Humans are placental mammals, and we debate whether life begins at conception or birth.
But what if humans were marsupials? A Kangaroo is a marsupial. It gives birth after 5 weeks. The fetus actually has to crawl from the vagina, thru the mother's fur, and make its way into the pouch and begin feeding off a nipple. At 5 weeks, a marsupial fetus is capable of doing that. Would that constitute life? Would it be murder to kill a marsupial fetus as it crawls across its mothers body to feed? Or is it only murder once it is strong enough to forage for itself outside its mother's pouch?