Advances in science, engineering and biotechnology will produce a superhuman in the near future. In my book Chasing Captain America, I explore the theme of biomedical science as an approach to enhance evolution in a direct and targeted way. Captain America stands as a metaphor for the ultimate and deliberate retooling of human biology for a specific purpose. And one of the purposes to which this could be applied is life on a different planet.
We are more familiar with environmental pressures driving changes in biology here on our home planet. The slow adaptive process of natural selection means millennia are required to see meaningful evolutionary changes in a species. Those species that adapt survive, and those that don’t won’t. This is the so-called “survival of the fittest,” long ascribed to Charles Darwin and Alfred Russell Wallace as the centerpiece to the theory of evolution. For the fit to survive, adaptation must occur. This rule applies in space as well as on earth.
Mars has been marked as the next step in the space exploration by humans. It’s not going to be easy; we face challenges with respect to both getting there and surviving once we land. Mars is a harsh place, where we’ll have to deal with changes in gravity and the effects of radiation. We’ll need to evolve and adapt quickly to this new environment. Our strategies around these adaptations have to include long-term thriving in addition to immediate surviving.
We aren’t going to be strutting around the surface of Mars in flip flops and cargo shorts, breathing in terraformed atmosphere for quite some time and probably ever. Those on Mars are, however, going to be living in a reduced gravitational field, will be exposed to high levels of radiation and will need to have excellent optimized oxygen extraction. And to enable all that, we need to pre-evolve folks before they arrive on Mars and begin the process of settling a new world.
In his debut in Captain America Comics no. 1 in March 1941, we see Steve Rogers, “a frail young man” who is “inoculated with the strange seething liquid” by Professor Reinstein. This “super soldier serum” and subsequent “vita-ray treatment” turn the frail army reject into the pinnacle of human performance in the guise of Captain America. While modern science and genetic engineering take us closer to creating Captain America every day, we can’t transform instantly as did Captain America in his origin story. How long might it take for real?
To gauge how fast meaningful change like this might be achieved, Lauren Koch and colleagues at the University of Michigan Medical School selectively bred rats and tested their functional capacity. Animals—including us humans—respond to exercise training with differential adaptations. Breeding rats in pairs based on functional response to exercise training allowed the researchers to create a group of low and high responders.
After 15 generations of selective breeding, high response rats increased their running distance to approximately 220 meters, while low response rats actually got worse, declining to about 65 meters. The “control” rats were, on average, in between at about 140 meters. The results demonstrate very clearly that genetic selection can alter functional characteristics in a relatively short time—but still around 300 years in human terms.
Our species is clearly headed toward colonization of other worlds. This is where contemporary science and Captain America meet the new frontier of life in space. Space travelers will experience microgravity in space and about a third of Earth’s gravity on Mars, changes that raise serious health concerns. Even the physical shape of our cells changes in different gravitational fields. In contortions that are reminiscent of DC’s Plastic Man or Marvel’s “Mr. Fantastic” Reed Richards, cells change from slightly irregular borders to smoothly rounded ones. Our cells have biological scaffolding inside them that give and detect changes in shape, along with entry and exit points in the form of ion channels made from proteins dotted throughout; renovations due to changes in gravity lead to alterations in how they function.
Hearing, balance, vision, the distribution of blood in the body, kidney, urinary and muscle function and bone density are all negatively impacted. The big-picture issue for NASA and other space agencies is the effect that three years in space—roughly the time a return trip to Mars will take and which is three times the current longest space mission—will have on human physiology.
The environment in space is literally alien to human physiology—something that has fascinated astrobiologist Dirk Schulze-Makuch at Washington State University. Schulze-Makuch has published extensively on exobiology and extraterrestrial life both in the scientific literature and in writing for the general public; he’s the author of four popular books and two novels.
Schulze-Makuch believes that if a colony were established on Mars, even taking into account its reduced gravity, we would be able to breed and give birth as we do here on Earth. Over generations of life on Mars we would slowly begin to adapt. Much of that adaptation might be related to the harsh ionizing and ultraviolet radiation that humans would be exposed to. We would gradually, for example, see increased pigmentation—from melanin—in skin exposed to the light on Mars.
Pigmentation would not necessarily shield us from the effects of ionizing radiation, though. A real shield would be needed. Maybe not one made of the mythical metal vibranium, like Captain America’s, but something as effective at deflecting radiation as his is at deflecting bullets. Some microorganisms on earth—like the bacterium Deinococcus radiodurans—use minerals like magnesium and manganese to help protect them from radiation. It can survive being frozen, radiated, dehydrated, placed in a vacuum and exposed to acid. Its superpower is its survivability. It can withstand exposure to more than 5,000 gray of ionizing radiation. A dose of this magnitude causes DNA breakage in other organisms and would be fatal to you or me.
Deinococcus radiodurans is able to survive and resist the effects of radiation because it has rapid DNA repair and multiple copies of its genome. It also has doughnut-shaped DNA strands instead of the double helix we typically find in most organic life on Earth. To give you a sense of how much more radiation a body would be exposed to in space, a year on the International Space Station is equivalent to the radiation exposure from flying between Los Angeles and New York more than 5,000 times.
Repairing damage to DNA is a critical function of our cells. For life to continue, our cells must divide and create a copy of our DNA in each new cell. If the copy is corrupted, the errors will be handed down to the next generation of cells. Errors occur due to mistakes in the process of transcription, and, of particular relevance here, damage is inflicted by ultraviolet and other radiation sources.
When the copying process of your DNA is ongoing, sometimes base pairs get mixed up. It doesn’t happen very frequently, but with the vast number of cells in your body replicating every seven to 15 years, even small errors can cause major problems. We need to keep working to better understand how repairs can be optimized, perhaps borrowing from mechanisms in other animals.
A chimeric approach to creating a hybrid could include tardigrade DNA to withstand radiation. Tardigrades are microscopic animals that look like a cross between a bear and a mole. (Trivia hint: they’re the little animals seen in the “quantum realm” in the 2018 movie “Ant-Man & the Wasp”.) Tardigrades can withstand just about anything—including the extreme radiation exposure that normally denatures DNA. Takekazu Kunieda and his colleagues at the University of Tokyo discovered that a specific protein in the tardigrade helps in this protective role. Kunieda and his collaborators manipulated cultured human cells by inserting tardigrade DNA into them and found they had had a 40 percent greater capacity to withstand x-ray damage than do ordinary human cells.
Mars is our only near-future option as a potential space colony. If we are going to flourish there as a species, we don’t have time to wait for evolution to do its slow but steady work. Much of Schulze-Makuch’s work has looked at hypothesizing how life could exist on other planets, and he admitted it is a “major challenge to take a highly adapted species like ours and place it out of context on a new planet.”
Captain America, himself a product of the ultimate science experiment, is a metaphor pointing to the potential for bioengineering life as we know it. As I argue in Chasing Captain America, we need to consider implementing changes in our species that will enhance our ability to survive and thrive in space. Every day, the science and engineering capacity to make these changes is closer to our grasp and further from the functional biology provided by evolution on Earth.
Konrad Szocik and colleagues from Poland, Brazil and the U.S. speculate about the biological and social challenges of human reproduction on Mars in their 2018 paper in the journal Futures. These scientists conclude that a minimum viable target population on Mars would be 5,000 people. To get to that number means surviving and reproducing on Mars. Szocik and colleagues also suggest, as do I, that that using genetic engineering to modify human biology before and after arrival on the Red Planet is the only way to ensure survivability.
In the same way that Captain America and his colleagues came together to form the Avengers, who make a tactical and strategically sound plan for every mission they undertake, we need to strategically accelerate human evolution and arrive “pre-evolved” for the Martian landscape.