"Surely the "scientific" answer as to when life begins, is the moment the sperm penetrates the egg?"

Perhaps...but that is not really the issue that most who oppose abortion are concerned with. There is the usually unspoken assumption that some sort of 'soul' enters that Morula. This is a religious assumption which not everyone agrees with. There is a secondary issue about when that collection of cells becomes a 'human' and can survive outside the womb. Even then, there are VERY complex issues which depend on medical facts and culture.

You want one? Read about triploid. I have firsthand experience with that one.

You cannot reduce the answer to the 'morality' of these things in any simple way!