From the Christian perspective, "human life" = "immortal life;" and to use traditional theological language, understood as immortal, human vs animal life comes into existence with ensoulment. The immortality of human life does not come into existence as the result of the evolution of homo sapiens, but is a unique creative act of God in each and every instance of each and every human person. 

We have no revelation as to when ensoulment occurs, so over 2000 years, theologians and philosophers have attempted to infer when ensoulment occurs on the basis of whatever biology was available to them in any given century. With the modern discovery of DNA and the fertilization process, in our time the Church faceted on conception as the biological moment when ensoulment seems likely.

Relatively recent information to the effect that as many a 75% of fertilized eggs are unable to implant and are thus thus naturally aborted is beginning to raise doubts about this assumption.