Start of Human Life

When does human life begin?

I am interested in this because I am pro-life, but there is so much debate around when life starts in utero - when there is a heartbeat, when a certain number of weeks have been completed, when a baby is born, etc.

As a Christian, I believe that God creates life from conception. But this holds no weight in non-Christian circles. So I would like to hear from the scientific community if there is some point recognized by non-theists when an individual is separate & complete from his/her mother, even if not fully developed?


Hi Debra, nice question!
When you mention ‘life’ in the context of conception and birth, you are talking about life in a biological / physiological / medical context.

The problem with the question “When does life begin?” in this context is this: we do not have an acceptable medical definition for the more fundamental question, “What is life?” How then can we adequately answer when this thing called ‘life’ begins?

As a person who has dealt with numerous end-of-life issues and brain-death, the other question that I have struggled with medically is “When does life end?” We don’t have a satisfactory answer for when life begins or ends because we do not have a satisfactory answer for what life is in the first place.

Many attempts have been made to answer this fundamental question - ‘what is life’ in biological or medical terms. In modern science, when DNA was discovered and its mysteries unravelled, DNA was called the basis for life…until we discovered organisms without proper DNA. Earlier philosophers called ‘breath’ the evidence of life, or ‘humours’ or other ethereal imagined or real things. Today, in medical terms we say a person has life as long as there is electrical activity in the heart, or EEG waves in the brain or active oxygen exchange in the lungs etc. But all these attempts have proved inadequate in actually defining what life itself is. And that is because ‘life’ itself is something that is beyond the scope of material and biological investigation and we need to enter into the philosophical and metaphysical realm of discussion to answer this.

And that is where the problem lies. When we do not know what life is, it is anybody’s guess as to when it begins or when it ends, which is why we have such vociferous proponents in favour of and against contentious issues such as abortion, euthanasia, pro-life, pro-choice etc. Some say life begins at conception (when the zygote is formed), or when the embryo develops spontaneous heart beats and circulation, some say at separation from the mother at birth, and some modern naturalistic medical specialists go so far as to say only in late childhood when consciousness is supposedly formed (and we still don’t know for sure what consciousness is!!). There is no universally accepted consensus on this though many claim there is. It is still a matter of faith, educated guesses and derived conjecture even in medical circles! The accepted conventions for beginning and end of life are formulated only for the purpose of defining terms for medical procedures and decisions, not for arriving at a definitive answer.

The Biblical understanding of life is that it begins in the womb (perhaps at conception, or even before it), it proceeds from and is a gift of God. Even if we do not understand it fully and can still debate and quibble, two things are certain from a Christian viewpoint - 1. life is precious and 2. we do not have authority over it, either to give or take it. Christ said of himself, “I am the way, the truth and the life” (John 14:6). He alone has authority to give and take it. We are only caretakers of this wonderful and mysterious gift.

Psalm 139: 13-16
For you created my inmost being; you knit me together in my mother’s womb.
I praise you because I am fearfully and wonderfully made; your works are wonderful,
I know that full well.
My frame was not hidden from you when I was made in the secret place,
when I was woven together in the depths of the earth.
Your eyes saw my unformed body; all the days ordained for me were written in your book before one of them came to be.



Thank you for your wonderfully informed response! I did not realize how complex the answer was - even from a scientific viewpoint. Someone who was training to become a doctor once told me that the beginning of life according to his biology textbook had something to do with when the DNA of the baby in utero formed (separate from the mother). I am NOT a science-oriented person, so I am probably not remembering correctly. But I was hopeful that scientists could agree on a moment in time when the baby had its own “identity.” Is that the same point in time when the zygote is formed?

I can see that for me to discuss this with anyone is out of my league, but your reply has helped me to understand the various issues around the question of “life.” You have also helped me to see the connection to the question of when life ends…I will remember your statement regarding both, "we do not have authority over it, either to give or take it."

Thank you,



Hello Debbie,
In answer to your question, yes, the zygote is formed at the time of conception and has it’s own DNA package (half from mother and half from father). That much we know (by the way, I am not an expert in genetics). Now, does that translate into a separate ‘identity’ - that is a matter of conjecture. The question now arises - what is identity? These are the kind of questions that lead to more questions as we try to answer them. The issues of consciousness, conscience, guilt, sense of self, life, death etc.- we talk about these all the time but defining them in terms of naturalistic material science is very difficult.

In fact, some of the most important things in life are also the most difficult to define or answer satisfactorily using the methods of scientific enquiry - beauty, truth, justice, righteousness, love, humility etc. Yes, the scientific method has given us several great benefits (and also great harm) but it falls woefully short of answering the most important questions of life.


Thank you, Tony, for your timely, informative, & very helpful answer. It’s wonderful to have some place to go with questions & feel that I can trust the answer.

With appreciation,



Thanks for your question Debra.

What I’ve found really interesting about this debate is that there’s only really significant debate about this question when abortion is mentioned; in general medical science, there is not really any debate about this at all. What I think this shows is that the science is clear: life begins at fertilisation/conception - but that, realising the political/ethical implications this has, people have tried to claim that we don’t really know.

As evidence of this, consider the very long lists of textbooks and journal articles stating that a new human being is formed at fertilisation in these three links:

And finally (and perhaps most persuasively), there is a recent survey from 2018, where a University of Chicago PhD researcher surveyed thousands of biologists across the world (
95% of these biologists affirmed the position that life begins at fertilisation. Even the overwhelming majority of pro-choice biologists agreed with this position. I think this clearly shows that the scientific view is that life begins at fertilisation, but that people have tried to make this seem unclear for largely political reasons.

I hope this helps!

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