Evolution explanations fail to satisfy me. I have a different perspective. Rob is old and has a child that has a child. Rob is of the old human species and Rob is about to become extinct. The old variety of humans is now extinct. It began long ago. The current model of humans will be extinct and will be replaced by the future model unless there are no future humans. Humans are quite different from the first human group that appeared. I think it is a group of humans that were the first humans. It did not start with a single individual or with 2 individuals that mated. It is a group of perhaps several hundred that continue to have offspring and each generation that becomes extinct is replaced by the offspring generation. Later we were separated by geographic division and the traits of modern humans varied with each separated tribe over long periods of time. We are still all humans however. Dogs have even more variation in the separate breeds. They are however still dogs. Dogs can be bred with wolves that they deliverged from. This means they are still very similar to wolves.
Humans could separate into subspecies like what happened with Chimps. There are Bonobo chimps and common chimps. We classify these as separate species.