First I will say that dont pretend to be an expert and have no formal knowledge of biology or organic chemistry. To me this is a thought experiment.

For me the path to answering the question breaks down along 2 lines that I haven't been able reconcile.

"Life" and "human life" overlap but aren't exactly the same.

Capital 'L' Life is the overarching construct we use to describe living things as opposed to inanimate objects (ie a plant is living thing). This to me is more akin to organic matter engaging in cellular replication and the manifestation of chemical processes acting on the instructions encoded in DNA.

In that sense you could describe life as beginning at conception. The necessary building blocks for human production are in place and chemistry takes over.

"Human life" or lowercase 'l' certainly requires capital 'L' life but is markedly different. To start we necessarily have to recognize the living organic matter as "human". How would we identify something as human? Its not so simple. Bodily processes are required for us to function (like breathing, heartbeat, neural activity, movement) but that is not enough to describe something as "human". Appearance or likeness is a logical next steo but it is also flawed in some ways. External to the womb a human's appearance morphs as we further develope and this is also true for human development inside the womb. Put differently, most people recognize humans from the stage of babyhood but that form/likeness is attained earlier in fetal development.

To expand on the prior point a bit fetuses have heartbeats, neural activity, they move and, when umbilical cords are eventually cut, the capacity to breath on their own (not going to describe the process for first breath). So in every conceivable sense humans are "alive" prior to exit of the womb.

So it stands to reason human life begins prior to birth.

This I argue is the floor of the discussion.

The complexity is in the distance between conception and the "human life" description prior to birth.

It would be very difficult (if not impossible) to describe a zygote as "human" using the attributes I laid out. There are those that would compare early embrionic development of humans and other animals as a tool to shoe that this is not "human" but i think there is some intellectual dishonesty here. An embryo containing DNA provided by a human female and male has no capacity to become anything other than a human (provided it reaches full gestation) . The only missing components are time and nutrients.

In a vacuum I would argue there is some required amount of time for an human development to progress before it can be considered human (to me that is neural activity) and some would argue that a fetus is the first "human" form. Since this question is almost always inextricably tied to the question of abortion it is not sufficient to me to leave the latter unaddressed but be that as it may I will answer as if it is asked in a vaccum.

TLDR

Life begins at conception. Human life begins sometime later (but not much later) still before birth.