Part of my series on countering misconceptions in space journalism.
Space development advocates routinely envision cities in space or on other planets, which implies the eventual existence of humans born off the Earth. For some reason this topic is surprisingly divisive, so I feel compelled to add my voice to the noise.
The concern is that humans may be unable to reproduce in a weightless, or reduced gravity environment. For example, the surface of the Moon is 1/6 g, while Mars is about 3/8 g. Both are a lot of fun if you can get time in a vomit comet!
For me, this concern doesn’t make it onto my list of short term worries, because babies are the least effective way to get humans where you need them. Space stations, Moon bases and Mars cities will need lots of highly trained humans to do all kinds of complicated work, and will suffer a terrible labor shortage. Humans below a certain age are enormous net consumers of labor, so reproduction will be a niche issue at best. In any case, it won’t be on the critical path.
This isn’t that crazy to say. We routinely deploy professional specialists across the world when we need people to operate submarines, oil rigs, or Antarctic stations. No-one ever suggested that the key to operating a mine efficiently is to produce the workers on site, with a 20 year operational delay. And since the automation of factories and mines, children have generally been discouraged from working in these environments. Indeed, migration, or human importation, has driven population growth in many countries, such as my native Australia, for the entirety of their modern existence.
So, in the short term, whether or not humans can breed in space is not really a critical problem. But what about the long term? Earth can produce plenty of humans for the Moon or Mars, but what about interstellar voyages? What about after industrial self sufficiency and post-scarcity luxury space communism is achieved? All these things may occur way before evolutionary changes could significantly alter our genome.
The second reason I’m fundamentally unconcerned by this question is that, as of 2020, we simply have no evidence at all, one way or the other, of fertility in reduced gravity. Some space station experiments have suggested problems with zero g, but not conclusively.
We know that tiny environmental changes (or nothing at all) can end the viability of a fetus. On the other hand, all aquatic species live and reproduce in an environment of neutral buoyancy. Babies are conceived and grow in a watery environment with plenty of external forces, bumps, and bounces, but no overarching orientation. An expecting mother can perform yoga, take sea voyages, swim, or lie down without the baby being harmed in any way. Personally, I think we’ll find that conception and gestation work fine in Mars or Moon gravity. Interestingly, there are animal experiments on the ISS that may eventually inform this question.
But let’s say that it turns out that humans are 100% infertile in any environment except one g, and that this has become a big problem for parents wanting children on Mars or the Moon. There is a mechanically easy fix. A maternity hotel built as a centrifuge with a truncated inverted cone floor plan can readily reproduce 1 g, or any other desired apparent gravitational force. There’s no reason why this futuristic form of maternal confinement should be cramped – any civilization capable of building a city big enough to have encountered this problem will easily have the resources to build an enormous rotating hab with generous interior spaces. Space radiation similarly.
Technologically, it’s on the level of an advanced theme park ride. Compared to replicating the industrial stack on a barren world, it’s a very nice problem to have.