A Believer becomes new creation at the point of salvation, but that new man does not automatically have control over the old, but still present, sin-nature. Sanctification is the process of putting to death that old sin nature so that Christ can reign in us… a Believer with God's Word incorporated his/her heart is Word-driven and Spiritually centered, free from the power of sin.
It is here, I think, that Biblical theology comes most in conflict with macro-evolutionary ideas. There is such a concept as "Theistic Evolution" which essentially claims that there is no necessary contradiction between Biblical theology and Darwinian-type evolution.