Baker's Yeast

Baker's yeast proves that the molecular machinery of aging is ancient - conserved across a billion years of evolution separating yeast from humans. Restrict calories in yeast, and their replicative lifespan extends 30%: from 15 cell divisions to 20. Engineer yeast with an extra SIR2 gene (the sirtuin homolog), and they live 30% longer even without caloric restriction. The implication is profound: sirtuins alone are sufficient for longevity. The mechanism isn't unique to complex organisms - it's fundamental to cellular biology.

But yeast reveals something else critical: stress-responsive mutation. Like bacteria, yeast increases mutation rates under stress - providing evidence that stress-induced mutagenesis evolved independently in eukaryotes. This isn't molecular coincidence; it's a selected trait. When conditions are terrible, conservative replication strategies preserve failure. Increasing mutation rate is a bet on variation - most mutations fail, but some might stumble on a solution the parent genotype couldn't reach.

The strategic principle cuts against intuition: In stable environments, minimize variation. In crisis, maximize it. Yeast teaches that successful adaptation requires recognizing which mode you're in. Most organizations do the opposite - they enforce rigid processes during crisis (when variation might save them) and tolerate chaos during stability (when consistency would compound gains).