In sci-fi, we can find the concept of artificial fertilization and incubator quite commonly. I work in a company that's heavily involved in that technology, so I became curious to adapt this to my medieval Europe-inspired fantasy world as some magical force. It could be some sacred tree that a couple can spill some of their blood into the sap and the tree will offer an egg-like fruit that a baby will eventually break out of. Or maybe even the old tales of birds carrying the couple's baby from somewhere. The mechanism doesn't matter at the moment. What I'm interested in is the effect that such a means of reproduction that doesn't involve 10 months of pregnancy will have to the population and society.
Let's lay down some assumptions first:
- The mechanism has practically unlimited capacity, but won't allow a couple to use it too often.
- The baby is the biological offspring of the couple and the couple has no control whatsoever to the traits the baby will have, just like conventional reproduction.
- Inter-species offspring is also possible (like half-elves), but only if the couple is biologically similar enough. Obviously, a homosexual couple can also have a baby this way.
- Perhaps the mechanism will do some tweaking to prevent genetic diseases, which could be an added bonus to using the system. This also means a baby boy from two females is also possible.
- The baby is delivered much faster than conventional reproduction.
- There are no concerns like "can we really say this is our baby even though we didn't birth it?" or "does such a baby qualify as human?" at all.
- The world visually resembles medieval Europe, but assume a utopia in terms of human rights, equality, protection of the weak, etc.
- Abusing the mechanism to mass-produce humans for slavery, war, etc is not possible, nor would anyone think of attempting it even if it was.
Now, I'm looking to build a world where this mechanism has been in place for a long time since before history, rather than trying to imagine how the world would react to its sudden discovery. What would population growth and maintenance in a world where this mechanism is common look like? Of course, traditional pregnancy still exists.
I think it's obvious that the biggest difference would be when a rapid increase in population is required, such as at the early stages of a settlement's growth, or right after a big drop in population due to some calamity. But in normal periods, how would families be in the presence of such a reproductory mechanism?
Update: one thing I'd forgotten about is the production of breast milk, which requires pregnancy. Alternatives to natural milk would be in demand, creating interesting ideas for the economy and industry in the world. Although males being milk producers is an idea I'm willing to probe.
Update 2: I originally wasn't going to bring this up because it's my fault for making this question too vague and I didn't want to stop people from exploring a lot of possibilities based on the core concept (such as JBH who brought up wonderful points) regardless of whether it fits my intentions, but I noticed that too many answers are actually restricting themselves to the tree example and the interpretation that anyone can make a baby anyhow out of any people. I'm still not trying to stop anyone from exploring under that assumption so I won't update the above points but I will clarify this: I failed to list the fundamental assumption that two people must intend to use the mechanism with the specific wish of having a baby between them and full understanding of what they're doing. Which is evidently a very big communication mistake on my part because I was just thinking as a biotech worker. Too late to point it out I guess. I think I will post a separate question that will be closer to my intention in the future, after coming up with a proper mechanism that 1) will be hard or preferably impossible to abuse and 2) is also a difficult process although it has no biological impact to either parent.