At the beginning of the 1970s, when literary science fiction was as interested in breaking taboos as in breaking the surly bonds of Earth, Kurt Vonnegut wrote a story about a rocket loaded with enough freeze-dried sperm to inseminate the Andromeda galaxy. "The Big Space Fuck" was not the subtlest of satires. But its central conceit did at least nod to the idea that sperm—and, presumably, eggs—have some sort of role in securing a human future, even if all the characters in the story do end up being eaten by giant mutant lampreys.
Would that all space visionaries were as up-front about the facts of life. There has recently been a new wave of speculation and hype about the possibility of human habitats beyond the Earth. The Mars One foundation is talking about establishing a colony on Mars in the 2020s; Elon Musk, the entrepreneur behind the rocket company SpaceX, says he dreams of making a similar voyage himself, though not quite yet; Eric Anderson, chairman of a company that puts paying customers on to the International Space Station and founder of another which aims to mine asteroids, recently told the journalist James Fallows that he expects "irreversible human migration to a permanent space colony" within three to six decades—that is, in a time as close or closer to today as today is to the launch of Sputnik in 1957.
Not all of this is as technologically nutty as it sounds. Mars One’s notion that it could put together human interplanetary missions in ten years, with the cash generated by selling media rights, is prima facie absurd. The idea that Musk (42 this June) could be in a position to take a trip to Mars in his later years is more plausible; SpaceX has demonstrated an impressive ability to lower the costs of spaceflight, and might well be able to extend its capabilities too.
The nuttiness comes when you start talking colonies. Any "irreversible settlement" needs more than freeze-dried sperm. It needs babies. In the early 1960s Arthur C. Clarke—after whom the jizzship in Vonnegut’s story is named—wrote a short story of his own entitled, more decorously, "Out of the cradle, endlessly orbiting". The title is a tribute both to Walt Whitman and Konstantin Tsiolkovsky, the visionary who established the dream of a cosmic destiny in the Russian imagination with gnomic utterances such as "the Earth is the cradle of the mind, but one cannot stay in the cradle for ever". The sting of the story comes with the unexpected cry of the first baby born beyond the Earth, a cry more powerful to the protagonist than the roar of any rocketship.
At the moment that cry is no nearer being heard than it was in 1962. There is no evidence that people can have healthy babies—or, for that matter, any babies—away from Earth. The role that the Earth’s gravity plays in human pregnancy is unknown, but the chances that it is limited to encouraging backache seem remote. And evolution had no cause to optimise the process for other gravities, and when evolution doesn’t need to do something, it tends not to bother. Full-grown humans spending time in orbit, where they experience what’s known as "microgravity", undergo a number of changes with quite serious medical consequences, such as muscle wasting, brittle bones and changes in pressure within their eyes. Some of this can be avoided with exercise and appropriately constrictive hosiery. Neither prophylactic is much use in utero, where making bones and balancing fluid pressures matter quite a lot.
What do animal studies reveal about the problem? Not much. Though humans have had rudimentary space stations since the 1970s, they have not been used to rear little microgravity-born mammals. Plans to install a centrifuge on the International Space Station which would have allowed long-term studies of life under Martian gravity as well as in microgravity came to naught. If you think this shows a lack of interest in permanent space colonies among those who have been paying for research in orbit, you could be right.
The would-be colonists may feel that when they turn their minds to solving such problems, solved they will be (there are plenty of rocket scientists on tap, after all). If so, they could be in for a shock—there is no guarantee that a way can be found for pregnancy to work off the Earth without, at the very least, the sort of experiments from which people would rightly blanch. But it seems more likely that they are not thinking much about the problem at all.
As Vonnegut was scabrously saying, fantasies of space travel are not, for the most part, fantasies about expanding the seamless human world of life and love which has, until now, had no option but to be Earth-bound. They tend towards something colder: fantasies about leaving the world behind, or starting it anew on the other side of the sky. They are ways of thinking about the future as something less like a birth than a death—which is, after all, the oldest established way out of one world and into another. Indeed, much of the humans-in-space enthusiasm around at the moment is about one-way trips, such as those touted by Mars One. There is an undeniable, if somewhat self-indulgent, romance to such ideas of radical sundering—but no obvious place for babies.