BECOMING MARTIAN

Pondering otherworldly questions.

Humanity may choose to go to Mars in the near future. But a permanent presence there would likely lead to some notable characteristics among the red planet’s residents, writes Solomon, an evolutionary biologist at Rice University. Travel to other planets, that staple of science fiction, is also a dream for those concerned that our species is vulnerable to extinction—through war, environmental catastrophe, asteroid impact, or, billions of years from now, the sun dying. To ensure our continued existence, some believe we must leave our home planet. But there’s a catch. Different populations of a single species stranded on separate islands can eventually split into two species. Solomon extends that idea to space islands: planets. Inevitably, in a large enough reproducing human group, the demands of living on Mars would mold the descendants of people who went there into a new species of human. Back-and-forth travel could prevent speciation, but may be impossible due to Mars’ much lower gravity. In his foreword, astronaut Scott Kelly writes, “Returning to Earth’s gravity after my missions was among the most physically demanding experiences of my life. Could a person who’s never experienced Earth’s gravity handle it?” The Martian environment could modify humans to have denser, shorter bones, orange skin for radiation protection, immune systems tuned only to the limited challenges of the distant colony, and numerous other adaptations, some behavioral—to minimize any disastrous conflicts, settlers may need to be unusually easygoing. Spacefarers might even be genetically modified in advance to increase their odds of success. “It’s an irony of cosmic proportions,” Solomon writes in this deeply researched and engaging work. “By preserving ourselves we ensure that we will never be the same.”

A fascinating combination of space science, genetics, and evolutionary biology.