At what point did sin enter? How did sin enter? What was the result of sin? Do we need a Saviour?
Yes, we need a savior. There was indeed a first man into whom God breathed a soul, but that first man had parents who didn't themselves have souls, i.e., his parents were anatomically human (same species) but were otherwise hardly distinguishable in their conduct from smart apes. Adam's wife, however, apparently didn't have parents (at least not as contributors to her genetic make up), since she was brought into existence via cells taken from one of Adam's ribs, although I suppose it's possible the fertilized egg from which she sprang was then implanted into the uterus of a soulless human female for gestation.
Adam's sin was significant because he was the father of all ensouled humanity, as the soulless humans were out-competed in the same niches by those with souls and have thus disappeared from the earth. It is the soul which makes us Adam's offspring. We inherited our souls from him. Our genes go back much further than Adam, however. Genetically, we and Adam both descended from the first life that spawned from the dust of the earth.
