How mysterious must conception be when you don't have a microscope that lets you get a good look at the process? You know that it has to do with a penis in a vagina - that much is pretty certain - but what about from there? It has something to do with semen, you can make that basic assumption, but how does that sticky goo lead to a baby in nine months? It doesn't make a lot of sense.
Thankfully Pythagoras had some ideas about it, and he was one of the early leaders of the school of thought called preformationism, which said that all living things must always be the same form they end up as, a thought process that eventually led people to come to the conclusion that there were tiny people inside your semen. Little human forms called the homonculus would be in there (or would be inside a woman's eggs, if you subscribed to William Harvey's 17th century ovist preformationism) waiting to get his tiny ass born.
The idea that your sperm contains humans and that wantonly throwing it everyplace is immoral is reflected all the way back in Genesis, with the sad story of Onan. Onan's brother Er (his name, not a speech tic) got killed by God, as would happen back in those days. Onan's dad, Judah, gave him an order - knock up Er's wife, Tamar, so that the bloodline could continue. But Onan had other plans. Here's what the Bible says:
But Onan knew that the child would not be his; so whenever he slept with his brother’s wife, he spilled his semen on the ground to keep from providing offspring for his brother. What he did was wicked in the Lord’s sight; so the Lord put him to death also.
That's a tough Lord. Onan lives on, of course, because 'onanism' has come to mean masturbation. Fame by any means, I guess. But you see how serious God took the whole thing - wasting his spunk was enough to get Onan knocked off.
Back to the scientists. Shit got really weird with Antonie van Leeuwenhoek (I definitely cut and pasted that), the father of microbiology. This guy was a pretty major figure in the history of science, and his work with a microscope was ground-breaking. He was the first human being to see bacteria. He was the first human being to see the banded pattern of muscle tissue. And he was the first guy to ever see a spermatazoa. Leeuwenhoek really loved looking at stuff under his microscope - he looked at cum and he looked at coffee beans and he looked at everything in between.
What Leeuwenhoek saw in that sperm blew a load in his mind. He see all kinds of complex stuff, which he assumed must be the veins and everything we have as humans. It just made sense to him. He saw "all manner of great and small vessels, so various and so numerous that I do not doubt that they be nerves, arteries and veins...And when I saw them, I felt convinced that, in no full grown body, are there any vessels which may not be found likewise in semen." So he figured there was a brain in semen. And, I guess, semen. Semen in semen. Yo dog, I heard you like semen*...
There had been a bunch of ovist preformationists, but these discoveries really made it clear that the homonculus lived in your balls. In fact Nicolaas Hartsoeker straight up saw tiny little people curled up inside sperm. His wacked out illustrations of what he saw appear above. Imagine if your balls were really just a collection of The Matrix-like pods, filled with dormant people waiting to get flung through your urethra.
But that in and of itself created theologicial problems, because it soon became clear that there were a BUNCH of sperm in your semen. Maybe you'd create twins, but what about all the rest of the dudes? This seemed weird and capricious of God, to send so many preformed humans to their death. From this arose panspermism, the idea that maybe all of these sperm get out into the wild and eventually create life elsewhere. It's not a good theory.
All of this fell apart as we were better able to understand biology, and as we were better able to get a look at the process of conception and gestation. Thanks to the geniuses in Monty Python we will always be able to remember these silly beliefs about spooge:
It's easy to believe that these sorts of backwards beliefs are behind us, but the recent Hobby Lobby Supreme Court ruling proves otherwise. Basically the religious goofballs who run Hobby Lobby don't want to allow employees to use their health insurance (into which employees pay every check, by the way) for emergency contraceptives like Plan B and Ella. All of this comes from a huge misunderstanding of science (religious people not understanding science? HOLD ON A MOMENT) because these emergency contraceptives aren't abortion pills. They're not considered abortifacients, no matter how many people on conservative Twitter claim otherwise. Medically they're contraceptives, and they have a very limited window during which they work. Ella, for example. must be taken within five days of intercourse.
This means these people believe life begins the second insemination happens, a stance that is profoundly hard to back up medically (and when I say profoundly hard, I mean you really can't). At any rate, these emergency contraceptives stop the egg from getting fertilized in the first place (fertilization can happen up to THREE DAYS after unprotected sex), so it's hard to see how this would be an abortifacient, which basically means a substance that causes miscarriage.**
And so we're right back at these preformationist guys, who think that the sperm itself is the life. Because there's no other argument against something like Plan B, which stops fertilization itself (and perhaps stops the implantation of a fertilized egg, but that's not totally clear).
One last thing about when life begins: the Bible actually has a passage in Leviticus that explains how much human beings are worth. God tells Moses the actual dollar value of human beings. Women, of course, keep coming in at half the value of men. Here's the passage. Let's see if you notice something:
The Lord said to Moses, “Speak to the Israelites and say to them: ‘If anyone makes a special vow to dedicate a person to the Lord by giving the equivalent value, set the value of a male between the ages of twenty and sixty at fifty shekels of silver, according to the sanctuary shekel; for a female, set her value at thirty shekels; for a person between the ages of five and twenty, set the value of a male at twenty shekels[d] and of a female at ten shekels; for a person between one month and five years, set the value of a male at five shekels of silver and that of a female at three shekels of silver; for a person sixty years old or more, set the value of a male at fifteen shekels and of a female at ten shekels.
Yeah, babies under one month old are vaued at nothing. This really makes Onan's punishment seem doubly harsh.
* That's a joke, but philosopher Nicholas Malebranche put forth the idea that embryos could contain embryos that contain embryos, on for infinity. I contain multitudes indeed. Malebranche actually advocated that everything that lives and that ever will live has been here since the creation of the world, waiting their turn to be unleashed from the seed.
** Abortifacients have been around forever. One Greek colony had a thriving business in growing and exporting silphium, an abortifacient. Such a thriving business they put the plant on their coins.