Tolerance

GRANT 41,882

skin, split-thickness, 24 cm². Donor: Ostrowska, R. Recipient: Holt, S. (minor). Match: not required.

The summer I was nine I wore another woman’s skin on my forearm. I had put my arm through the lagging of a steam line, and a quarry worker named Ruta Ostrowska, who was in the clinic that afternoon with grit in her eye, lay down on the next table and gave the dresser a piece of her thigh the size of a playing card. Nobody asked whether we matched. The question did not exist here. The graft took the way turf takes, and by autumn it was simply my arm: a patch paler than the rest of me, hers and mine and nobody’s.

That is the commons. If you were born under it, you cannot make it sound as strange as it is.

There were eight hundred and twelve founders, one medical bay, and no supply chain behind them. The geneticists who drew up the colony understood exactly what tissue rejection costs a small population: it costs an industry. Immunosuppression is not a drug, it is a civilisation — assays, refrigeration, registries, the luxury of choosing among donors — and they were not bringing a civilisation. So they did what an engineer does with a fastener she will have to trust for centuries: they standardised it. Every founder’s germline was set homozygous for one tissue type, the great antigens and the small ones alike, a single weave for the whole colony. Any skin would cover any burn. Any marrow would seat in any blood. A kidney became a part, like a bearing, and the store of parts was everyone.

Growing up inside it, you did not call it generosity, any more than you call the air generous. Children gave marrow the way they gave outgrown boots. The word stranger survived only in old books, and in medicine it meant nothing at all.

The founders were not naive about gifts, either. A gift that cannot be rejected is a gift that cannot be stopped. A bag of donated blood is full of living white cells, and in a commons those cells do not die quietly in another body’s veins — they can settle, multiply, take the new body for territory. So every unit passed under the irradiator on its way to the shelf, and came out alive enough to carry oxygen and too broken to divide. We knew, in other words. We knew that flesh which is welcome everywhere goes everywhere. We put a gate on the one road we had thought of.

The register I keep was designed on Earth, where its keeper would have been called a matcher. The title came down to me with nothing left to match. I record grants — skin, marrow, blood, corneas, one whole liver in the year I was born: donor, recipient, site, date. Match: not required. Seventy thousand entries, each one a small proof that the founders had been right.

Dr Amadi brought me two slides on a winter morning, because the register is where you go to ask who has touched whom.

Two men with the same leukaemia. Not the same kind of leukaemia — the same leukaemia: blasts with the same broken karyotype down to the band, the same private mutations, in two men who had never shared a room. The laboratory assumed contamination and ran it three times. Then someone thought to check the malignant cells against the men they were killing, and found that the marrow growing in both of them belonged to neither.

It belonged to Vera Lindqvist, dead sixty-one years.

She is in my register two hundred and fourteen times. Blood, mostly, and that road was gated: irradiated cells cannot found anything. But she gave skin four times, and skin goes on warm and living, with her white cells still walking through it. She gave marrow twice, and marrow is the gift that is nothing but founding. And in the quarries there has always been a practice the register only half records — warm blood, arm to arm, at the rock face, when the shelf is an hour away and a man is emptying faster than that. The second marrow grant is where the trail begins. That recipient recovered, lived long, and gave for thirty years while the thing slept in him. So did others. A leukaemia is slow arithmetic, and some of the carriers died of age before it finished — but they gave while they carried. I spent that winter learning that the book in my lap was not a record of gifts. It was the epidemiology.

In the founding memoranda, appendix C, there is a hazard table, and in the table there is a row. Neoplasm, transmissible. A malignancy arising in any colonist will be self to all; it may pass as a graft passes. Likelihood low; expected burden negligible against benefit. They had known. It is what honest engineers write when they have decided to take a bet: the failure mode, priced, initialled, filed. The bet paid for a hundred and thirty-nine years.

Amadi went to the old library for precedent and found two. A marsupial on Earth, an island carnivore whose tissue types had drifted so close together that a facial tumour began passing from bite to bite, and nearly ended the species inside twenty years. And the dogs. There is a tumour that has been travelling from dog to dog for eleven thousand years, since before the plough — the oldest living dog tissue in the world, and it has not been a dog for most of that time.

We sequenced the Lindqvist clone out of eleven living carriers. It has shed a third of her chromosomes, and what it has kept, it has kept because keeping it helped it stay. It is not Vera Lindqvist. It is what tissue does when nothing tells it no.

Anywhere else in our species, none of this could have happened. Two strangers can pass warm blood between them for a lifetime, and the passenger cells are found and killed inside a week, every time, without either of them ever knowing there was a battle. Rejection — the thing the founders closed like a design flaw — was never a flaw. It was the defence, so old and so complete that no one had ever needed to learn it was there.

What can be done, we did. Every grant is screened now; before any tissue moves, we ask it the new question, the one that replaced matching: are you your donor’s own? The quarrymen have been taught to bleed apart, which they hate. But you cannot recall skin. You cannot retype the living — the weave is written in every cell of every one of us, and the clone reads us all as home. Somewhere between one and three hundred people are carrying it quietly, and the register can narrow that but never close it.

The unborn are another matter.

The vote went four to one. Since that spring, every embryo has its surface antigens drawn again at random — the great ones and the small ones, a fresh hand dealt to each child, the way the rest of the species has always dealt them. The physicians call it restoring diversity. Everyone else calls the children what my register calls them: S-typed. Strangered. Each of them is something this colony has never held before — a body with a border. The clone cannot enter them. Neither can anything else.

GRANT 70,551

skin, split-thickness, 9 cm². Donor: Holt, E. Recipient: Holt, M. (minor). Match: FAILED. Grant declined.

That entry is my daughter offering her thigh, and the register refusing her, and my granddaughter healing under dressings for six weeks instead of six days. It is the first failed match in the history of the book. There will not be many more entries of any kind for the S-typed; that is the point of them, and the price of them. If Mara ever needs marrow, there is no one on this world who can give it to her, and we no longer own the civilisation that would let her accept it anyway. The founders traded that vulnerability away for us, and we have handed it back to our children on purpose, because it turned out to be load-bearing.

The clone, for its part, is running out of world. It cannot cross into anyone born after the Draw. The commons is a closed cohort now, ageing together, and the disease that lives in us has exactly our life expectancy. My blood still goes to the shelf with the red band, commons stock, for the shortening queue of people who can use it. The shelf and the queue will empty in the same decade.

GRANT 71,116

whole blood, one unit. Donor: Holt, S. Recipient: unassigned, commons stock. Match: not required. Note: closed shelf.

Mara turned nine this spring — the age I was when I met Ruta Ostrowska’s thigh. The scald on her hand has gone silver, raised, hers all the way down. Last week she noticed the patch on my forearm, still paler than the rest of me after sixty years, and asked what it was. I told her whose it was. She looked at my arm for a long time, and then at her own hand, and I watched the question not occur to her.