Ageing slowed, not ended

Since about 2300, ageing can be stopped outright — but only by someone who can pay for unlimited brain renewal. Nobody yet knows how long the renewed will live, because the Escape is under two centuries old. Settlement polities plan for lives of about 300 years under the ration, and the Open Cities for about 150 on average: their rich expect to live indefinitely, while their poor still die of age at 70 or 80. The Mandate rations renewal evenly, as policy rather than right, and plans for lives of about 300 years. The Parishad gives free, equal care to everyone up to 100 and sells it after that, so lives there also average about 150. People in 2497 still die of age; it simply takes far longer, and money and law set the timetable.

How it happened

Why the brain is the bottleneck

The body is cheap to renew; the brain is not. Machines grow organs and make gene therapies in bulk. Renewing a brain means replacing neurons without erasing the person, which requires mapping that one brain at the level of its synapses and computing every replacement. In 2024, mapping a single cubic millimetre of human cortex produced 1.4 petabytes of data; a whole brain is about a million times larger. Each renewal needs a fresh map, because the brain has changed since the last one. Centuries of better scanners have not made it cheap, because the map is the easy part. Standard methods and better tools have cut the cost, but each brain still needs extensive individual verification: every replacement checked in that one living brain, against what the person actually does and remembers. The work that remains is large enough that renewal still competes for licensed bulk compute. This uses compute chips, not industrial controllers (see The hardware distinction, in The Mirror Race).

Bulk compute (large clusters of chips, at the scale needed to train or run a mind) has been capped by law since the Partition, and by treaty between the blocs, so brain renewal competes with everything else for a scarce resource. The brain came last because it is where the person lives: you can replace a human liver, but replacing someone's neurons risks replacing them. The Raised face the same problem when they port to a new core (see One mind, one form). Dying of age in 2497 usually means a brain failing inside a body that still looks young.

• Settlement polities ration it evenly. The ration is sized to what licensed compute allows, and on Earth to what habitat capacity allows: fewer renewals for each person, in return for the right to have children.
• Some cheat. A few Settlement citizens buy illegal compute for extra renewals. Rumours of cheats who have renewed far past the ration and live hidden away are persistent, and probably true. Others buy extra renewals at the Parishad's clinics on the Moon, which Settlement law allows only to those who give up their birth licence. As far as the records show, most sell theirs first; the best clinics check, but cheats may go unnoticed at lesser ones.
• The Parishad sells it. Care is free and equal to 100; after that all of it must be paid for, even body renewal. Its clinics on the Moon sell renewals to anyone who can pay, the best and most expensive anywhere, and the sales help pay for care to 100, though each one still spends the Parishad's capped bulk compute (see The Parishad).

How old is the oldest person?

Brain renewal works only on brains under about 130 biological years, so the first people renewed, in the 2290s–2320s, were born around 2165–2190. Anyone among them who has renewed without a break ever since is about 310–330 in 2497, and no human can be older. The oldest confirmed humans are Open-City and Line magnates from that first generation. In Settlement polities the first renewed reached the end of their ration over the last thirty years, so the people who remember the Settlement being built are nearly gone.

Wend, at about 349, is older than any human; only the Lifeboat's crew, braking unseen at Gliese 876, and a handful of other first-generation Raised rival it. It is one of the very few minds alive that remembers the founding first-hand.

Memory is the next limit. A renewed brain still holds finite memories. The first renewed who are still alive, now past 300, are the first to reach that limit: some have begun to lose their childhoods, and memory therapy is a young field. Wend's memory is still sound.

What it changes

• The long-lived rich. Those who can buy unlimited renewal — Open-City magnates, the Parishad's rich, Line founders, a few cheats — accumulate property and influence across centuries. Settlement polities answered with the Rotation Laws of the 2380s, once the first renewed had held office for decades and inheritance had stalled because nobody died. The laws cap tenure in office at fifty years and time-limit inherited property; the young resent them anyway. The Parishad's rotation law caps office at thirty years but sets no limit on inherited property.
• Death has a horizon. A Settlement citizen knows roughly how many renewals the ration allows. Planning one's last century is becoming a cultural form, now that the first renewed have reached the end of theirs. Letting go early — declining one's remaining renewals — is rare, and a scandal where it happens.
• The deepest inequality. Lifespan divides the Open Cities and the Parishad from the Settlement and the Mandate more than wealth or the right to vote, and within the Open Cities and the Parishad it is the starkest mark of class. Some Settlement citizens emigrate for longer lives, and in the Parishad those who refuse the cut-off at 100 look to the Settlement's 300 years.

Justice under long lives

When people can live for 300 years, a life sentence has no fixed length, and renewal becomes the real lever of punishment.

• The Settlement. Renewal is in the floor, so no court can withhold it and prison never shortens a life. Prisoners keep their ration, Raised prisoners their core care. There is no life sentence; sentences are counted in years, and released prisoners must re-sit the Threshold before they can vote again. Victims live as long as offenders, so grievances last centuries.
• The Mandate. Renewal is policy, not right, so a court can cut it: the shortened term. The convict's ageing resumes, and a heavy sentence lets a 200-year-old age out within a few decades. It is a quiet death penalty the Mandate never has to call one, and dissidents fear it more than prison.
• The Open Cities. Renewal is bought, so a sentence also costs the earnings that would have paid for it. Their courts sell renewal back as well: a convict may buy the right to keep renewing while inside. The rich serve time without ageing; the poor age in their cells.
• The Parishad. Prisoners keep free care to 100. After that a court may bar a convict from buying renewal, a softer form of the shortened term.

Births, expansion and the Lines

Long lives make births rarer, but above all they make them unequal. Many people never have children. A minority, freed from biological deadlines, set out to have dozens or hundreds over the centuries. On Earth, that minority, not the average person, drives population growth. Off Earth, where most birth caps have gone, large families are the norm: natural increase there runs at about 0.8% a year, close to the most prolific Lines. Together with emigrants from Earth, they drive the expansion beyond Earth.

What the combination does. A renewed person stays fertile for centuries; gametogenesis makes eggs or sperm from anyone; artificial wombs remove the burden of pregnancy. One person can parent hundreds of children over a long life, with or without a partner. Unrestricted, the arithmetic would be unforgiving: a line growing 3% a year doubles about every 23 years and grows a millionfold in under five centuries. In practice habitat construction, energy, childcare and licences hold even the most prolific Lines to about 1% a year — ten founders in the 2310s become about sixty descendants by 2497 — but over centuries that is enough for a prolific minority to outgrow everyone else.

How societies respond.

• Licensed parenthood. On Earth, most Settlement polities license births — typically a quota per person per century, tied to reserved habitat capacity and tradeable only within the polity that reserved it. The renewal ration and the birth licence are two halves of one bargain. The Parishad allows about two children per couple (see The Parishad). Off Earth, fusion and, increasingly, mirror array power make habitats cheap to build, so the material case for caps has gone; where they survive, they survive for political reasons. Where they have gone, the bargain breaks: a Settlement citizen off Earth gets the same renewal ration and children as well, which is one of the strongest pulls to emigrate.
• Earth is capped; habitats are built. Earth's population is held near eight billion. With lives planned at about 300 years in the Settlement and the Mandate, and averaging about 150 in the Parishad and the Open Cities, that allows under 40 million births a year, less than a third of the 2020s figure. Earth keeps its limits — waste heat, land and the Rotation Laws. The surplus goes outward, to the Belt, Mars, Titan and Jupiter's moons, where habitable volume has to be manufactured but power to manufacture it is plentiful. Pronatalist communities are the most willing colonists, and their numbers, more than any government's ambition, explain why ships kept leaving.
• The Lines. Some long-lived founders are building dynasties: dozens of living descendants so far, on course for thousands. These Lines behave like clans or small nations and own whole habitats. Their votes are still too few to matter; for now they count through their wealth. Their founders are still alive and still in charge, among the first renewed, and the richest bought their way past every ration.
• Designed children. Gametogenesis makes embryo selection and editing routine. Settlement polities allow it, except for edits with unforeseeable consequences and edits not yet proven safe and effective in studies. One condition applies: anyone who edits their own child must pay an equal sum into a public pool, which clinicians spend on edits for poorer families' pregnancies, chosen by need. It narrows the gap without closing it: wealth still buys repeated enhancement, better schooling and the right connections. The pool pays for one generation's edits, chosen by need; a rich family can plan edits across many generations towards a single aim, and that compounding is what the rule cannot match. The families that produce Vault engineers are its clearest result (see Recursive self-improvement). Some Lines and Open Cities impose no limits at all. The Parishad allows editing without the pool, so its Vault engineer families stay a hereditary elite (see The Parishad). Off Earth, editing is how children are fitted to their world. The partial-gravity programme of the 2100s, which let children grow up healthy at Mars's 0.38 g, has grown into routine adaptation for each world: radiation tolerance in the Belt, cold and low gravity on Titan. Almost everyone off Earth is adapted: children before birth, and most adult emigrants by gene therapy when they arrive, which helps less. The Mandate adapts by state plan; the Settlement under the rules above, so an adaptation is allowed once proven safe, and the pool pays for poorer families' children; the Open Cities and the Lines adapt without limits. Populations now differ by world as well as by bloc, and altered people find Earth hard to return to. Whether they keep full rights to migrate to Earth, the Kinship Question, came to a head in the 2450s, when the Belt's independence made it a question of citizenship; Earth decided yes, grudgingly.

Raised persons follow a different pattern of ageing and care. They may live for centuries with maintenance, though their full lifespan is unknown. In the Parishad, Raised parenthood requires an agreement to end life at 150 or emigrate; accepted settlement in a Parishad habitat off Earth or the purchase and permanent surrender of unused birth rights can allow continued life beyond 150 (see Raised lives, in One mind, one form).

Rough population in 2497. Earth about 8 billion (Settlement \~2.3 billion, Mandate \~2.2 billion, Parishad \~1.8 billion, Open Cities \~1.6 billion, buffer \~0.05 billion). Births, not borders, explain the balance: the Open Cities set no birth caps, while many Settlement citizens who want children emigrate off Earth, where they keep the ration and can have children as well. The rest of the solar system about 3 billion, a third of them in the Mandate (Mars \~0.75 billion, the Belt \~1 billion, Titan and Saturn \~0.6 billion, Jupiter's moons \~0.5 billion, the Moon and the outer edge \~0.15 billion); Proxima, settled in the 2390s, about ten thousand. Five colony ships are in flight, and the Lifeboat is braking at Gliese 876 with its embryos still frozen. These figures count people of flesh; about 150 million Raised minds live as well, about 57 million of them in Freehold, the Raised bloc, and most of the rest as Settlement citizens.