So evolution is based on the premise that successive mutations lead to phenotypic changes ultimately resulting in varied species. This despite the fact that many mutations in nature are actually deleterious to that species. The question I have then, is that if mammalian evolution produced successive varied generations of species, starting from a common origin, why have bacteria not done the same.?Particularly with conjugate reproduction, E.coli for example, despite >10 to the 12th [Observed] generations have not essentially been transformed though there are species specific variations, particularly antibiotic resistance. (in other words, E,coli have not evolved into paramecia , for example) So then how can mammals, from their common point of therapsids, have evolved so many species with only about 6 million new generations from point of origin to current?