When does improvement become invention?

I wanted to see it for myself

This is an old question in artificial life. In 2003, Lenski, Ofria, Pennock and Adami used Avida to show complex computational functions building on simpler functions that had evolved earlier. I had a much smaller world with traceable lineages and replayable history. I wanted to see how far I could get.

THE NOTE

An artificial ecology can change. It can adapt. It can discover things that help.

But does anything new become the foundation for what comes next?

In Cell80, organisms carry small programs as genes. Those programs help determine when they eat, how they move and when they reproduce. Offspring inherit programs and numerical settings, with mutations. Some lineages leave more offspring than others.

In the first note, I traced a population shift to a birth and tested what happened when one inherited change was undone. The second asked what kept predators and grazers alive long enough for evolution to continue.

Here I use replay to ask a different question: did a mutation help its carrier reproduce, and did a later advantage depend on it?

I completed a batch of 379 primary worlds, with additional verification runs, to separate several claims that are easy to collapse into one story.

Change → benefit → novelty → succession → dependence

Each requires evidence of its own.

01 / CHANGE

A mutation happens.

An offspring receives a different movement program, or a different threshold for reproduction. Its genome is now different from its parent's.

This is the easiest step to produce. A changing genome tells us that variation exists. We still have to find out what that variation does.

8 of 108 tested composition changes helped.

I tested changes that replaced an existing movement gene with a composition of library programs. In eight cases, the focal organism produced more direct offspring than it did when that change was undone. Eighty-four cases tied; sixteen produced fewer.

These were local advantages, measured in particular birth contexts over a fixed horizon. They establish that some composed genes can help in this ecology.

The compositions themselves were generated before the worlds ran. Evolution encountered a prepared pool of possibilities; it did not write these programs during the experiment.

5 of the 8 helpful compositions repeated an existing behaviour.

A program can contain different code and still make the same decisions.

The movement input in this world is small enough to check exhaustively: three food readings, each either zero or forty. That gives eight possible input combinations.

Across all eight, five helpful compositions chose exactly the same immediate actions as a gene already in the library. Even the composition with the largest offspring gain repeated an available behaviour.

Three helpful compositions had distinct action signatures in this domain. That is a specific, bounded kind of novelty. The check concerns immediate movement actions; it does not establish equivalence of execution costs or future mutation possibilities. It was also a later diagnostic, separate from the registered acceptance tests.

2 candidates contained a later beneficial change.

I followed descendants that retained a helpful composition and tested subsequent numerical mutations. Of 72 tested changes, two increased the focal organism's direct offspring count.

One altered how much energy a parent passed to its offspring. The other lowered the reproduction threshold.

There was now a sequence worth investigating: a helpful composition, inherited along a lineage, followed by another helpful change.

Getting better twice raises a further question. Did the first improvement contribute to the value of the second?

Neither candidate passed.

For each candidate, I tested four combinations in fresh worlds: the original genes, the first change alone, the second change alone, and both changes together.

The registered test asked whether the later mutation helped more with the composed movement gene than with the original movement gene. That interaction had to be positive in at least four of five held-out worlds, and positive on average.

One candidate had positive interaction in three worlds. The other had it in none.

The assay used whole founder populations in fresh environments, so it answers a different question from replaying a single birth in the ancestral world. Under that assay, neither sequence established the registered dependence claim.

There is also a stronger question beyond this test: would the later mutation have been advantageous at all without the earlier change? A positive interaction alone would not settle that.

06 / THE RATCHET

Independent replication and a further dependent step remain open.

Getting better isn't the same thing as building on what came before.

After EX-10, I built a different world with new food. No existing program could process it alone, but a combination could. Two further notes follow that experiment and the fate of the organisms that inherited this capability.

EX-10 did not establish dependence. EX-11–14 now support a bounded opportunity and its transmission, followed by a positive conditional effect in one descendant’s ecology. A chain with a further dependent advance and open-ended evolution remain untested.

EX-11 checked all 89 typed primitives against the resource and evaluated 1,825 compositions generated during mutation. One expression passed. The capability appeared in 3/10 full worlds and persisted in 2/10, but there were no later uptake mutations eligible under the registered establishment rule. Conditional dependence was untested in that experiment.

EX-12 selected the first clean capability-to-uptake candidate at birth in fresh worlds. One of four passed both the historical-opportunity and standardized dependency screens, but left no offspring in its original history. The requirement of three independent discovery cases was not met.

EX-13 found one supported opportunity among five candidates. It transmitted both changes and had 148 intact descendants at +200 ticks and 230 at +500. The checkpoint dependency effect was positive in 6/10 futures and tied at zero offspring in four, failing the unchanged 8/10 gate. Transmission was observed; full-gate retention remained unsupported at 0/1.

THE EARLIER RECOVERY CLAIM

The earlier numerical recovery “ratchet” is separate from cumulative capability dependence. Extending the no-swap condition from five seeds to ten lowered mean recovery from 0.505 to 0.359. No tested full-role dose reached the registered 0.5 threshold. This genome endpoint is not reproductive fitness.

EX-14 / A chance to reproduce

EX-14 tested 100 matched futures from one descendant’s world. B keeps the food-processing program; BC also keeps higher food intake. BC’s family reproduced in 64/100 futures. It produced more births in 63/64 futures where either version reproduced: mean gain 99.45 births, median 4. Both sources agree on these counts. The 36 futures without reproduction still count toward the total.

Source discrepancy / 10 September 2026

The database conclusion and report say B reproduced in 41/100 and the remaining conditional case was a loss. Recalculation of the local ex14.jsonl gives B as 22/100, one reproductive tie, and no conditional loss. The visual uses local raw outcomes and the original summaries are preserved alongside them. The discrepancy remains unresolved; neither source has been silently corrected.

EX-15 / Replication pending

The database marks EX-15 running, with no reported outcome. It seeks at least three independent opportunities that pass birth-time dependency, transmission, checkpoint persistence and later conditional-effect support. One checkpoint is not a general probability for Cell80. Accumulation beyond this dependency, historical necessity and environmental mediation remain untested.