Gravity Molded Human Consciousness—But a Future in Space Could Make It Evolve, Scientists Say

6 min readHere’s what you’ll learn when you read this story:The near-absence of gravity during space missions can temporarily alter astronauts’ bodies and brains. In one experiment, gene expression and chromosomal telomere length changed.Some scientists theorize that long-term life in microgravity could reshape human cognition, potentially even consciousness, and other aspects of human evolution.Evidence for such future changes is limited for now. But researchers are looking for ways to predict how humans might adapt to long periods in space.In 2016, NASA astronaut Scott Kelly returned to Earth after 340 continuous days aboard the International Space Station (ISS). He readapted to our gravity in months, but in the meantime, researchers observed some temporary alterations in his body. Compared with his earthbound twin, some of Kelly’s telomeres, which act as protection devices for chromosomes and are markers for aging, had lengthened while he was in space; they shortened again back on Earth. And his gene expression—which is the way genes are turned “on” or “off”—had changed significantly.It’s apparent that spaceflight can induce some unexpected biological modifications in astronauts.However, researchers looking ahead to longer-term space travel are considering the possibility that such endeavors could actually transform us as a species. But could it truly make us evolve? After all, humans have continued evolving even in the recent past according to the demands of their environment, such as Tibetan people who have adapted genetically to live in low-oxygen, high-altitude environments.One researcher argues that once humans let go of gravity, it might change the brains of future generations. Research recently published in Frontiers in Psychology argues that gravity on Earth, as a stable presence throughout human evolution, affects how our brains organize themselves. Gravity “is incorporated into the internal models the brain uses to regulate perception, movement, bodily orientation and interaction with the environment,” says co-author Elisa Raffaella Ferrè, PhD, a professor of cognitive neuroscience at Birkbeck, University of London.Yet, this research is a theory-driven piece that requires more experimental protocols and statistical analysis for confirmation, she says. “The paper synthesizes findings from existing behavioral, neurophysiological and neuroimaging research on altered gravity and uses these findings to develop a theoretical framework.”When humans leave gravity for microgravity environments such as space, “the brain is confronted with a very different set of sensory statistics,” Raffaella Ferrè says. That’s true in the short-term sense, as “vomit comet flights” used for astronaut training can induce confusion about how to move, and how to coordinate your hands and limbs—even in 30-second simulations of microgravity, as the plane dives down and then back up again.But what Raffaella Ferrè is more interested in is longer-duration space missions of months and years. “The main contribution of the paper is therefore conceptual rather than empirical,” she cautions, but “we propose that altered gravity could potentially modify aspects of consciousness.”She says you can draw a light analogy with a psychedelic state, while clarifying that psychedelics and space are not in any way equivalent in biology or otherwise. But such states, she says, can change how the brain makes predictions and, in turn, give “greater flexibility in neural representations,” or the ways in which brain networks connect.For example, in a different peer-reviewed study of space simulations that Raffaella Ferrè also co-authored, researchers analyzed 15 studies and 377 participants who participated in analogs such as lengthy bed rests or vomit-comet flights. The study in which Raffaella Ferrè participated suggested that the brain can change in regions that are linked with spatial orientation, sensorimotor functions, and balance. In other words, that “altered gravity may change the neural systems involved in consciousness,” Raffaella Ferrè says, through “recalibration of internal models that the brain uses to predict the effects of gravity on perception and movement.”Yet it is difficult, cautions Jerome Carriot, PhD, a physiology research associate at Canada’s McGill University, to validate theoretical altered states with more research-backed experiments when it comes to areas like microgravity’s effect on the vestibular (balance) system. Carriot, a veteran vomit-comet flyer, notes he “personally experienced hundreds of parabolas and have never felt anything resembling a psychedelic state—although brief periods of microgravity are obviously different from spending months in orbit,” he says.Carriot allows that a partial parallel can be drawn with something like loss of vision; when we lose a key sense like sight, the brain is capable of reorganizing and responding “more strongly” to other inputs, like sound. “However,” he adds, “such cross-modal plasticity does not by itself imply a psychedelic effect or a change in one’s level of consciousness. The claim that microgravity produces psychedelic-like or transformative consciousness therefore remains speculative and has not been directly demonstrated.”There’s an inherent, larger problem in confirming any of this research in space: only so many people have flown there. More than 700 people have gone above the Kármán line, or the 60-mile (100-kilometer) altitude threshold considered internationally to be the boundary of space. But most of them have participated in short-term missions (some as short as a few minutes), aside from longer stays on a few space stations. And while NASA says that nearly 300 of those people visited the ISS, for example, not all of them were long-haulers; as of March 2020, for example, the ISS only had 170 individuals who stayed between 48 and 340 days each. Only a few more people have joined since then. When you look beyond Earth orbit, the ranks thin further: not only were the missions short (no more than two weeks, generally) but only 28 people have ventured to the moon—and all but one of those astronauts were male.Statistical validity needs numbers and repeatability. In such a small population that is hard to achieve. But Kelly, who participated in a nearly one-year mission on ISS, has said one thing is for sure: cognition needs to stay sharp. “Perhaps the most dangerous symptom is impairment to cognitive function—we have to be able to perform tasks that require a high degree of concentration and attention to detail at a moment’s notice, and in an emergency, which can happen anytime, we need to be able to do those tasks right at the first time,” he wrote in his memoir, Endurance. “Losing just a fraction of our ability to focus, make calculations, or solve problems could cost our lives.”So is there a difference in cognition across a long-term spaceflight? Authors of a long-running cognition study on the ISS found “no systematic decline in cognitive performance during six-month low-Earth-orbit missions” among 25 professional astronauts, the largest sample to date. That finding, published in Frontiers in Physiology in 2024, contradicted previously reported “declines across several cognitive domains during flight and post-flight mission phases,” which the authors said requires more study; changes in cognitive performance could be due to individual changes, or perhaps effects on the brain build up over time, or something else.To speak even more speculatively, sci-fi stories, such as The Expanse, sometimes do portray human bodies physically changing over generations of spaceflight, such as developing spindly limbs. This notion has also been explored a little, from a theoretical point of view, in peer-reviewed literature such as this 2024 American Journal of Human Biology paper looking at the human biology of spaceflight.Some of the paper’s theoretical territory is a thought experiment, building on evolutionary human biology, “to scaffold how we should be thinking about adaptation to spaceflight environments, including possible field-methods that could [or] should be used” for experimentation, says lead author Mallika Sarma, PhD, an assistant professor in anthropology at the University of Pennsylvania.Moving from empirical research to sci-fi, Sarma thinks that after lots of time in space, we could see changes in the human body “to a point”; for example, humans would be unlikely to “regrow a tail,” she says. “In populations that live in extreme cold, we still do see some distinct behavioral [and] physiological adaptations,” for example. However, we might be able to counter the problems of lengthy microgravity stays by creating gravity systems, she adds, just like humans use warm coats now to stay healthy in the cold.“All that is to say that adaptation is both complex and complicated and super cool,” Sarma says. “Unless you have a firm sense of the environment, and it is either extremely stable or you can anticipate every possible change, anything beyond a single generation is very difficult [to predict].”So how could the human body and brain change in space? We can’t say for sure yet, as so few people have flown there. But it’s fun to imagine what could happen. It might also be useful to consider those thought experiments as a framework for asking the right questions when it’s time for the next generation of “life in space” experiments.Elizabeth Howell (Ph.D., she/her) is one of a few space journalists in Canada. She has written five books, and was Space.com's former staff reporter in spaceflight. As a freelancer, she has written or edited articles about astronomy and space exploration for outlets such as Payload Space, Air&Space Magazine, Sky & Telescope and Salon. Elizabeth holds university degrees in journalism, science and history and also teaches an astronomy course, with Indigenous content, at Canada's Algonquin College. Aside from watching several astronaut missions launching from Florida and Kazakhstan, Elizabeth once lived like an astronaut at the Mars Society's Mars Desert Research Station in Utah.