Absolutely true. Was responding to the last bit of your comment and ended up completely disregarding your greater context... sorry.
This is a bit of a hobbyhorse of mine at the moment, especially since so much of the discussion about ethics here seems predicated on the existence of terminal values that can't be interpreted in terms of anything else.
A few years ago, I wrote a little dialogue I imagined between 2 materialists, one of whom was for and one against abortion, centering on the personal identity question. I recently cleaned it up and added a number of references for the biological claims.
You can read it at An Abortion Dialogue.
Early feedback from #lesswrong is that it's a 'nicely enjoyable read' and 'quite good'. I hope everyone likes it, even if it doesn't exactly break new philosophical ground.