This early morning view of the inner wall of Gale Crater is ethereal. (credit: NASA)

People like Elon Musk and others in the “space settlement” camp believe NASA and the US space industry should colonize Mars and make homo sapiens a multi-planet species. Musk wants SpaceX to one day send colonists to Mars, while NASA is talking about building sustainable habitats on the red planet. Even if we overcome the technical and financial challenges that stand in the way of putting humans on Mars, we know precious little about how microgravity and heightened radiation will affect the ability of humans to reproduce in space. Without procreation, there is no permanent colony, and early tests aren’t promising.

But let’s assume SpaceX, or an international coalition led by NASA, or China’s space agency eventually figure out the engineering and financing of a Mars colony. Let’s also assume the biology of reproduction in space, and on foreign worlds, is a solvable problem. After homo sapiens becomes a multi-planet species, the question becomes, would we remain a single species of humanity? Scott Solomon thinks a lot about this question in his new book Future Humans, which will be published by Yale Press in October. In it, he explores the future evolution of our species, including some musings on Mars.

“The general concept for the book is to ask about our ongoing evolution, from the perspective of a scientist who takes what we know about our past, what we know about today, and thinking about the long-term possibilities for our species,” Solomon, a biologist at Rice University in Houston, said. What, he wondered, would it take to lead to development of a new species? Put another way, how long would humans on Mars remain human?