Strange conversation

I'm in the midst of a protracted argument about the moral status of the human embryo with someone who supports abortion rights (in the comments of this post). The discussion has been all across the board, but of late I'm trying to get him to acknowledge that human beings begin to exist at conception. He has advanced the most curious argument that this is not the case, because the matter that I consist(ed) of existed prior to conception, in the sperm and ovum that united. The logical conclusion of such an argument is that every individual entity (including all human beings) are of the same age, and that age is the age of the universe. Here's what he said:

Life is a cycle. It doesn't have a tidy "beginning" the way you want it to have.

And then:

You didn't "start to exist" materially. You didn't "start to exist" intellectually. You didn't "start to exist" biologically (you didn't spring from non-living material).

This is probably the strangest argument I've ever seen advanced in the course of trying to deny that human beings have value from the moment of conception. I've heard the argument that "life is a cycle," but I've never seen someone actually continue to defend it in the face of a pretty straight-forward and effective rebuttal (i.e. that the issue is not about life as such, but about the life of an individual human being). Nor have I seen someone maintain that human beings don't begin to exist because the material that formed them was previously present.

At this point in the conversation, I'm just hoping he'll answer the question, "when did you come to exist?" I have some doubts that he'll do so.

Nonetheless, an extended argument with someone like this is useful for making sure I'm able to articulate my position. The question "when did you come to exist?" will prove useful in the future.