Hmmm....
if I am understanding correctly...
DNA analysis can confirm whether one is part of Homo sapiens, like Jny stated...
yet
if you are asking whether science alone can in a foolproof way define "life" or what it means to be alive for any organism, there is a bit of an iffy area.
Biology theory teaches that living things must possess
certain characteristics to be considered alive.
This is sort of iffy too though.. Ive seen the list vary a little form book to book...also, researchers agree that strange pathogenic "organisms" like prions or even viruses (virtually genetic material packed in a protein capsule with an injectable needle...and nothing but) do not seem to fully jibe with these "characteristics of life".
Works for most organisms though.
The only area that you are implying that seems to me to exemplify the inability of science alone to decide whether something is or is not human life, is the question of the developing zygote/embryo/fetus.
Since this appears to be a spiritual judgement...at least from those who take a moralist Christian perspective, it is something that cannot be logically argued. Belief that a conglomerate of cells from conception constitutes a human being by God's right is a belief based on "truths" that cannot be proven. So in this one case, I suppose science alone cannot determine this... its a value judgment... at least most of those whom Ive debated with on this have argued that it simply IS a human being because God says so...
I have replied with what I thought were science-based counter-arguments... but mine probably have some humanistic thinking and a particular understanding of things in them too... so yes... whenever I have these debates, they do not seem to hold to a solely scientific ground... if any scientific principles at all...