species sexual selection by the females dictates the future of the specie.
In Evolution there's no "higher and higher species."
But it is never a process that will give you a new species.
This is pretty big claim and proof of this will give Nobel prizes, a place in History and a ton of money.
A clear modern example - Wolves on Isle Royale in Lake Superior.
This Island use to lack wolves but in 1949 a pair of wolves made it to the island crossing an ice bridge. The Island then had a wolf population starting from a single pair.
Then in 1997 another wolf, a male, crossed an ice bridge - and because he was fresh genetic material and not inbred, he and his offspring quickly dominated and now every wolf on the island is his decendant.
For the island, he currently is the source of mitochondrial Y - yet genes from the first male wolf are still present.
On a much larger scale the same is true for our species, we have numerous genes that do not come from our Mitochondrial X and Mitochondrial Y ancestors.