Becoming Martian: How Space Settlement Could Reshape Human Evolution

As the ambition to establish human settlements beyond Earth gains momentum, a critical question arises: what impact will life on another planet have on our remarkably biology? The challenges of adapting to environments like Mars aren’t merely logistical; they could trigger fundamental evolutionary changes in the human body and mind. Scott Solomon, a teaching professor of biosciences at Rice University, explores these potential transformations in his new book, “Becoming Martian: How Living in Space Will Change Our Bodies and Minds” (MIT Press, 2026).

The Evolutionary Imperative

Solomon argues that evolution has meticulously shaped humans to thrive on Earth. Our bodies and brains are adapted to Earth’s atmosphere, gravity, radiation levels, microbial ecosystems, and light-dark cycles. From bone density to the circadian clock, these traits are the result of millions of years of adaptation to our planet. Permanent life on Mars, however, would necessitate adaptation through different evolutionary pathways.

Challenges of the Martian Environment

Settlers on Mars will face a unique set of challenges, including significantly reduced gravity (38% of Earth’s), increased exposure to radiation, and a lack of the diverse microbial ecosystems that contribute to a healthy human immune system. These conditions could lead to transformative changes over generations. As Solomon explained to IFLScience, “Animals on islands often get bigger or smaller over time. It’s possible this could happen to us.”

Potential Physiological Changes

• Weaker Bones and Muscles: Reduced gravity, similar to the effects observed on the International Space Station, could lead to bone density loss and muscle atrophy. This poses a particular risk to children whose skeletal and muscular systems are still developing. Solomon notes, “If you build your skeleton and muscles in a low-gravity environment, there’s a chance your skeleton and muscles won’t build in the right way.”
• Larger Head Size: Solomon suggests that births on Mars are likely to occur via Caesarean section. If this becomes the norm, the evolutionary constraint of head size being limited by the birth canal would be removed. This could potentially lead to the evolution of larger brains and head sizes.
• Altered Skin Pigmentation: Mars lacks a global magnetic field and has a thin atmosphere, resulting in higher radiation levels than Earth. This could drive the evolution of increased melanin production for greater UV protection, or even the emergence of new pigments, potentially altering skin color.
• Compromised Immune Systems: Astronauts in space experience weakened immune systems, and the microbes that travel with them evolve to adapt to new environments. Children born in extraterrestrial environments would develop immune systems with limited exposure to microbial diversity, potentially making them more susceptible to illness.

The Microbial Threat

Solomon emphasizes that the microbial threat is often underestimated. The limited microbial exposure in space settlements could significantly impact the development of robust immune systems, potentially hindering the ability of humans to travel freely between planets.

Are We Ready to Become Martians?

Considering these potential challenges, Solomon concludes that humanity is not yet fully prepared for space settlement. “I’m not saying we shouldn’t go. In fact, I think ultimately there are great reasons to attempt, but I don’t think we’re ready,” he stated.

About Scott Solomon

Scott Solomon is a biologist, professor, and science communicator at Rice University. He is the author of “Becoming Martian” and “Future Humans: Inside the Science of Our Continuing Evolution.” He also hosts the podcast “Wild World with Scott Solomon.” He is a Research Associate at the Smithsonian Institution’s National Museum of Natural History and a Fellow of The Explorers Club.

Sources:

• Rice University News
• Scott E. Solomon, Ph.D. – Rice University
• Rice Space Institute
• MIT Press