What outlives what
inverted
A human body replaces its gut lining every few days and most of its
cells within years, yet persists for decades. A company's servers last about
five years — and the company itself now lasts around fifteen.
In biology the parts are disposable and the whole endures. In computing it is closer to
the reverse.
The two ladders, shortest first
Life
Computing
~20 minutesbacterial division, under ideal conditions
~64 msDRAM refresh interval — state survives only by being rewritten
3–5 daysintestinal epithelium
hours–daysa container instance, in anything autoscaled
~120 daysred blood cells
~2–5 yearsa major framework version, before migration is forced
~1 yearmost of the liver
3–5 yearsserver refresh cycle; SSD endurance rating
~10 yearsthe skeleton, remodelled entirely
15–20 yearsa data-centre building
a lifetimeneurons and cardiomyocytes — largely never replaced
~15 yearstenure in the S&P 500
~73 yearsa human, global mean
~45 yearsTCP/IP — the oldest thing still running unchanged
10⁶–10⁷ yearsa typical species, before extinction or divergence
—no counterpart: nothing in computing is old enough to have a lifespan yet
What these figures count
- counts
- Typical replacement intervals, not maxima. Corporate tenure is time in the S&P 500 index, not company age.
- excludes
- The rows are ordered by duration, not paired by kind. A DRAM refresh and a bacterial division are both "the fastest thing on that side" and nothing more — the pairing is positional, not causal.
- uncertainty
- Index tenure is a forecast and has been revised repeatedly: Innosight's figures fell from 61 years in 1958 to 24 by 2016, with ~12 projected for 2027, while other trackers put the current figure nearer 15. Species lifespans vary by orders of magnitude between taxa.
- the trap
- Index tenure is not corporate mortality. A company leaving the S&P 500 has usually been acquired or has shrunk, not died. It measures churn in a ranking — a proxy for disruption, not a lifespan.
Continuity through replacement
Biology solved a problem computing has not. A body maintains identity while almost every
atom in it is exchanged. There is no migration window, no cutover weekend, no version
freeze. Replacement is continuous, piecewise, and invisible from outside.
The mechanism is the one the energy page
is about: every component is
maintained by ongoing expenditure, and anything that stops being paid for is recycled.
Persistence is not a property of the parts. It is a property of the loop that keeps
replacing them.
Note the exception, because it is the tell: the cells that mostly do not turn over are
neurons and cardiomyocytes — the ones holding state that cannot be reconstructed.
Everything reconstructible is disposable. Biology replaces anything it can regenerate
from a specification, and preserves only what it cannot.
That is a design rule, and it transfers directly. A system whose specification is written
down can afford to treat its running parts as consumable. One whose behaviour lives only in
the parts cannot — which is why an agent architecture that keeps its spec in a document and
its state in a ledger is not bureaucracy. It is the thing that makes the components
replaceable.
Sources
- Innosight, Corporate Longevity Forecast — average S&P 500 tenure 61 years in 1958, 24 by 2016, ~12 projected for 2027. innosight.com
- Current average tenure ~15 years. Apollo Academy
- Cell turnover intervals are standard physiology values, consistent with the
ai-bio-energetics catalogue's substrate-store entries. - Server refresh at 3–5 years is the common depreciation and replacement cycle, not a measured mean lifetime. DRAM refresh interval is a JEDEC specification.
- Species lifespan of 10⁶–10⁷ years is a broad palaeontological average spanning wide taxon-level variation.