A.) The body
-- Genetic modification. By the future envisioned in 2312, it seems that the human genome has become more of a suggestion than a hard code. Swan herself has apparently numerous modifications to her brain, and it seems the majority of the body is malleable either through this direct modification, or circumstantial influence like differing gravity in asteroids or on terraformed planets or biospheres.
-- Cybernetics. Swan also has a qube implanted in her head, and it seems this may have been common, if not slightly taboo, as of several years before the beginning of the story. Each qube seems to link directly into one’s senses and can perform many various tasks from calculations to movement tracking, coordination, and even recording its human’s experiences.
B.) The landscape
-- Terraforming. By 2312, it seems Mars has been completely terraformed and Venus is being eyed as the next candidate. The concept of terraforming is such a lofty dream in most near-future science fiction that actually managing to turn a planet like Mars, currently desolate and totally unlivable, into a reflection of Earth, would be such a monumental triumph that it would redefine the history of the universe.
-- Ascensions. Asteroid habitats designed by those like Swan are used (to questionable ethical effect) to experiment with different combinations of plant and animal life, creating entirely unique biomes which never existed—and never could have existed—on Earth.
-- Ascensions, again. Their existence proves further that humanity has gained unprecedented control over the formation and progression of life. To that note, some asteroid biomes are apparently used only for preservation of what was lost on Earth, doing so only where it was possible to save in the greater Solar System what was ruined there.
-- Genetic modification. Again. It seems that through scientific advancements, humanity has not only learned how to alter itself on a biological level, but to prolong its own life and create extremophile individuals capable of withstanding harsher conditions and greater punishment than we in the present might. For example, those on Mercury who, with the aid of technology, can survive standing in direct sunlight which would prove
D.) The community/collective
-- Terminator. The city that slides upon rails over the surface of Mercury, a tiny biosphere dome community kept vibrant and lively on a molten planet only by the collective effort of its residents. When the city is ultimately doomed by the destruction of its rails, it seems it is evacuated in its entirety within a matter of moments.
-- The Mondragon Accord itself. While it seems Earth and its affiliations in space are still gripped tightly in suffocating capitalist systems, those who have escaped them, like Mars, take more socialistic approaches to maintain their populations.
2. Though it seems we’re still a little early in the plot, it’s difficult to imagine its raw material concerning anything other than the conflicts of public and private, capitalism and the public interest. Earth when compared to the rest of the Solar System almost acts like a foil character to a group of protagonists, the nightmare origins that the settlers of the planets and moons must try to avoid recreating while having little limitation in doing the very things that led to them. Given that the main secretive plot seems to be something concerning Earth and its affiliations in space causing unsustainability throughout the entire Solar System, particularly the capitalist systems still strangling the planet and its peoples even after decimating its ecosystem, I would struggle to name many possible alternate interpretations sparing major twists in the rest of the book.
A potential alternative, as a few others have pointed out in this forum, might be a direct focus on environmental caretaking and the consequences for failing to do so. Robinson describes on Earth exactly that which is expected in a worst-case climate crisis scenario; high shoreline rise, resulting in the loss of massive swaths of coastal regions including the entirety of Florida and New York City; the loss of Earth’s ice caps and sheets in their entirety, and the decimation of its biosphere except for those species fortunate enough to be uniquely qualified for survival in dramatically altered habitats. It seems the best humanity can do is attempt to reproduce Earth elsewhere, such as on Mars or Venus or in asteroid biomes, but the repeated implication seems to be that even their best collective efforts can still only create echoes of our true origins.