We conceive of life on Mars as consisting of strange alien figures, typical science-fiction creatures thriving in the extreme environments of space. But how realistic is this picture, really?
As humanity pushes ever further into space, we have to reckon with the question of what may happen to our children, and their children, in a civilisation based on a planet like Mars.
In search of an answer, the evolutionary biologist Scott Solomon has looked at the process of how humans evolve, to build a picture of how living on a planet like Mars may shape the way we evolve as a species.
More on human spaceflight
In his book, Becoming Martian, he speaks to astronauts, physicists and biologists to consider the adaptations that the human body makes as it enters space, and how that might impact the survival of our species.
We sat down with him to discuss some of the findings of his research.
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Are humans still evolving on Earth?
We are. Evolution isn’t something you can easily turn off.
It’s tempting to imagine that we have created so much technology, and so successfully buffered ourselves from the natural world, that we are immune to evolution. The reality is that we are not.
We can even see from the COVID-19 pandemic that we are still at the mercy of nature.
From COVID, we learned that some people are more predisposed to severe disease than others and we’re still figuring out what factors are at play to cause this.
We’re mostly familiar with the concept of natural selection – ‘survival of the fittest’ – but there are many evolutionary mechanisms.
For example, we can think about gene flow, which is the movement of individuals and their genes back and forth between different populations.
And, of course, gene mutation is an important part of evolution. Every human baby that is born has, on average, 60 mutations in the part of its genome that produces a function.
Despite declining fertility rates, there are more babies being born now than ever before, and so we have more mutations and greater genetic potential than ever to adapt to the changing world we’re living in.
Is it realistic that regular human space travel will start to happen?
In some ways, we’re already there. The Artemis II mission took humans into the Moon’s orbit for the first time in 54 years – further from Earth than any humans have ever gone before.
Think of the missions that don’t necessarily require teams entirely made of professional astronauts: Blue Origin, SpaceX or Virgin Galactic.
It’s likely that this type of mission is only going to increase, and a lot of the technology to achieve this travel already exists.
In the short term, I would expect this would focus on travel to low-Earth orbit, or brief up-and-down rocket trips called sub-orbital hops.
I think furthering our reach into space, to the Moon and then Mars, is the next step we will take.
What happens to the body when we lift off into space?
The first thing that happens is the body experiences high G-force during liftoff. You go from zero to as much as around 28,000 km/h (17,500 mph) very rapidly.
Essentially, you feel much heavier than normal, and then you transition rapidly to the weightlessness of being in orbit.
A lot of people experience motion sickness in this process.
The longer you spend in a weightless environment, the more changes your body experiences. All the fluid in the body becomes distributed more equally.
On Earth, more of our fluid is in our legs because of Earth’s gravity and the heart has to pump blood upwards to the brain.
Not so in space: astronauts often look puffy faced in weightless environments because there’s more fluid in the head.
They also sometimes use the term ‘chicken legs’ to describe the effect of having less fluid in the legs.
Over longer periods of time, the muscles start to weaken, particularly in the lower body and the back.
You don’t use your lower body muscles so much. As our bones respond to muscles, the bones also weaken too, losing density.
How might a human being growing up in this environment evolve differently?
This is one of the main topics of my book Becoming Martian.
In science fiction, authors often depict aliens as being long and thin because of reduced gravity.
Mars, for example, has three-eighths the gravity of Earth, so about a third of the gravitational pull.
Although we don’t know exactly what happens to humans in this environment beyond simulate spaceflight, we assume it’s something like the effects of weightlessness.
If a child is born on Mars, with the genetics of an earthling, they will lose bone density throughout their life.
It also means a woman born on Mars giving birth to a child is going to experience dangerous forces if her bones are weakened.
Over time, this might mean that those with denser bones have a higher chance of surviving childbirth, so actually Martians may evolve to be the opposite of the long, thin people science fiction suggests.
We have to remember that evolution is all about making babies, and anything that improves our ability to reproduce will become more common over generations.
What kind of research can we do to figure out what happens to us in space?
People are researching this problem in all kinds of ways. At the NASA Space Radiation Lab, they have a galactic cosmic ray simulator.
It’s a particle accelerator with a target room where a biological sample can be placed, like cells in a petri dish or an animal subject.
Their exposure to simulated space radiation can tell us how humans might be affected by galactic cosmic rays.
Another fascinating part of the puzzle is at NASA’s microbiology laboratory at Johnson Space Centre, where researchers look at microorganisms like bacteria on the International Space Station.
These organisms evolve much faster than we do. Understanding them will be essential if we ever establish a long-term presence in space because we bring microbes with us everywhere we go.
Bacteria that travel to space on our bodies may tell us something about evolution on a much shorter timescale in space; it might also form new, potent pathogens that we have to protect ourselves against.
Can we modify our bodies to cope with spaceflight?
One of the ways we might safely approach long-term space travel is to modify people’s bodies, their genetics, to make space a safer place for them.
The limiting factor is knowing what genetic changes to make and how safe these changes are.
There are, of course, also major ethical considerations. Many of the unanswered questions about our ability to thrive beyond Earth boil down to ethical questions, beyond the serious technological limitations and biological practicality.
My take-home message is: let’s make sure we understand what we’re setting ourselves up for.
Is it ethical for humans to go into space on one-way missions?
Knowing what we know, I think travelling to space shousld proceed with caution but we shouldn’t push for long-term space settlement just yet.
It’s not that we should never do it. Right now, however, we don’t know what would happen to future generations; we don’t know if human reproduction is even possible away from Earth.
There are too many variables, and most of what we know is based on a very narrow slice of humanity: mostly healthy, mostly white and mostly male.
We also don’t know if a child born on Mars would ever be able to come back to Earth – it may not be safe for them.
I hope that we can get answers to those questions before undertaking a one-way journey into the extreme environment of space.
