The small, non-representative group of initial colonists will create a genetic bottleneck. Their specific genetic makeup will have an outsized influence on all subsequent generations born on Mars, leading to rapid evolutionary change and reduced overall genetic diversity compared to Earth's population.

Titus uses his sci-fi novel to create an "ethical crucible" for human genetic engineering, forcing readers into a binary choice between extinction and genetic modification. This medium allows for exploring high-stakes scenarios and removing the "edge cases" that often bog down real-world policy discussions.

To normalize the ethically fraught practice of embryo gene editing, startups like Preventive are shifting the narrative from just curing disease to radical cost reduction. They claim editing embryos could cost $5,000, a fraction of the $2 million price tag for current adult gene therapies.

Ideologies that rely on a 'blank slate' view of human nature have made a catastrophic error. As genetic technologies become mainstream, the public is forced to confront the tangible reality of genetic predispositions in their own reproductive choices. This will unravel the blank slate worldview, a cornerstone of some progressive thought.

Fears of a return to 1940s-style eugenics are misplaced when focusing on individual reproductive choices. The critical distinction is between government-forced programs and individuals making informed decisions. Preserving individual autonomy is the key safeguard against the historical horrors of coercive eugenics.

The debate over selecting traits like height or IQ misses the point. These are not the ultimate goals for parents but are proxies for what they truly desire: a happy, healthy, and fulfilling life for their child. This reframes the ethical discussion from trait selection to enabling well-being.

Living in a sterile Martian habitat, colonists would only be exposed to a tiny fraction of Earth's microbes. Their immune systems would be unprepared for Earth's vast microbial diversity, making a return journey potentially fatal. This creates a permanent biological quarantine that would accelerate human speciation.

A human born and raised in Mars's one-third gravity would likely not develop the bone density and muscular strength required to withstand Earth's gravity. The physical stress would be painful and potentially debilitating, effectively trapping them on their home planet for life.

Despite decades of spaceflight, there is almost no research on conception, pregnancy, childbirth, and child development in a low-gravity environment. Our assumption that humans can successfully reproduce off-world is a massive, unverified leap of faith and the single biggest unknown for establishing a permanent settlement.