Does life begin at conception?

Okay, let's break this down. The most common thing I hear about a fertilized egg being a "person" and how life "begins at conception" is this argument that "it's a living thing in a woman's body that has different DNA". There's a big problem with this.

That's also an apt description of a cancerous tumor, or a parasite. If this is really what you have as your argument, then you are effectively arguing that we shouldn't treat cancer and we shouldn't try to remove a parasite. Is that what you want?

"But the 'unborn baby' has human DNA!" you respond. Yes, this fertilized egg has human DNA, but do you really want to call anything with human DNA a "person" and claim that killing it is "murder"? Biologists and doctors estimate that fully half of all fertilized eggs fail to survive nine months for purely natural reasons, most of them from simply failing to implant. That means that every time you have unprotected sex and the woman is fertile, there's a 50% chance that you are committing murder. All that "trying to have a baby" stuff? You're a serial killer.

Oh, it gets worse. So much worse. You know what else is alive in a woman's body that has different human DNA? Egg cells. They're alive, and each one is a potential baby. If you're a woman who has a menstrual cycle, once a month your body releases one (at least, could be more; I have fraternal twins) egg cell, which has about 24 hours to live and get fertilized. Every time you ovulate and you don't get pregnant, you've committed murder, at least according to your logic. It was alive, with its own human DNA, and you murdered that "unborn baby".

But of course, it's so much worse for men, because, according to the internet, "A healthy adult male can release between 40 million and 1.2 billion sperm cells in a single ejaculation." Each one is a living thing with its own unique human DNA, and how many will actually end up fertilizing an egg? This isn't murder, it's fucking genocide. Hundreds of millions of "unborn babies" with every single ejaculation.

Is this ridiculous? Yes it is.

Now those of us who are a little more sane about these things say that saying a fertilized egg is a person is like saying throwing a couple eggs with flour and sugar in a bowl is a cake. A cake and a person are both things that start with certain ingredients, but take time and a process in order to be complete. A bag of flour is not a cake. Flour, sugar, and eggs in a bowl is not a cake. Flour, sugar, and eggs mixed together in a cake pan and set in a cold oven is not a cake. That cake pan ten minutes later in a warm oven is still not a cake. It's not a cake until it has spent the full time at the full temperature in the oven and has been taken out. Then, and only then, is it a cake.

So it is with a baby.