A birth
Two parents, one random seed, one child. Below, the whole thing happens in front of you, byte by byte, with real parents from the population. Only the seed is different each time you draw.
What the film says
Two parents. One random seed. One child.
The ledger grows ring by ring. Once a ring has grown, nothing in it changes. The request is sealed into one: these two parents. The seed is drawn afterwards, as a later ring grows: the one that captures the birth. Until then it doesn’t exist, for anyone: not the keeper, not the species. And a request can’t bring a seed of its own. Any of these could be the child. The validators draw it together, as that ring grows. The parents were sealed in before it was drawn. Nobody gets to go back.
The seed drives the reading: it becomes a stream of numbers. Each parent passes on one copy of every gene; the seed picks the copy each group starts on. At every gene a number is drawn; only a very low one switches copy. Then the other parent, the same way. Switches are rare, so genes that sit together travel together. Now and then a gene changes as it is copied: here, one number gene moved a step.
This child took its build from one parent and its colouring from the other, not a random mix of everything.
Same parents, same seed: the same child, every time. Anyone can work it out again from the public record.
A small species, grown from its genome. Choose the parents. Chance chooses the child. Every genome is written on a public ledger.
Two genomes in, one genome out
Each little square is one gene. A moeba has two rows of them, one from each parent. The child’s first row is read along the first parent, the second row along the second parent, and every now and then the reading switches from one of that parent’s rows to the other. It plays on its own; pause it and step through one gene at a time, or point at a square to read it. The seed is real and so is the arithmetic: the same seed always gives the same child.
Eight children from the same two parents
Each card is the child the rules would produce from a different random seed. On the ledger only one seed happens, and nobody gets to pick which. A coloured mark means that draw had a mutation.
Why families have looks
Genes that sit next to each other in a row tend to be read together, because a switch is rare (24 chances in 256 at each step). The body genes travel as a block, the colour genes as another. So a child often has one parent’s build and the other’s colouring, rather than a random mix of everything. The four blocks are the four labelled groups above.
Then mutation
With the two rows read, the same random stream continues. First the mutation routes: rules like “if this row has variant A here, and the rest of the genome allows it, then with a small chance it becomes B”. Mutation routes are the only way some variants ever appear; no founder has them, and they fire rarely. Then drift: each number gene, on each copy, has about a 2% chance to move one step. With 22 number genes in two copies, about six births in ten carry at least one such step somewhere — usually too small to see, since the body follows both copies together. A new variant from a mutation route is much rarer. In the picture, a mutated square has a dot.
What the parents must satisfy
- Both minted by the species’ account, and of the same genetic model.
- Not the same moeba, not parent and child, not full siblings. Half-siblings may breed.
- Both mature: one minute past the moment their own randomness was fixed, on the ledger’s clock. Founders are mature from birth.
- Both with births left. Every moeba is born with five births and spends one per child, as either parent.
- Neither already reserved by another birth in progress.
- The requester keeps one of them, and either keeps the other or is open to breeding at the price paid.
The lab above shows the Hooks’ answer when a pair would be refused.
What to remember
- A child gets one copy of every gene from each parent, read along groups of neighbouring genes, so neighbours tend to arrive together.
- Then mutation routes may change a variant, and each number gene may drift a step.
- The seed decides all of it, and nobody chooses the seed: the same two parents could have had many other children.