Environment — the drive h (sets and remembers, within a fixed SET)

The environment never rewrites the genome; it sets h via methylation (CpG handles 11–179) and temperature (fixed γ, flip ×4) within a fixed SET. Reversible.

ENVIRONMENT is the tilt h the environment sets on R19. It sets and remembers STATE/DWELL within a fixed SET — it cannot rewrite SET or γ. The primary readable mechanism is DNA methylation: the CpG count is the number of writable handles, ~11–179 per switch (16×). At fixed γ the flip rate changes ~4× with temperature. Methylation is heritable and reversible, so the mutable part is bounded by the fixed SET.

What ENVIRONMENT is

ENVIRONMENT is the runtime drive h on R19: ṡ = −(s³ − γs − h). The environment (temperature, water, nutrition, stress, social signal) sets h, biasing whether a switch turns on (STATE) and how long it stays (DWELL), and — via molecular marks — remembers that bias. It is Layer-2: it sets and remembers, but does not change the readable hardware (SET, position, γ).

Mechanism — moving a switch without changing the sequence

DNA methylation — the primary readable mechanism. In animal genomes the mark is 5-methylcytosine at CpG; it changes local accessibility, binding, and effective stiffness, biasing h. It is readable: the CpG count is the number of writable handles on a switch. Measured across switches, CpG handles span ~11 (frog UCP1) to ~179 (chicken UCP1) — a 16× range; CpG-island switches are highly tunable, CpG-poor switches nearly hard-wired. So how open a switch is to the environment is itself read from the sequence. The mark is heritable through cell division (hysteresis = memory) and reversible: genetically identical individuals enter diapause epigenetically, transmitted for ~3 generations.

Temperature — a physical mechanism. The R19 barrier γ²/4 is fixed by the sequence, but the flip rate ∝ exp(−barrier / noise(T)). At a fixed γ=1.41 (barrier 0.497, unchanged), as effective temperature rises the same switch flips ~4× more often. Hardware unchanged; the environment changed only the drive.

The environment re-sets within a fixed SET

• Salamander timing trigger: developmental timing correlates with dry climate / low water — an environmental drive setting how long the embryo develops inside.
• Vernalization: cold sets a plant's flowering switch (FLC silenced via methylation) — the environment remembers a STATE.
• Temperature-dependent sex (TSD): egg temperature pushes the gonad STATE switch past spinodal — the environment flipping a Layer-1 STATE.
• Bee caste: nutrition (royal jelly) → methylation difference → queen/worker.

The boundary — ceiling is SET, reversible

The environment sets h and remembers via methylation; it can push STATE past spinodal (TSD). But it cannot rewrite SET or γ — those are fixed. So environmental adaptation re-sets STATE/DWELL within a fixed SET, and is reversible (a mark can be erased). The fixed SET is the ceiling: the mechanism re-tunes switches that exist; it does not make new ones. (On origin and history this paper is silent — see the Constitution.)

Failure log

• Causality largely correlative: methylation→phenotype is mostly correlative in the literature; the exact h-shift per mark is open. We report the CpG-handle range, not a quantified causal effect.
• Salamander plastic vs fixed unresolved: real-time plasticity vs a population-fixed difference is not cleanly resolved; the mechanism-confirmed clean cases are diapause, TSD, vernalization, bee caste.
• CpG count ≠ realized methylation: the handle count is readable; the realized state is runtime.