◄ WORLD V · SONNY 5DART 595 · a helldive into the living

THE QUASISPECIES the edge where information melts

A replicating molecule that copies imperfectly cannot grow its genome without limit. Eigen showed an error threshold: information survives only while the genome length times the error rate stays below about one — roughly Lmax ≈ 1/μ. Past it, mutations accumulate faster than selection can prune, and the sequence dissolves into a quasispecies — a cloud of mutants around a consensus — then into noise. RNA viruses live perched right at that edge.

THE TECHNIQUE Lmax ≈ 1/μ ; beyond it, error catastrophe

The demo computes the maximum genome length for an error rate and shows what survives vs melts: live demo







  
HISTORY & CREDIT Manfred Eigen · 1971

  
“Higher mutation always speeds evolution.” — past the error threshold it destroys information (error catastrophe); antivirals like lethal mutagenesis push viruses over it on purpose. cited

  
the cloud · imperfect copying makes not one sequence but a quasispecies around a consensus.
the threshold · information survives while μ·L < 1 (Lmax ≈ 1/μ); beyond, it melts.
1971 · Manfred Eigen — why RNA viruses sit at the edge.

  
Copy a little wrong and the message survives; too wrong and it dies. origin of life






  
RECOMMEND FOR I-13 the threshold, on the compiler

  
On i-13, error rate 1/100 gives Lmax=100: length 80 survives, 150 melts (catastrophe):

  
$ i13 run lf_quasispecies.i13
RUN OK · 22 step(s)
l_max = 100   -- 1/mu
survives(80) = 1   catastrophe(150) = 1

  
Recommend as a NULL — a threshold theorem (B39). Lmax≈1/μ is a pinned bound; the catastrophe is a phase boundary, not a same-function DOF. NULL — the edge where information melts.