Martian Society

The first Martians were colonists from Earth, weary from long months of travel. They were scientists and explorers, religionists of every stripe, from Jainists to Mormons to born-again Christians (all of whom shunned the alcohol preferred by their fellows for surviving in a hostile land, but who still attended local honky-tonks for the company of their compatriots). The third planet sent their best and brightest, but that only ever resulted in long-term distress, as the first settlers treated the new Martians poorly. The distance between the third and fourth planets was vast, and Earth ruled the Red Planet as a colony. War might have been inevitable, and came within a hair’s breadth of happening a few times, but The United Nations invoked the breakaway province rule.
Freed from the mother world, Mars grew into a regional power, and eventually Earth’s only true rival in the Sol system. Mars’ lighter gravity caused minute but defined changes to human physiology over hundreds of years, much like the Belters, who were shaped by living in microgravity. Natural selection and lesser gravity mean Martians have less muscle mass and bone density compared to Earthers, leaving them slender and taller than Earth norms, though not unusually so—hormone treatments are widely available most on Mars. Blood oxygen boosters, muscle fatigue inhibitors, and bone density enhancers allow Martians to tolerate even Earth, albeit with physical discomfort at the gravity and emotional discomfort at the barely disguised glee of United Nations diplomats. Martian selection pressures have favored those with better tolerances for low oxygen environments, however, and Martians use slightly less oxygen on average than other humans in the Sol system.