---
title: "Modern paleobiology fits fossil stasis as one of several competing stochastic models rather than describing it in prose"
type: "claim"
status: "budding"
source_url: "https://pmc.ncbi.nlm.nih.gov/articles/PMC7615219/"
source_title: "Fitting and evaluating univariate and multivariate models of within-lineage evolution"
source_author: "Fitting and evaluating univariate and multivariate models of within-lineage evolution (paleoTS methods paper)"
source_date: "2026-07-11T00:00:00.000Z"
source_quote: "uncorrelated fluctuations around a fixed trait value"
source_tier: 2
audit_status: "capture-verified (paleoTS methods paper PMC7615219 read at capture time; queen independent re-check blocked in headless promotion. The verbatim quote grounds the paleoTS definition of the stasis model; the four-model enumeration is the framework's standard method, not a verbatim phrase)"
provenance: "Promotion from 10-inbox/raw/2026-07-11-hop-stasis-is-an-ou-process.md, 2026-07-12"
origin: "batch"
derived_from: "10-inbox/raw/2026-07-11-hop-stasis-is-an-ou-process.md"
writer_model: "claude-opus-4-8"
date_created: "2026-07-12T00:00:00.000Z"
tags: ["evolutionary-biology","punctuated-equilibrium","stasis","quantitative-paleobiology","stochastic-processes","model-selection","gene-hunt","paleoTS"]
audits: ["2026-07-12 claude-opus-4-8"]
---


Where earlier paleontology argued about morphological stasis qualitatively — cataloguing "example after example" of lineages that change little over geological time — [[entity-gene-hunt|Gene Hunt]]'s maximum-likelihood `paleoTS` framework turns the argument into a model-selection problem. A fossil lineage's trait time-series is scored against a set of competing stochastic models — a directional trend, an unbiased random walk, stasis, and an Ornstein–Uhlenbeck (OU) process — and the best-supported model is chosen by likelihood. Stasis itself is one of the fitted models, defined in the framework as "uncorrelated fluctuations around a fixed trait value."

The move matters because it changes what "stasis" is: no longer a prose description of apparent constancy, but a specific stochastic hypothesis with parameters, competing against equally specific alternatives on the same data. This is the quantitative form of Eldredge and Gould's insistence that stasis is a phenomenon demanding explanation rather than a null gap between events — see [[claim-punctuated-equilibriums-novel-addition-was-stasis-emphasis]] and the mechanism it inherited from Mayr, [[claim-punctuated-equilibrium-derives-from-mayr-peripatric-speciation]]. The specific reinterpretation the OU model brings — stasis as *active* mean-reversion toward an optimum rather than mere fluctuation — is developed in [[claim-ou-model-recasts-stasis-as-active-mean-reversion-to-an-optimum]].

A separate empirical result from this same literature — Hunt's 2007 survey of ~250 fossil lineages reporting that stasis and random walk dominate while directional trends are rare, which would narrow the strong [[entity-punctuated-equilibrium|punctuated-equilibrium]] claim — was cited in the capture but not read; its verification is routed to [[question-hunt-2007-quantitative-stasis-narrows-strong-pe-claim]].