I am questioning the point of view that a zygote is a human. Most people who assert this claim to do it from a religious perspective but biblical stories indicate that babies weren't considered people until several years old... Probably due to the high mortality rate.

Other stories indicate that if a woman cheats on her husband she should be given a potion which was supposed to induce miscarriage.

If you are arguing from a purely agnostic point of view then it changes the debate into something else.