Helix, you are mixing up the reality of species with the fantasy of a common ancestor for all life.
The definition of species usually takes the form of 'isolated interbreeding population' or something along those lines. It is a very argued-about definition.
But speciation is a funny thing. It depends upon breeding cues and not on DNA or morphology. For instance, because dogs and horses pick up their breeding cues via smell, they are willing to breed with any dog or horse type, respectively, which smells right. Thus, all domestic dogs, regardless of size, other appearance, or even DNA, are considered one species. However birds pick up their breeding cues -- in addition to the time of year -- from sight. Thus slight variations in coloring or size can determine an entirely different species, such as with hummingbirds. It takes an expert to tell one species from another, for many of the variations are so slight. But they are everything to the birds and the Anna will not breed with the Rufus. Now I can tell those two apart, but there are a number of them I can't. But it sure is easy to tell the different varieties of dogs or horses apart, isn't it?
So do what you want with species!
However the fact that there are variations within types or kinds of animals in no way supports the idea of a common ancestor for all. We have no evidence of that whatsoever in genetics, in history, -- no matter where.
The simians are distinctly different from us and we were never a part of a common ancestor in the past. Homo sapiens are homo sapiens and we were created that way, despite differences in appearance.